Fire Alarm Signal Recognition

Proulx, G.; Laroche, C.; Jaspers-Fayer, F.;Lavallée, R.

IRC-IR-828

www.nrc.ca/irc/ircpubs

NRC-CNRC

Fire Alarm Signal Recognition

Guylène Proulx, Chantal Laroche, Fern Jaspers-Fayer andRosanne Lavallée

Internal Report No. 828

Date of issue: June 2001

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Fire Alarm Signal Recognition

Authors affiliations:

Guylène Proulx, Ph.D. and Fern Jaspers-FayerFire Risk Management ProgramInstitute for Research in ConstructionNational Research Council Canada

and

Chantal Laroche, Ph.D. and Rosanne LavalléeAudiology and Speech-Language PathologyFaculty of Health SciencesUniversity of Ottawa

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Fire Alarm Signal RecognitionG. Proulx, C. Laroche, F. Jaspers-Fayer, R. Lavallée

TABLE OF CONTENTS

ACKNOWLEDGMENTS ……………………………………………………………………… v

EXECUTIVE SUMMARY …………………………………………………………………….. vi

RÉSUMÉ ..……………………………………………………………………………………… viii

1.0 INTRODUCTION ..………………………………………………………………………… 1

2.0 LITERATURE REVIEW …………………………………………………………………. 2

3.0 RESEARCH OBJECTIVES ..……………………………………………………………. 5

4.0 METHODOLOGY ………………………………………………………………………… 6

4.1 Participants ……………………………………………………………………….. 6

4.2 Signals Tested ……………………………………………………………………. 7

4.3 Materials ………………………………………………………………………….. 9

4.4 Procedure ……………………………………………………………………….. 10

5.0 STUDY RESULTS ………………………………………………………………………. 11

5.1 Respondent Profile ……………………………………………………………… 11

5.2 Merging Data from the Three CDs ……………………………………………. 13

5.3 Signal Recollection ……………………………………………………………… 14

5.4 Signal Identification ……………………………………………………………… 15

5.5 Signal Recollection and Identification …………………………………………. 17

5.6 Signal Perceived Urgency ……………………………………………………… 20

5.7 Signal Identification and Perceived Urgency ………………………………… 21

6.0 CONCLUSIONS …………………………………………………………………………. 22

7.0 RECOMMENDATIONS…………………………………………………………………. 23

8.0 FUTURE WORK ………………………………………………………………………… 26

9.0 REFERENCES ………………………………………………………………………….. 28

APPENDIX 1: Spectrum Analysis of the Signals Tested ………………………………… 30

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LIST OF TABLESTable 1: Signal Presentation Order on Each CD………………………………………….… 8

Table 2: Population Distribution of Canada and Study Sample…………………………… 12

Table 3: Results to the T-3 Signal for Each CD ……………………………………………. 13

Table 4: Number of Occupants who Confirmed Having Heard a Signal Before………… 14

Table 5: Number of Occupants who Correctly Identified Each Signal…………………… 16

Table 6: Wrong Identification of the Temporal-Three ……………………………………… 19

Table 7: Difference in Perceived Urgency between T-3 and Other Signals……………… 20

Table 8: Identification of any Signal as a Fire Alarm and Perceived Urgency …………. 21

LIST OF FIGURESFigure 1: Gender and Age Distribution of the Study Sample………………….………… 12

Figure 2: Recall Percentage of Each Signal ……………………………….……………… 15

Figure 3: Percentage of Signals Identified .……..…………………………….…………… 17

Figure 4: Recollection and Identification of the Temporal-Three………………………… 18

Figure 5: Percent of Each Signal Recalled and Identified Correctly……………………. 18

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Acknowledgements

This project could not have been possible without the support of Mr. Arnold Garson, Vice

President of Industry Affairs, Siemens Building Technologies Limited. Mr. Garson readily gave

his support to conducting a study of the Temporal-Three signal and his enthusiasm for

furthering the knowledge of fire alarms and life-safety was greatly appreciated. We would like to

thank both him and his organization for their support and hope that we will collaborate on other

productive projects in the future.

We would also like to thank Mr. Mark Faubert and Mr. Bill Thistle, responsible for fire

safety and security at the Ottawa International Airport, for allowing us to gather data at the

airport. After passing the security check, the waiting area of the airport was an ideal location to

ask people to participate in our study.

As well, we would like to thank Stéphane Denis, Groupe d’Acoustique de l’Université de

Montréal (GAUM), who created the three CDs that present the warning signals that were tested

during the experiment. These tools were an essential part of our study. Mr. Denis was also

responsible for the analysis of the acoustical characteristics of the warning sounds.

We would also like to thank Dr. Russell Thomas, Director of the Fire Risk Management

Program at the National Research Council Canada, for his guidance in the statistical analysis of

our data.

Finally we wish to thank our participants. These busy people graciously agreed to provide

not only fascinating data by answering our survey, but also useful insights into our research

through their astute comments.

This work was jointly funded by Siemens Building Technologies Limited and the National

Research Council Canada (NRC).

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Executive Summary

The 1995 National Building Code of Canada requires that fire alarm signals sound the

Temporal-Three (T-3) pattern, as defined by the ISO 8201 “Acoustics – Audible Emergency

Evacuation Signal”. This sound pattern has also been required by NFPA 72 since July 1996. It

is intended that the T-3 pattern will become the standardized alarm signal heard around the

world that will unequivocally mean “evacuate the building immediately”. Although new and

refurbished buildings have, for the past 5 years, been equipped with this new signal, no formal

public education has taken place to inform building users about the meaning and response

expected from them when it sounds. In North America, discussions are ongoing regarding the

necessity to develop a public education campaign on the subject of this new evacuation signal,

and whether an automatic recorded message should follow the signal to prompt the public to

evacuate. As a first step, we need to ascertain if the public already recognizes this sound as an

evacuation signal.

The objectives of this project were to assess the public’s recollection, identification and

perceived urgency of the T-3. Data was collected through a field study. Six alarm signals were

recorded on a CD: the T-3, a Car Horn, a Reverse or backup alarm, a fire alarm Bell, the Slow

Whoop alarm, and an industrial warning Buzzer. The presentation orders of the signals were

different on each of the three CDs used to collect data. Members of the public were

approached in buildings such as shopping centers, office buildings, libraries and airports; they

were then asked to listen through headphones to the different sounds. After each signal, the

interviewer asked three questions: “Have you heard this sound before?”, “What do you think this

sound means?” and finally, “How urgent do you feel this sound is on a scale from 1 to 10? 1

means the sound is not urgent at all and 10 means it is extremely urgent.” The first question

tested recollection of the signal, the second tested the ability of the participant to correctly

identify the signal, and the last question rated the perceived urgency of the signal. It was

heavily emphasized to participants that the sounds heard on the CD were from in and around

large buildings, such as the one where they were in at the time of the interview.

In total, 307 participants, representative of the Canadian population in terms of gender

and age distribution, were interviewed for the study. Results showed a significant difference

between how often participants said they could recall the various signals, Q(5,307)=288.15,

p<.001. The Car Horn was recalled the most often, by 97% of the participants, followed by the

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Reverse alarm by 91%, the Buzzer by 81%, the T-3 by 71%, the Bell by 58% and the Slow

Whoop by 52% of the participants. Respondents who said they had heard a signal before,

however, did not necessarily identify the signal correctly. In fact, the T-3 was identified correctly

only 6% of the time as a fire alarm. The Car Horn was identified correctly 98% of the time, the

Reverse alarm 71%, the Bell 50%, the Slow Whoop 23%, and the Buzzer 2% of the time. There

is a significant difference between the identification of all the signals; x2(5, 307)=555.52, p <

0.001. Consequently, although the participants often reported that they had heard the T-3

before, they could rarely correctly identify it as a fire alarm or evacuation signal. In fact, the T-3

was usually associated with domestic signals such as a busy phone signal or the sound of an

alarm clock.

When asked to rate the urgency of each of the signals, participants rated the T-3 as the

least urgent of all signals. The T-3 received an overall rating of 3.97 on a scale of 1 to 10 (10

being extremely urgent). The Buzzer, Car Horn and Reverse signals received urgency ratings

between 4.91 and 5.60, while the Slow Whoop obtained a rating of 6.01 and the Bell 7.17. It

should be stressed that generally, when a participant identified a signal as a fire alarm, the

urgency rating significantly increased. This finding demonstrates a clear link between the

meaning attached to a signal and the perceived urgency of that signal.

These findings suggest that considerable public education is necessary to improve the

public’s identification of the T-3 signal.

It is further suggested that it is unrealistic to believe that building occupants will start to

evacuate a building as soon as they hear an alarm signal, even if the signal is recalled and

identified correctly as a fire alarm. Supplementary information conveyed through a voice

communication system or by staff will always be needed to confirm to occupants that an

evacuation or relocation is needed. Finally, it is advocated to use the T-3 uniformly as the fire

alarm signal in all buildings, whether the egress strategy in place calls for evacuation or not, to

limit the number of warning signals and therefore improve recognition. With proper training and

sufficient exposure, the T-3 could become the standard fire emergency warning signal, which

occupants will recognize. To receive such a warning is in itself an essential piece of information

to convey to the public before they are instructed to apply specific behaviour during a fire

emergency.

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RÉSUMÉ

L’édition 1995 du Code National du Bâtiment du Canada (CNBC) exige que les alarmes

incendie émettent le signal du Temporal-Trois (T-3), tel que défini par la norme ISO 8201

"Acoustics-Audible Emergency Evacuation Signal". Ce patron sonore est également exigé par

le NFPA 72 depuis juillet 1996. Il est prévu que le patron sonore du T-3 qui signifie "évacuer

l’édifice immédiatement", devienne le signal sonore standard pour l’évacuation au niveau

international. Malgré l’installation depuis 5 ans de ce nouveau signal à l’intérieur de tous les

édifices neufs ou rénovés qui ont pour exigence, selon le CNBC, d’avoir un système d’alarme

central, aucune campagne officielle de sensibilisation n’a été entreprise pour informer le public

de la présence de ce signal sonore et du comportement à adopter suite à son déclenchement.

En Amérique du Nord, les discussions se poursuivent concernant, d’une part, la nécessité d’une

campagne de sensibilisation pour ce nouveau signal et, d’autre part, la nécessité de faire suivre

systématiquement ce signal par un message enregistré encourageant l’évacuation. Dans un

premier temps, il s’avère justifier de déterminer si ce patron sonore est présentement reconnu

comme un signal d’évacuation par le public en général.

Les objectifs de la présente étude étaient d’évaluer la reconnaissance, l’identification et la

perception d’urgence du T-3. Des données ont été recueillies dans le cadre d’une étude sur le

terrain. Six signaux avertisseurs ont été enregistrés sur un disque compact : le T-3, un klaxon,

une alarme de recul, une cloche d’incendie, le Slow Whoop, et un ronfleur industriel. L’ordre de

présentation des signaux sonores était différent sur chacun des trois disques compacts utilisés

pour la cueillette de données. Des membres du public ont été approchés dans des édifices

telles que des centres d’achats, des édifices à bureaux, des bibliothèques et des aéroports et

ont été invités à écouter les différents signaux à l’aide d’écouteurs. Après chaque signal, trois

questions étaient posées au participant : "Avez-vous déjà endendu ce signal auparavant? ",

"D’après vous, quelle est la signification de ce signal? " et finalement, "Quel degré d’urgence

associez-vous à ce signal sur une échelle de 1 à 10 où 1 représente pas du tout urgent et 10

extrêmement urgent?" La première question vérifiait la reconnaissance du signal, la seconde

vérifiait la capacité du participant à correctement identifier le signal, puis la dernière question

évaluait le degré d’urgence perçu par le participant à l’écoute du signal. L’expérimentateur

insistait auprès de chaque participant sur le fait que le disque compact contenait des signaux

pouvant être perçus à l’intérieur et autour de grands édifices, tels que celui où le participant se

trouvait au moment de la cueillette de données.

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Un total de 307 individus a participé à cette étude. Ceux-ci sont représentatifs de la

population canadienne en genre et en distribution d’âge. Les résultats révèlent une différence

significative entre la fréquence à laquelle les participants rapportaient reconnaître les différents

signaux sonores, Q(5,307)=288,15, p < .001. Le klaxon a été reconnu par 97% des

participants, soit le taux de reconnaissance le plus important, suivi par la reconnaissance de

l’alarme de recul par 91% des participants, le ronfleur industriel par 81%, le T-3 par 71%, la

cloche d’incendie par 58% et le Slow Whoop par 52% des participants. Toutefois, les

participants ayant rapporté reconnaître un signal n’ont pas nécessairement identifié celui-ci

correctement. En effet, le T-3 n’a été correctement identifié comme alarme d’incendie que dans

6% des cas. Le klaxon a été correctement identifié dans 98% des cas, l’alarme de recul 71%,

la cloche d’incendie 50%, le Slow Whoop 23%, et le ronfleur industriel dans 2% des cas. Une

différence significative entre l’identification des différents signaux a été démontrée; x2(5,

307)=555,52, p < 0.001. Par conséquent, malgré la reconnaissance courante du T-3 par les

participants, celui-ci était rarement correctement identifié comme une alarme d’incendie ou un

signal d’évacuation. En effet, le T-3 était plutôt associé à un signal domestique, tel que le signal

d’un téléphone occupé ou le signal d’un réveil matin.

Lorsqu’on leur demandait d’évaluer l’urgence de chacun des signaux, les participants ont

jugé le T-3 comme le signal le moins urgent parmi l’ensemble des signaux. Le T-3 a reçu un

score moyen de 3,97 sur une échelle de 1 à 10 (10 étant extrêmement urgent). Le ronfleur

industriel, le klaxon et l’alarme de recul ont obtenus des scores d’urgence entre 4,91 et 5,60,

tandis que le Slow Whoop a reçu un score de 6,01 et la cloche d’incendie, 7,17. Il importe de

mentionner qu’en général, si le participant identifiait un signal comme une alarme d’incendie, le

degré d’urgence coté pour celui-ci augmentait significativement. Ce résultat démontre

clairement le lien entre la signification attribuée à un signal et la perception d’urgence que celui-

ci provoque.

L’ensemble de ces résultats suggère qu’une sensibilisation du public est essentielle pour

augmenter le taux d’identification correcte du T-3.

De plus, il semble utopique de croire que la perception d’un signal sonore par les

occupants sera immédiatement suivie par une évacuation de l’édifice, et ce, même si le signal

sonore est reconnu et correctement identifié comme étant une alarme d’incendie. Des

informations supplémentaires transmises par un message provenant du système de

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communication phonique ou par un employé en uniforme seront toujours nécessaires, afin de

confirmer aux occupants le besoin d’une évacuation ou d’une relocalisation dans un autre

secteur de l’édifice. Enfin, il est suggéré que le T-3 soit uniformément utilisé comme le signal

d’urgence incendie dans tous les édifices, peu importe si la stratégie en cas d’incendie en est

une d’évacuation ou non de l’édifice. De cette manière le nombre et la diversité des signaux

d’urgence seront réduits et, par le fait même, la reconnaissance sera ameliorée. Le T-3 peut

devenir le signal d’urgence standard reconnu par le public si les gens sont eduqués en ce sens

et s’ils sont exposés régulièrement au signal. Percevoir un signal d’avertissement est en soi

une information essentielle qu’il est important de transmettre au public, avant que ceux-ci soient

informés sur le comportement à adopter en cas d’incendie.

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Fire Alarm Signal RecognitionG. Proulx, C. Laroche, F. Jaspers-Fayer, R. Lavallée

1.0 INTRODUCTIONThe 1995 National Building Code of Canada requires that any building equipped with a

fire alarm system should sound the Temporal-Three (T-3) pattern as defined by ISO 8201

“Acoustics – Audible Emergency Evacuation Signal” (1987). This sound pattern has also been

required for fire alarm systems and smoke alarms in buildings by NFPA 72 since July 1996.

Before these requirements came into effect, the fire alarm signal in buildings could sound a

large variety of continuous or temporal signals delivered through various devices such as bells,

horns, chimes or electronic apparatuses. This variety resulted in occupants experiencing

difficulty in recognizing the sound of a fire alarm signal among other signals. Interviews by Tong

and Canter (1985) showed that over 45% of a small sample of building occupants were unable

to distinguish fire alarms from other types of alarms. This identification problem can partially

explain why occupants tend to ignore and disregard fire alarms as genuine emergency warnings

(Proulx, 1994; Edworthy, 1994). Another reason to discredit fire alarm signals is the large

number of nuisance alarms investigated by Karter (1998) and the problem of audibility studied in

previous projects (Laroche et al. 1991; Proulx, Laroche & Latour, 1995).

The need to devise a unique fire alarm signal that could be used and recognised

universally was acknowledged many years ago. Since the 1970s, numerous discussions to

develop a standard signal have taken place (Mande, 1975; CHABA, 1975). In the end, experts

finally agreed not to limit the fire alarm signal to any one sound but instead to support

recognition of the signal through the use of a specific sound pattern. The T-3 pattern, described

in ISO 8201, is expected to become the universal standard evacuation signal. It is intended to

be used around the world and to unequivocally mean, “evacuate the building immediately”.

Major fire alarm system distributors in Canada and the United States have been

systematically installing the T-3, as the fire alarm signal, in all new and refurbished public,

institutional, and office buildings for the past 3 years. According to the National Fire Protection

Association’s Director of Public Education, Judy Comoletti, no formal public education has taken

place to inform building users of this new signal, its meaning or the response expected from

occupants upon hearing this signal. In North America, discussions are ongoing regarding the

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necessity to develop a public education campaign on the subject of this new evacuation signal.

It is also discussed, whether an automatic recorded message should follow the signal to prompt

the public to evacuate. Some people are suggesting that the temporal content of this alarm

might be sufficient to trigger an evacuation response since urgency can be indicated by the

acoustical structure of an alarm signal (Edworthy et al. 1995; Haas & Casali, 1995). As a first

step, we need to ascertain if the public already recognizes this sound as the evacuation signal

and if people associate some level of urgency to this signal that would prompt them to move

during an emergency.

2.0 REVIEW OF LITERATUREWarning signals are commonly used to convey information, both urgent and

inconsequential. The relationship existing between warning signals and their significance has

been of interest for many researchers. Over the past decade, the works of Edworthy and

collaborators have led to a better understanding of how human beings interpret audible warning

signals presented in their daily environments (Edworthy, Loxley & Dennis, 1991; Edworthy &

Adams, 1996). Design criteria for audible warning signals have been proposed for the purpose

of improving their appropriateness and suitability which will ultimately govern whether a set of

warnings are actually effective (Edworthy & Stanton, 1995; Edworthy & Adams, 1996). The

aforementioned authors believe it is essential to consider two vital elements. First, when an

audible signal is perceived, it must be recognized as a warning signal. Second, the signal’s

significance, and ideally, the response expected, must also be understood.

In order to ensure the recognition of audible warning signals, many researchers have

proposed design criteria to standardize their intensity, spectral content, length, temporal aspects

etc. (Edworthy, Loxley and Dennis, 1991, Patterson, 1982; Tran Quoc et Hétu, 1996;

Momtahan, 1990). An international standard (ISO 7731, 1986) is currently available for audible

warning signals in the workplace. The international standard for evacuation signal (ISO 8201,

1987), commonly referred to as the T-3, also addresses some of the acoustic parameters

necessary to ensure the recognition of this type of signal. It does not, however, specify the

signal’s spectral content. It exclusively addresses the signal’s length, sound pressure level and

temporal aspects.

The ISO 8201 standard stems from the works of the National Academy of Sciences,

Committee on Hearing, Bioacoustics, and Biomechanics (CHABA, 1975). The members were

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set the objective of suggesting an audible evacuation signal that would be, ”specific and simple

so that it would be universally recognized and easily distinguished from other alarm signals”.

Two specific considerations guided their choice of audible signal. First, the signal had to be

evident and easily perceived by the occupants of a building. In fact, the signal had to be

detectable in any ambient noise. The second consideration was that the distinctive

characteristics of the signal had to make the signal clearly different from a variety of other alarm

signals. It was important to limit the amount of confusion occupants felt when the alarm

sounded. The evacuation alarm must be instantly recognizable.

Acknowledging that the alarm would be activated in a variety of environments, where the

level and spectral content of the ambient noise could vary tremendously, the members of the

committee opted for a standard that addressed the temporal aspects of the signal, as opposed

to one that addressed its spectral content. According to the members, this approach has the

following advantages. First, the signal could be designed for any environment by matching the

signal to the existing background noise to optimize its perception. Second, having specific

temporal characteristics would avoid any confusion of the signal with other audible warning

signals, particularly those used outside. Third, the distinct temporal pattern allowed for easy

adaptation of the signal to sight and touch alarms. Finally, the problems surrounding the

adaptation of existing evacuation alarm systems to this temporal signal are minimized because

it is much easier to install a temporal switch into the current circuitry then it is to replace the

entire system with new signals. Consequently, the time and money involved in updating

existing systems with the temporal signal would be limited.

The temporal characteristics proposed by the CHABA committee differ somewhat from

that of the ISO 8201 standard but they are closely related. Nonetheless, it was the committee’s

belief that the audible signal would undoubtedly be recognized by its temporal characteristics. It

is questionable, however, whether the temporal characteristics proposed are sufficient enough

to exclusively guarantee the association of the alarm to a specific meaning and adequate

response, assuming a well-adjusted intensity level.

In general, the concepts of perceived hazard and auditory affordance are referred to by

the same studies that address the significance and the adequate response to audible signals

(Edworthy & Stanton, 1995; Stanton & Edworthy, 1998; Hellier, Wright & Edworthy, 2000). It is

evident that a warning signal should not only communicate the presence of a danger, but also

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the level of hazard related to that danger. When warning signals vary in their level of urgency

and are adequately associated with the level of danger involved in a situation, they gain a

behavioural advantage (Haas & Casali, 1995; Finley & Cohen, 1991). This process, referred to

as “hazard matching”, is the object of the recommendations that are made for implementation of

warning signals (Edworthy & Adams, 1996; Hellier, Edworthy & Dennis, 1995; Edworthy, Loxley

& Dennis, 1991; Momtahan & Tansley, 1989). It is known, for example, that the fundamental

frequency, harmonic series, amplitude envelope shape, delayed harmonics, speed, rhythm,

pitch range, and melodic structure all have clear and consistent effects on perceived urgency. A

signal’s perceived urgency is therefore related to several acoustic parameters.

Nonetheless, an individual’s interpretation of a warning signal cannot be limited to

acoustic parameters. There is also the associative meaning dimension that comes into play.

Gibson (1979) claimed that people do not solely attend to the purely physical aspects of objects

in the world; rather, we seek to interpret their meaning. This very theory is what brought

Stanton & Edworthy (1998) to propose the theory of auditory affordances. They argued that an

auditory warning is perceived in terms of its potential for action. They upheld their theory by

means of 4 main propositions: 1) we are surrounded by sounds; 2) we are introduced to sounds;

3) we learn sounds through seeing other people respond to them; and 4) sounds have a definite

function.

With fire alarms as an example, Edworthy and Stanton (1995) tried to explain this

concept. The audible signal associated with a fire alarm can be anything from a bell to a siren,

neither extremes having any direct relationship with the sound produced by an actual fire.

However, for most people, these signals have been the object of a learned association. Would

it be better to use a sound that produces an image of burning flames? It would seem that a

signal’s suitability is a function of its association to the fire and its ability to incite individuals to

move away from the source of danger. Consequently, it appears that certain situations would

be more appropriately signalled by an audible warning signal that has a significant acoustic

relation to the situation, a representational sound, while other situations will be better

represented by sound that has a learned association.

In their 1998 study in an intensive treatment unit (ITU), Stanton & Edworthy proposed

two hypotheses: A) the function of representative, environmental sounds will be identified more

readily than abstract, non-representative sounds, and; B) the interpretation of the function of a

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sound will be dependant upon the experience of the individual. The study was comprised of two

participant groups, ITU staff and non-ITU staff. The signals used throughout the study were

either signals typically used in the ITU (abstract sounds) or new signals designed to be

acoustically related to the meaning of each sound signal; in other words sounds that were

representational. For example, representational signals included CD recordings of a heart beat

for an EEG monitor, a nursery chime for an infant warmer, and bubbles for the syringe pump.

Preliminary results revealed difficulties in recognition of audible signals as well as poor

performances with abstract sounds, particularly during initial performances. To learn the

significance of abstract sounds requires considerable effort, whereas representational sounds

are more intuitive. Moreover, the authors noted an interaction between the type of signal and

the experience. In fact, hypothesis A) arguing that individuals would better identify

representative sounds, was verified for the group of participants that were unfamiliar with the

typical ITU audible signals, but was not retained for the individuals used to ITU warning signals.

The ITU staff showed a significantly superior success rate for the recognition of typical ITU

sound signals, whereas non-ITU staff were significantly better in the identification of the new

representative sound signals. The authors consequently proposed that the targeted population

be involved in the design of warning signals. Moreover, the theory of auditory affordances

suggests that individuals comprehend the sounds that surround them in terms of potential for

action. This implies that it is people’s physical reaction to the alarms that must be considered,

rather than what the alarms’ equipment is monitoring. According to the authors, this outcome is

subtle, but substantial in the design of new audible warning signals. The referents are the

actions required by people. In conclusion, the authors insisted that the development of new

audible signals would most likely rely on a combination of traditional and representational

warning signals.

Thus, based on the literature, it can be predicted that individuals having to recognize a

new audible signal, such as the T-3, will perform poorly according to the hypothesis that these

individuals will not have learned the significance associated with the signal prior to their

exposure. This hypothesis is further substantiated by the acoustic characteristics advocated by

the ISO 8210 standard, which convey little information related to a fire or an evacuation.

3.0 RESEARCH OBJECTIVESThis research project endeavours to answer three fundamental questions about the T-3

signal. These questions are associated with recollection, identification and urgency.

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The first objective of this project is to assess whether people can recall the T-3 signal. It is

essential to know if people believe that they have previously heard the T-3 to ascertain their

previous exposure to the signal.

The second objective is to evaluate if people can correctly identify the meaning of the

signal. It is one thing to say that you have heard a signal before, and something entirely

different to correctly identify the meaning of that signal.

The third objective is to measure the degree of urgency that people associate with the T-3.

Building occupants may not be able to identify the T-3 or they may not have even been exposed

to the signal previously. It is expected, however, that if they attach a high level of urgency to the

signal they will feel compelled to act on it if they unexpectedly hear it in a public building. The

perceived urgency is particularly important to assess whether the signal will prompt action in a

fire situation where no other occupants or fire cues are there to indicate a fire situation.

Two hypotheses have been developed to study the effectiveness of the T-3. The first

hypothesis is that the recollection of the T-3 will be lower than other warning signals. The

second hypothesis is that the identification of the T-3 would be lower than that of other signals.

This is because there are a limited number of buildings equipped with the T-3 and the potential

for the public to have been exposed to the signal is limited. Finally, no specific hypothesis was

formed regarding the perceived urgency of the T-3 signal.

4.0 METHODOLOGYTo investigate the recollection, identification, and perceived urgency of the T-3 an

experimental study was conducted. Early in the study it was determined that it would be

impractical to activate the T-3 in a number of public buildings to observe occupant’s response.

Instead, it was considered more appropriate to approach a sample of individuals and conduct

interviews in the field to obtain the data that would answer the study objectives.

4.1 ParticipantsA sample of participants, representative of the Canadian population in terms of gender

and age distribution, was approached in the field. It is a recognized methodology when

evaluating auditory warning signals to focus on the real users, measuring their capacity to make

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an association between sound and meaning (Edworthy & Stanton, 1995). The general public

constitutes the real users of the T-3 and it is essential that the research and subsequent

development of the T-3 be based on actual building occupants.

People were approached in public buildings such as shopping centers, libraries, and

airports. All of the buildings were places where the T-3 signal could be heard if the fire alarm

system had been installed or upgraded in the last few years.

4.2 Signals Tested

Although the objective of this project was to study the T-3, it was decided to test it among

5 other warning signals. It would have been an acceptable methodology to go around and test

only theT-3 without any other signal. This approach would however necessitate, meeting with a

large group of people to test the T-3 then to use another signal and test it with another group of

people to compare the recollection, identification and perceived urgency between the two

groups. This strategy was not used for fear of finding large discrepancies between groups

which could have been difficult to interpret if not enough was known about the participants

experience, background, prior exposure, etc. There was also the worry that exposing a person

to the T-3 “out of the blue” could be such a surprise to the participant that a large number of

wrong answers would be obtained which might not be representative of the “true” recollection,

identification and perceived urgency of the T-3.

It was decided to use a total of 6 signals which seems sufficient for the participants to

understand the context of the task while keeping the whole test under 5 minutes for each

participant. Experience in previous field studies in public buildings suggests that 5 minutes is

the maximum time you could expect participants to be prepared to answer questions. To

consider a case, it was necessary that the whole test be completed, therefore it was important

to ensure that participants would not give up before the end.

The signals selected were also used to validate the task. It was expected that the Car

Horn should obtain an overall good recollection and identification from the participants.

Consequently, if the findings would show a large number of participants not accurately

recollecting or identifying the Car Horn, that would indicate that the task was not well

understood by participants or the methodology not appropriate for the research objectives.

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The 6 signals selected were all warning signals. The signal selection was carefully made

to include signals that were expected to obtain a range of recollection and identification from

very good such as for the Car Horn or the Alarm bell and very poor performance such as for the

industrial Buzzer. It was expected that the T-3 would perform within that range. It was also

interesting to compare the performance of the T-3 with two other fire alarm signals: the Slow

Whoop which has many advocates in the United States and the alarm Bell which is used

extensively in institutional buildings in Canada.

Three CDs were prepared which presented six signals in different orders. The T-3 signal

was presented first, third and last among five other signals. The exact presentation order of the

signals on each CD can be seen in Table 1. To limit the number of CDs, and simplify the

analysis, it is considered acceptable in the warning literature to restrict the number of

presentation orders (Momtahan et al. 1993).

Table 1: Signal Presentation Order on Each CD

CD Signals Order

1 T-3 Car Horn Reverse Slow Whoop Buzzer Bell

2 Slow Whoop Car Horn T-3 Bell Reverse Buzzer

3 Bell Car Horn Buzzer Reverse Slow Whoop T-3

The signals were presented in different orders on each CD so that order effects could be

counterbalanced. Presenting one signal before another could affect the opinion a participant

would have had about following signals. For instance, having heard the Bell first, and identifying

it as a fire alarm, participants later interpretation of the T-3 signal may be coloured. By

changing the order of the signals so that the Bell is not always heard before the T-3 signal, this

colouring can be accounted for. This is why the T-3 was presented first, third and last, to

determine whether hearing the signal “out of the blue” as the first signal would provide

comparable recollection, identification and degree of urgency as listening to the T-3 after

hearing other signals.

An analysis of the acoustic characteristics of each of the signals has been conducted in

order to document the main parameters, such as the spectra and temporal patterns. All signals

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had an overall duration of 12 seconds. The Car Horn had a fundamental frequency of 350 Hz

with harmonics up to 2 kHz. It was sounded few times during the 12-second interval. The Slow

Whoop is characterized by a frequency sweep between 875 and 4000 Hz, and each sweep

lasted approximately 2 seconds. The Buzzer had a wide spectrum between 500 Hz and more

than 8 kHz. The Reverse alarm was an intermittent signal with a 400 msec ON period followed

by a 350 msec OFF period. The fundamental frequency was 1302 Hz with harmonics

significantly lower in level. The Bell is composed of three main frequencies (1244, 1866 and

2527 Hz). The T-3 is a 500 msec ON-500 msec OFF signal repeated three times followed by

an OFF period of 1.5 second. The fundamental frequency is 505 Hz with the odd harmonics

(3rd, 5th, 7th, etc.). The T-3 used in the study was recorded from Simplex 1996, 4100 Fire Alarm

Audio Demonstration CD. Appendix 1, at the end of this report, shows the spectrum analysis of

the 6 signals.

4.3 Materials

The signals were recorded so that they played at a maximum of 90 dBA when the CD

player was at maximum volume. This volume level is not considered harmful to the hearing of

the participant if the duration of the exposure is limited to 15 minutes or less and is not repeated

day after day over a long period of time (WHO, 1999). The interviewer adjusted the volume of

the CD player to a comfortable level for the environment they were in at the time of the study

before beginning the test (this volume was usually at 4 out of a maximum volume of 10). Each

participant, however, had the opportunity to adjust the volume during a 10-second period of

music, prior to listening to the test signals.

The signals were played on a CD Walkman (Sony Sports model D-SJ01) and both the

experimenter and participant had a set of headphones to listen to the signals (the experimenter

had Sony MDR-GO51 headphones). The participant listened to the signals through Sony Noise

Cancelling headphones (Sony MDR-NC20) so that the ambient noise of the environment did not

overly interfere with the quality of the test signals.

Three experimenters collected the data. All experimenters followed a rehearsed script so

that the participants experienced a similar situation with each experimenter. The experimenters

recorded the participants’ answers on a data sheet that the participant could view at the time of

the survey.

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The answers to the perceived urgency rating were recorded on a simple 1-10 scale,

although the psycho-acoustic literature lately suggests using a free-modulus magnitude

estimation scale or the cross modality matching (Hellier et al., 1995). It was decided that these

methods would not work well for the present study. These methods need to be explained very

carefully to participants before a study can begin, often taking long moments so that there is no

confusion, therefore the interviews would not have been under 5 minutes. Finally, the perceived

urgency rating was not the main objective of this study which was more concerned with

recognition. In our view, recognition of the T-3 could be better studied during a field study with a

large number of participants being involved for a short period of time. Consequently, the simple

1- 10 scale was used by participants to assess perceived urgency for the sake of simplicity

within the context of this field study.

4.4 Procedure

Initially, experimenters attempted to select participants as randomly as possible, however

under-represented groups were targeted near the end of the study so that a representative

sampling of the general Canadian population was possible. Participants were approached

when alone and inactive, resting or waiting for somebody on a bench or in the food court.

After an introduction, the experimenter asked the respondent if they were willing to

participate in a five-minute sound recognition study. Participants were told that they would listen

through headphones to six 12-second sounds that were being tested. It was explained that the

first sound, which was a music sample, was not part of the study, it was being played only to

check that the equipment was working and that the sound level was comfortable. The

participants were then told that after this music sample, the six test sounds would be played and

after each sound, the CD player would be stopped so that they could be asked three questions.

The questions were stated at this point so that the respondents would know exactly what they

would be asked.

The questions were “Have you heard this sound before?” “What do you think this sound

means?” and finally, “How urgent do you feel this sound is on a scale from 1 to 10? 1 being not

urgent at all and 10 extremely urgent.” The first question tested the recollection of the signal,

the second tested the ability to correctly identify the signal and the last question rated the

perceived urgency of the signal.

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It was heavily emphasized that the sounds heard on the CD were from in and around

large buildings, such as the one they were in at the time of the interview.

After the participant had listened and responded to each of the signals, they were asked

for their age and occupation. These characteristics were only obtained to explain individual

differences during analysis, not to discriminate against the participation of any person or groups

of people. When all of the data had been collected, the participants were carefully debriefed.

The experimenters explained that the study was on the recollection and identification of fire

alarm signals and that the T-3 signal was the new evacuation signal to be installed in public

buildings.

5.0 STUDY RESULTSThe raw data from this study was entered into SPSS 6.0 so that a statistical analysis could

be performed. Nominal and ordinal data were collected during the study and nonparametric

tests were used in the analysis. Nonparametric tests were selected because they are more

robust and better suited to deal with nominal and ordinal data. The results, therefore, were

achieved through the use of such tests as the Sign test, the Kruskal-Wallis one-way analysis of

variance, and the Wilcox matched pairs signed-ranks test. For the purpose of the analysis, an

alpha level of .05 was used as the critical value for determining a significant difference.

Therefore, if p was less then 0.05 (p < .05) the results were considered significant.

5.1 Respondent ProfileThe sample contained 307 participants ranging in age from 15 to 85 years old

(mean = 38.45, SD = 17.22). The majority of the respondents were recruited from in and

around shopping centers and public buildings in the Ottawa area. The rest were recruited at the

Ottawa International Airport. The age distribution of the sample was similar to the age

distribution of Canada, as reported by Statistics Canada (2000), see Table 2 below.

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Table 2: Population Distribution of Canada and the Study Sample

Age Group Canada Study Sample0-14 19% 0%

15-19 7% 15%

20-29 14% 23%

30-49 32% 34%

50-64 16% 20%

65- 85 11% 8%

86 and over 1% 0%

As Figure 1 shows, there was a higher number of young women sampled. It is speculated

that this occurred because young woman may frequent the malls, where many of the interviews

took place, more often than other age or gender groups.

Figure 1: Gender and Age Distribution of the Study Sample

The total sample contained 164 women (53%) and 143 men (47%). According to Statistics

Canada (2000), the Canadian population is also slightly biased towards women (50.5%

Females and 49.5% Males). The sample was composed of 173 people who worked in large

buildings (56%), 69 students (22%), 45 people who were unemployed at that time (15%), and

20 people who worked outside or in small buildings (7%).

0102030405060

15-19 20-29 30-49 50-64 65-85

Age

Freq

uenc

y

FemalesMales

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5.2 Merging Data from the Three CDsThe three CDs that were used to gather data were designed to present the signals in

three different orders so that if an order effect occurred, it could be taken into account during the

analysis. Consequently, the T-3 was presented as the first signal to one third of the sample, as

the third signal to another third of the sample, and as the last signal to the last third of the

sample. In total, 101 participants listened to CD1 and 103 listened to CD2 and CD3 for a grand

total of 307 participants in the study.

There were significant differences between the three CDs for the T-3 in recollection

x2(2,307)=9.87, p < .01, and urgency x2(2,307)=11.14, p < 0.01. Both of these statistics were

computed using the Kruskal-Wallis one-way analysis of variance. As presented in Table 3, CD3

where the T-3 was presented last was the one that obtained the higher recollection and

urgency. Interestingly, there were no significant differences found in recollection or urgency for

the alarm Bell, which was placed in the first, fourth and last positions, x2 (2, 307)= 1.9242,

p<.05.

Table 3: Results to the T-3 Signal for Each CD

CD Presentationlocation of the T-3

Recollection% of “Yes”

Identification% of correct answer

PerceivedUrgency rating

1 1st signal on CD 59.4% 3.0% 3.47

2 3rd signal on CD 73.1% 5.8% 3.80

3 6th signal on CD 78.6% 7.8% 4.64

An order effect was discounted because biasing did not occur with the Bell. Also,

basically only one experimenter used each CD during the experiment, and so the difference in

response could be as dependent on the experimenter as the signal order presentation. In fact,

it is believed that the difference in perceived urgency of the T-3 occurred because of a

procedural difference between experimenters. For example, when a subject hesitated between

two urgency ratings, the experimenters prompted the participant differently for a definite

response. One experimenter had a tendency to systematically prompt for a higher rating.

When the participant hesitated between “a 3 or a 4”, the experimenter would say, “so that would

be a 4?” while the other two experimenters did not prompt the participant. This is believed to be

why a significant difference in urgency for the T-3 occurred between experimenters when a

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Kruskal-Wallis one-way analysis of variance was performed, x2(2,307)=7.05, p < .05 . Despite

the biasing, the shape of the distribution remained the same for each experimenter. For this

reason, the procedural difference between the experimenters was ignored for the purpose of

analysis.

All of the participants who were interviewed were used in the analysis: no cases were

discarded. Of the ten respondents who failed to recall the Car Horn, the original manipulation

check, six were over 50 years old. Apart from failing to recall the Car Horn, their other

responses were not overly different from the responses of the average participant, so their

cases were kept in the final analysis.

5.3 Signal Recollection

The first question participants were asked after listening to each signal was “Have you

heard this signal before?” The answer to this question on recognition was either “yes” or “no”.

Table 4 presents the number of positive answers to each of the signals.

Table 4: Number of Occupants who Confirmed Having Heard a Signal Before

Signal Participants (N=307) PercentageCar Horn 297 97%

Reverse alarm 280 91%

Buzzer 249 81%

T-3 219 71%

Bell 177 58%

Slow Whoop 159 52%

There was an overall significant difference found between how often participants recalled

each of the signals, Q(5, 307)=28.15, p< .001. This statistic was computed using the

Cochran Q test which is used when looking for significant differences between three or more

matched sets of frequencies or proportions. The Car Horn was recalled the most often, by 297

out of 307 participants (97%), followed by the Reverse alarm, which was recalled by 280 people

(91%). The Buzzer was recalled by 249 people (81%), the T-3 by 219 people (71%), the Bell by

177 people (58%). Finally the Slow Whoop was recalled by 159 people (52%). Participants

were significantly more likely to say that they had heard the T-3 then the Slow Whoop, x2 (1,

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307)= 27.80, p < .001 and significantly more likely to say that they had heard the T-3 then the

Bell, x2(1, 307)= 13.91, p< .001. Participants who said they had heard a signal before, however,

could not necessarily identify the signal correctly. Figure 2 below shows the percentage of ‘yes’

answers compared to ‘no’ answers.

Figure 2: Recall Percentage of each Signal

5.4 Signal Identification

The second question that the participants were asked was if they knew what the signal

meant. In many cases the subject, although asked, “what does this sound mean”, gave

responses that would have been expected had they been asked, “what is this sound”. For the

purpose of analysis the answers were placed into three simple categories, “right”, “wrong” and

“I don’t know”. The definition of “right” used for the T-3, Slow Whoop and Bell, all of which were

fire alarms, was that the answer had to be related to fire alarms or evacuation to be considered

“right”. Answers given in response to the industrial Buzzer were defined as “right” if they were

related to a factory or mechanical setting, although it is possible that participants could have

heard this signal in a different context. The Reverse alarm was operationally defined as correct

if the participant identified it as a Reverse alarm. The answers “snow removal” and “garbage

truck” were also accepted because in such situations the signal could be heard as the vehicle

reverses. The Car Horn was considered correct when participants identified it as a horn. The

answers accepted as correct for this signal, included car horn, car alarm, truck horn and boat

horn.

0102030405060708090

100

T3 CarHorn

Reverse SlowWhoop

Buzzer Bell

Signals

yes no

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Table 5 presents the number of occupants who correctly identified the different signals.

The T-3 was identified correctly only 6% of the time (17 out of 307 said it was a fire alarm). The

Car Horn was identified correctly 98% of the time (302 people identified it correctly), the

Reverse alarm was correctly identified 71% of the time (by 218 people), the Slow Whoop 23%

of the time (by 71 people), the Buzzer 2% of the time (6 people) and the Bell 50% of the time

(by 155 people).

Table 5: Number of Occupants who Correctly Identified Each Signal

Signal Participants (N=307) PercentageCar Horn 302 98%

Reverse alarm 218 71%

Bell 155 50%

Slow Whoop 71 23%

T-3 17 6%

Buzzer 6 2%

The seventeen people who correctly identified the T-3 as a fire or evacuation alarm were

aged 21 through 84 years old (M = 41.20, SD = 16.52), and were equally likely to have been

male or female (53% female and 47% male). Among these seventeen participants there was,

for example, a mechanic, a student, a janitor, an accountant, a person who was looking for work

at the time, and a Ph.D. fellow.

There is a very significant difference between how often each of the signals was correctly

identified, x2(5, 307)=555.52, p < 0.001. The T-3 was identified correctly less often than any

other fire alarm signal (Bell and Slow Whoop). Figure 3 gives a visual representation of these

findings.

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Figure 3: Percentage of Signals Identified

It is also interesting to notice that about the same proportion of participants answered that

they “didn’t know” the three fire alarm signals (T-3, Slow Whoop and Bell). For the T-3, 69 of

307 or 22% of the participants said they could not identify the sound, for the Slow Whoop, 64 of

307 participants or 21%, and for the Bell, 70 of 307 people or 23% said they didn’t know the

signal. Eight participants in the sample (3%) could not identify any of the fire alarm signals.

5.5 Signal Recollection and IdentificationIt is informative to know how often participants could correctly identify a signal after stating

that they “had heard the signal before”. Although the T-3 was identified correctly by 6% of the

population, only 4% of the participants said that they had heard the T-3 before and then

identified it as a fire alarm. Participants who said that they recalled the T-3 but then went on to

state that they could not identify the signal accounted for 10% of the population. An astounding

57% of the participants felt that they recalled the T-3 but then erroneously decided that the

signal was something other than a fire alarm. Five participants (2% of the total population)

correctly identified the T-3 as a fire alarm but did not state that they had heard the T-3 first. It is

assumed that they “guessed” the right answer. Three of them were male, two were female and

they ranged in age from 16 to 59 years old (M= 33.20, SD= 16.08). These results are displayed

in Figure 4.

0

10

20

30

40

50

60

70

80

90

100

T3 Car Horn Reverse SlowWhoop

Buzzer Bell

Signal

Perc

enta

ge RightWrongDon't know

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Figure 4: Recollection and Identification of the Temporal-Three

As can be seen in Figure 5, the Car Horn was recalled and identified correctly 96% of the

time whereas the T-3 was recalled and identified correctly only 4% of the time. The Reverse

alarm was recalled and identified correctly 69% of the time, the Slow Whoop 14%, the Buzzer

1%, and the Bell 38% of the time.

Figure 5: Percent of Each Signal Recalled and Identified Correctly

0

10

20

30

40

50

60

70

80

90

100

T3 Car horn

Reverse

Slow Whoop

Buzzer

Bell

Signal

Perc

ent

4%

57%

2%

15%

10%

12%

4% Yes, recall it, right answ er

57% Yes, recall it, w rong answ er

2% No, do not recall it, right answ er

15% No, do not recall it, w rong answ er

10% Yes recall, don't know

12% No, do not recall it, don't know

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When the T-3 was identified as something other than a fire alarm, 61% of the time it was

because the participants imagined the signal in the context of a domestic environment instead

of a public building. This occurred despite the conscious attempt by all experimenters to

carefully state that all of the signals heard on the CD were from in and around large buildings.

As presented in Table 6, most often the T-3 was identified as a signal related to the telephone

with answers that included busy signal, telephone, phone that is on hold and answering

machine.

Table 6: Wrong Identification of the Temporal-Three

Identification Participants (N=174) PercentageBusy phone signal 55 32%

Phone beep 20 12%

PA pre-announcement 18 10%

Reverse alarm 17 10%

Time signal 14 8%

Alarm clock 13 7%

TV message coming 10 6%

Hospital alarm 6 3%

Bank machine 4 2%

Other identification 17 11%

The Car Horn was perceived correctly to be a horn for a vehicle by almost all of the

participants (98%). Five people gave odd answers that included, reverse and pool horn. The

Reverse alarm was identified correctly by the majority of respondents (71%). Wrong answers

were generally associated with a domestic environment and included busy phone signal, time

signal and alarm clock (39%). The Slow Whoop was correctly identified as a fire alarm by 23%

of the sample. Among the wrong answers were emergency vehicle or siren (62%) bomb

warning (14%) and security alarms (6%). The industrial Buzzer was incorrectly identified as part

of a domestic environment 50% of the time. Wrong answers in this case included alarm clock,

stove timer, and door buzzer. The Bell was perceived as a fire alarm by half of the participants.

Wrong answers included security alarm (6%), radios and alarm clock (6%), and train sounds

(3%).

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5.6 Signal Perceived Urgency

Each participant was asked to rate, on an ordinal scale from 1 to 10, the degree of

urgency they felt for each signal, one was not at all urgent and 10 meant they felt the signal was

extremely urgent. The differences in perceived urgency between all of the signals, were

significant, x2(5,307)= 311.87, p< .001.

Table 7: Difference in Perceived Urgency between T-3 and Other Signals

Signal PerceivedUrgency

StandardDeviation

Probability

T-3 3.97 2.42

Buzzer 4.91 2.74 p< .001

Car Horn 4.93 2.46 p< .001

Reverse 5.60 2.78 p< .001

Slow Whoop 6.01 2.50 p< .001

Bell 7.17 2.74 p< .001

As can be seen in Table 7, the T-3 was considered the least urgent of all the signals.

When the T-3 was compared to each of the signals separately it was significantly less urgent

than each of them. The T-3 received an overall rating of 3.97, which could be assessed as a

low urgency rating on a scale from 1 to 10. The Buzzer, Car Horn and Reverse signal all

received urgency ratings between 4.91 and 5.60, which could be judged as medium urgency

ratings. Finally the Slow Whoop and Bell received ratings of receptively 6.01 and 7.17, which

could both be considered high urgency ratings.

On each of the three CDs one of the alarm signals was played first. Although in the initial

analysis an order effect was discounted, it was considered prudent to analyze the average

perceived urgency of each of these signals when they were played first. The T-3, when no

other signal had been heard beforehand, had a mean perceived urgency rating of 3.58, the

Slow Whoop had an urgency rating of 6.40 and the Bell had an urgency rating of 7.13. In other

words they remained unchanged, which further confirmed the lack of an order effect caused by

signal presentation.

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5.7 Signal Identification and Perceived Urgency

It is interesting to consider the urgency rating of each signal while keeping in mind the

identity of the signal given by participants. When any of the signals were identified as fire

alarms, independent of whether or not they actually were, the urgency generally increased as

can be seen in Table 8. Only the Car Horn was never identified as a fire alarm so this signal is

not included in Table 8.

Table 8: Identification of any Signal as a Fire Alarm and Perceived Urgency

Signal # of Ss whodid not

identify thesignal as afire alarm

Urgencywhen not afire alarm

# of SS whoidentified

signal as afire alarm

Urgency as afire alarm

Significance

T-3 290 3.83 17 6.29 p<0.001

Slow Whoop 236 6.76 71 7.42 p<0.05

Buzzer 265 4.49 42 7.55 p<0.001

Bell 152 5.89 155 8.43 p<0.001

Reverse 298 5.59 9 5.67 N.S. (p=.88)

The average urgency rating changed from 3.83 to 6.29 when participants identified the T-

3 as a fire alarm signal. The same tendency was observed for the Slow Whoop, the Buzzer and

the Bell which obtained significantly higher urgency ratings when identified as fire alarms.

There was no significant difference for the Revere alarm although results are in the same

direction.

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6. 0 CONCLUSIONS

The objectives of this research project were to evaluate if the T-3 signal was an alarm

signal that the general public could recall and identify. Another objective of this study was to

assess the level of urgency people would attach to the T-3 signal.

Among the signals tested, the Car Horn was recalled the most frequently, followed by the

Reverse signal, the Buzzer, the T-3, the Bell, and finally the Slow Whoop. This order of

recollection, however, proved inconsequential. Often participants recalled the T-3 as something

other than a fire alarm: usually the T-3 was identified as an everyday household signal, such as

a busy telephone signal.

It was found that only 6% of the population surveyed was able to identify the T-3 as a fire

alarm signal. When compared to the Slow Whoop, which was identified as a fire alarm by 23%

of the population, and the Bell, which was identified correctly by 50% of the population, it

becomes obvious that the T-3 is not a well known fire alarm.

It is possible that the procedure used led to the problem of incorrect identification.

Although people were briefed that the signals they were going to hear through the headphones

were from in and around buildings like the one they were in, a considerable number of

participants identified signals as sounds that could be found in domestic or small scale

environments. Since participants were using headphones they may have had difficulty

transferring the unfamiliar signals to the actual surroundings. However, this was not the case

with more familiar signals such as the Car Horn and the Reverse alarm which obtained correct

identification (98% and 71%) when heard through headphones.

Regarding perceived urgency, the T-3 was considered to be the least urgent signal among

all six of the signals tested. The T-3 scored a mean of 3.97 on a scale of 1 to 10 with 10

indicating extreme urgency. In contrast, the Bell scored the highest urgency rating with a mean

of 7.17, on the same scale.

Generally when a signal was identified as a fire alarm the perceived urgency was

significantly increased. This finding applies also to the T-3. It is suggested, therefore, that to

increase the perceived urgency of the T-3, the public should be educated to readily identify the

sound pattern of the T-3 as a fire alarm signal. In light of the temporal characteristics of the T-3

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signal, it is not surprising to obtain a weak degree of perceived urgency associated to the signal.

In fact, the T-3 ’s rhythm does not seem of sufficient speed to convey an adequate degree of

urgency for an evacuation. It is unlikely, however that the T-3 will be modified since it is an ISO

standard and is now a requirement in building codes in Canada and the USA. Consequently,

the acquisition of the T-3’s significance and expected response will depend highly on educating

the public to ensure that the T-3 improves life safety.

7.0 RECOMMENDATIONS

There are a number of approaches that can be considered to educating the public about

the recollection, identification and behaviour that they are expected to perform upon hearing the

T-3. One possibility is to broadcast an advertisement campaign on television or radio. Although

this method would reach the greatest number of people, and could have effective content, such

advertisements are extremely costly. Another strategy would be to distribute leaflets and

brochures. This is a less costly alternative, but it might be difficult to graphically display the

sound of the T-3 signal and ensure that the general public will make the connection between a

graphic display and the auditory signal. An interesting suggestion, made by a member of the

fire alarm industry, would be to display the T-3 signal on the Internet which seems to be a new

means by which an increasing number of people learn new things. Another good idea could be

to make the new evacuation signal the theme for the National Fire Safety week, with the sound

being played by the media who cover the events around Canada and the United States.

Another alternative may be to educate the public while they are visiting buildings by

performing evacuation drills. After the fire alarm is activated, a recorded message would be

played stating: “This is the evacuation signal, please leave the building immediately”. One

drawback of this approach is that this would only be possible in buildings equipped with voice

communication capabilities. Further, these kinds of recorded messages are not very informative

and may not prompt overall evacuation movement. Moreover, this approach is unlikely to

educate the public rapidly because the potential of exposing the general public to such a drill or

alarm activation is limited.

A more promising approach would be to require immediate alarm signal upgrading in all

elementary and high schools. The majority of the population learns fire safety during schooling

years. The lessons learned at this time are applied for the rest of life. Children would rapidly

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learn the sound pattern of the T-3 and would be taught the associated meaning and behaviour,

which they would be able to transfer to other buildings that they would be visiting in the future.

In an effort to educate the public so that they can identify the T-3, the USA has decided to

make all single station smoke alarms, also commonly referred to as, “home smoke detectors”

sound the T-3. Canada has decided to go against this practice because the T-3 signal is

specifically the evacuation signal that is supposed to unequivocally mean, “evacuate the

building immediately.” This is not the common behaviour observed when the smoke alarm

sounds in a person’s apartment or house. Within a dwelling, upon hearing the smoke alarm,

unless substantial fire cues are present, occupants usually investigate the situation in order to

decide on the best course of action. Since most smoke alarm activations in dwellings are due to

non-fire-related problems or minor incidents that can be efficiently controlled by the occupant,

the best response to the smoke alarm is not to “immediately evacuate”. Canadians have a

strong logical rational for their decision requiring that smoke alarms should not sound the T-3

signal. However, it has been demonstrated that it is extremely difficult to attach a behavioural

response to a warning signal (Stanton & Edworthy, 1998) and therefore it is unlikely that people

will evacuate upon hearing the T-3 from a smoke alarm in American homes. In fact, the

American approach has the advantage of exposing a large number of occupants to the T-3

signal since smoke alarms have a high probability of activation. Consequently, the American

public is more likely to be able to recall and identify the T-3, which is not a guarantee that

people will evacuate upon hearing the signal, but does mean that they will most likely correctly

identify the signal. It would be interesting to conduct the signal recollection study in the USA to

assess if the recollection and identification of the T-3 is superior to the results of the Canadian

study, since smoke alarms sold for the last 3-4 years in the USA all sound the T-3.

As already stated, the T-3 was originally intended in the ISO standard 8201 (1987) to be

used as the “International Emergency Evacuation Signal”. Despite this, it is often installed in

buildings as the fire alarm signal. According to the ISO definition, some public buildings should

not sound the T-3 if their Fire Safety Plan calls for occupants to stay-in-place or relocate in case

of a fire. It also means that the T-3, which is currently supposed to be the universal evacuation

signal, would be sounded for non-fire incidents such as for a bomb threat, chemical spill, gas

leak, nuclear radiation, etc. which require an evacuation of the building. From all the research

conducted in the field of human behaviour during building evacuation, it appears unrealistic to

expect that a signal such as the T- 3, by itself, could ever instigate a complete building

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evacuation of all occupants. The results of this study certainly dispute the suggestion that the

temporal content of the T-3 may be sufficiently urgent enough to trigger an evacuation response

as suggested by previous scientists (Edworthy et al. 1995; Haas & Casali, 1995). This

suggestion was also rejected in the 70’s when the T-3 was developed. A signal by itself cannot

convey a sufficient enough message of urgency to people that will let them know readily that

they are expected to evacuate a building.

The field of psycho-acoustic has, however, evolved tremendously. It is now known that

signals are built with a number of characteristics and these characteristics can greatly influence

the perception, interpretation and response of a person to that signal. For example, a high pitch

or high repetition rate will convey a higher degree of urgency then a signal with low pitch or a

low repetition rate. The representational characteristics of a signal are also an important factor.

Many occupants like the evacuation alarm that emits 120 pulses a minutes because it matches

very well the pace of a moving crowd down a stairwell. Even when the occupants can recall

and correctly identify a warning signal they do not necessarily comply with the expected

behaviour. Thus, it is not because people will recall the T-3 that they will necessarily evacuate a

building. They will still need more information to confirm the situation and obtain precision on

the expected evacuation movement.

Nevertheless, it is believed that the implementation of the T-3 is a step in the right

direction because building occupants need a standard fire alarm signal that they can

immediately identify when the fire alarm is activated. In fact, it is suggested that the T-3 should

be used regardless of the evacuation, or non-evacuation, strategy used in all public buildings in

order to limit the variety of signals that can be found in buildings. It is our recommendation that

all fire alarms and smoke alarms should sound the T-3, to improve people’s recollection and

identification of the signal. The response to the signal will still need to be learned, and most

likely will still need to be prompted by voice communication instructions or by the behaviour and

directions given by staff. It cannot be expected that occupants will immediately start evacuation

or relocation movement upon hearing the T-3 signal; more information will always be needed to

ensure occupant safe response during a fire incident in a public building.

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8.0 FUTURE WORK

This study is the very first attempt at looking at the occupant response toward the T-3.

Although this signal was developed over a long period of time, there was never any work to

study the efficiency of this signal with actual building occupants. The findings from this study

open up a large number of questions that should be researched.

The same test should be repeated with occupants of a building where the T-3 is the fire

alarm signal to verify if recognition is better in those occupancies. The T-3 is the signal used for

the fire alarm in a number of new or refurbished office buildings. In those buildings, occupants

should have been trained during an evacuation drill for example in the first few months of

occupation. It would be interesting to assess if occupants can recognized the T-3 after a one

time exposure to the signal during a fire drill, if they can transfer this recognition to other type of

environments and if they still recognize the T-3 when produce with different sounds.

Also the study could be repeated in the United States where smoke alarms emit the T-3 to

assess if this educational approach is indeed effective for signal recognition. In the States

where NFPA 72 is applied, houses in new neighbourhood should all be equipped with smoke

alarms sounding the T-3. Would these people recognize more readily the T-3 signal as a fire

alarm? Would they be able to transfer this knowledge to other type of occupancies? Do they

think they should evacuate when hearing the T-3 signal? These are very interesting questions

that should be studied.

A number of people who have reviewed this work have suggested that the T-3 used in this

study, which was an electronic sound, might explain the poor urgency rating obtained by the

signal. Many suggested that a study should be conducted to assess the difference in

recollection, identification and perceived urgency with the T-3 emitting the sound of the slow

whoop, the bell, buzzer or some other sounds.

Yet if it is planned to introduce a recorded message to inform the occupant that the

activated signal is the new alarm “evacuation” signal, what should be the content of the

message. Little is known at this time on what message content is most effective, what should

be the wording, should it be a male or a female voice, how many times should it be repeated,

etc.

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Much more work is necessary to better understand the impact of introducing the T-3 in

public buildings and how to ensure that occupants’ response matches the fire safety plan

expectations.

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9.0 REFERENCES

CHABA, 1975, “A proposed standard fire alarm signal”, Fire Journal, Vol. 69, No.4, pp. 24-27.

Edworthy, J., 1994, “ The design and implementation of non-verbal auditory warnings” AppliedErgonomics, Vol. 25, No. 4, pp. 202-210.

Edworthy, J. and Adams, A., 1996, Warning Design. A Research Prospective. Taylor &Francis, London, 219 p.

Edworthy, J., Hellier, E., Hards, R., 1995, “The semantic association of acoustic parameterscommonly used in the design of auditory information and warning signals”, Ergonomics, Vol.38, No. 11 pp. 2341-2361.

Edworthy, J., Loxley, S. and Dennis, I., 1991, “Improving Auditory Warning Design:Relationship between Warning Sound Parameters and Perceived Urgency”, Human Factors,Vol. 33, pp. 205-231.

Edworthy, J., Stanton, N., 1995, “A user-centered approach to the design and evaluation ofauditory warning signals: 1 Methodology”, Ergonomics, Vol. 38, No. 11, pp. 2262-2280.

Finley, G.A. & Cohen, A.J., 1991, “Perceived urgency and the anaesthetist : responses tocommon operating room monitor alarms”, Canadian Journal of Anaesthesia, Vol. 38, pp.958-964.

Gibson, J.J., 1979, The Ecological Approach to Visual Perception. Houghton-Mifflin, New York.

Haas, C. H., Casali, G. J., 1995, “Perceived urgency of and response time to multi-tone andfrequency-modulated warning signals in broadband noise”, Ergonomics, Vol. 38, No. 11, pp.2312-2326.

Hellier, E., Edworthy, J. & Dennis, I.,1995, “A comparison of different techniques for scalingperceived urgency”, Ergonomics, Vol. No. 38, pp.659-670.

Hellier, E., Wright, D.B. & Edworthy, J., 2000, “Investigating the perceived hazard of warningsignal words”, Risk Decision and Policy, Vol. 5,pp. 39-48.

ISO 7731, 1986, Danger signals for work places – Auditory danger signals. InternationalOrganization for Standardization, Geneva, Switzerland.

ISO 8201, 1987, Acoustics – Audible emergency evacuation signal. International Organizationfor Standardization, Geneva, Switzerland.

Karter, J. M., 1998, “Fire loss in the United States during 1997”, National Fire ProtectionAssociation, Internal report, Quincy, MA.

Laroche, C., Tran Quoc, H., Hétu, R., McDuff, S., 1991, “Detectsound: A computerised modelfor predicting the detectability of warning signals in noisy workplaces”, Applied Acoustics,Vol. 32, pp. 193-214.

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Mande, I., 1975, “A standard fire alarm signal temporal or ‘slow whoop’”, Fire Journal, Vol. 69,No.6, pp. 25-28.

Momtahan, K.L, Hétu, R., Tansley, B., 1993, “Audibility and identification of auditory alarms inthe operating room and intensive care unit”, Ergonomics, Vol. 36, No. 10, pp. 1159-1176.

Momtahan, K.L., 1990, Mapping of psychoacoustic parameters to the perceived urgency ofauditory warning signals, Unpublished Master’s thesis, University of Carleton, Ottawa,Ontario, Canada.

Momtaham, K.L & Tansley, B., 1989, “An ergonomic analysis of alarm signals in theoperating and recovery rooms”, Annual Conference of the Canadian AcousticalAssociation, Halifax, Nova Scotia, Canada.

National Academy of Sciences, Committee on Hearing, Bioacoustics, and Biomechanics,1974, A Proposed Standard Fire Alarm Signal. Office of Naval Research, Report ofWorking Group 73, Contract No. N00014-67-A-0244-0021, USA.

Patterson, R. D., 1982, Guidelines for auditory warning systems on civil aircraft, Civil AviationAuthority paper 82017.

Proulx, G., 1994, "The Time Delay to Start Evacuating Upon Hearing a Fire Alarm",Proceedings of the Human Factors and Ergonomics Society 38th Annual Meeting, Vol. 2,Human Factors and Ergonomics Society, Santa Monica, CA, pp. 811-815.

Proulx, G., Laroche, C., Latour, J.C., 1995, “Audibility problems with fire alarms in apartmentbuildings”, Proceeding of the Human Factors and Ergonomics Society 39th AnnualMeeting, Vol. 2, Human Factors and Ergonomics Society, Santa Monica, CA, pp. 989-993.

Stanton, N. & Edworthy, J., 1998, “Auditory affordances in the intensive treatment unit”,Applied Ergonomics, Vol. 29, pp. 389-394.

Statistics Canada, 2001 <http://www.statcan.ca/english/Pgdb/People/Population/demo31a.htm>

Tran Quoc, H. & Hétu, R., 1996, “La planification de la signalisation acoustique en milieuindustriel: critères de conception des avertisseurs sonores de danger”, Acoustiquecanadienne, Vol. 24, pp. 3-17.

Tong, D., Canter, D., 1985, “The decision to evacuate”, Fire Safety Journal, Vol. 9, no 3, pp.257-265.

WHO, 1999, “Community noise”, World Health Organization, Geneva.

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Appendix 1

Spectrum Analysis of the Signals Tested

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Car Horn

Slow Whoop

Buzzer

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Reverse alarm

Temporal-3

Bell