auditory, tactile, and vestibular systems

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Auditory, Tactile, Auditory, Tactile, and Vestibular and Vestibular Systems Systems Human Factors Psychology Human Factors Psychology Dr. Steve Dr. Steve

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Auditory, Tactile, and Vestibular Systems. Human Factors Psychology Dr. Steve. Pressure. Time. Properties of Sound. Sound is the vibration of air molecules Amplitude - sound pressure perceived as loudness Frequency - Cycles per second(Hertz) perceived as pitch - PowerPoint PPT Presentation

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Page 1: Auditory, Tactile, and Vestibular Systems

Auditory, Tactile, and Auditory, Tactile, and Vestibular SystemsVestibular SystemsHuman Factors PsychologyHuman Factors Psychology

Dr. SteveDr. Steve

Page 2: Auditory, Tactile, and Vestibular Systems

Properties of SoundProperties of SoundSound is the vibration of air moleculesAmplitude - sound pressure perceived as loudnessFrequency - Cycles per second(Hertz) perceived as pitchTimbre - quality of sound

Pre

ssur

e

Time

Which sound has the greatest amplitude?Which has the highest frequency?

Page 3: Auditory, Tactile, and Vestibular Systems

Decibel ScaleDecibel ScaleSourceSource Intensity Intensity # Times > # Times >

TOHTOHJet at take-off; ear damage Jet at take-off; ear damage

likelylikely140 dB140 dB 10101414

Threshold of painThreshold of pain 130 dB130 dB 10101313

Front row of a rock concertFront row of a rock concert 110 dB110 dB 10101111

Walkman at maximum volumeWalkman at maximum volume 100 dB100 dB 10101010

Vacuum cleanerVacuum cleaner 80 dB80 dB 101088

Busy streetBusy street 70 dB70 dB 101077

Normal conversationNormal conversation 60 dB60 dB 101066

Quiet officeQuiet office 40 dB40 dB 101044

WhisperWhisper 20 dB20 dB 101022

Normal breathingNormal breathing 10 dB10 dB 101011

Threshold of hearingThreshold of hearing 0 dB0 dB 101000

Sound intensity (dB) = 20 log (P1/P2); where P2 is the threshold of hearing

Page 4: Auditory, Tactile, and Vestibular Systems

Psychophysical Scaling of Psychophysical Scaling of SoundSound

1 sone = 40 dB tone of 1,000 Hz; Loudness doubles with each 10 dB increase

02468

1012141618

30 40 50 60 70 80Intensity of 1000 Hz tone (dB)

Loud

ness

(son

es)

Page 5: Auditory, Tactile, and Vestibular Systems

Equal Loudness CurvesEqual Loudness CurvesLoudness is affected by sound frequency. Humans are sensitive to sounds between 20 Hz and 20,000 Hz, but most sensitive to 1,000 - 4,000 Hz range. All tones along a contour are equally loud. 1 phon = perceived loudness of a 1 dB, 1000 Hz tone

100 Hz

500 Hz

1000 Hz

2000 Hz

5000 Hz

10000 Hz

20000 Hz

Page 6: Auditory, Tactile, and Vestibular Systems

Anatomy of the EarAnatomy of the Ear

Converts sound energy (outer ear) to mechanical energy (middle ear) to electrical nerve energy (inner ear), then sends signal to the brain

Page 7: Auditory, Tactile, and Vestibular Systems

CochleaCochlea

High frequencies ------------------------------------------------- Low frequencies

Page 8: Auditory, Tactile, and Vestibular Systems

Parts of the Ear ReviewParts of the Ear Review Pinna – Pinna – collects sound, helps localization (Holds up glasses)collects sound, helps localization (Holds up glasses) Tympanic Membrane (ear drum)– Tympanic Membrane (ear drum)– at end of at end of ear canalear canal, vibrates to , vibrates to

sound pressure (like a drum head)sound pressure (like a drum head) Ossicles – Ossicles – bones of middle ear that convert sound to mechanical bones of middle ear that convert sound to mechanical

energy. energy. – MalleusMalleus (hammer) (hammer) is the largest bone and receives vibration from ear is the largest bone and receives vibration from ear

drum, which then strikes thedrum, which then strikes the IncusIncus (anvil), (anvil), which is hinged to the which is hinged to the smallest bone, thesmallest bone, the StapesStapes (stirrups), (stirrups), which presses on the which presses on the Oval Oval WindowWindow of the cochlea. of the cochlea.

CochleaCochlea – “snail-like organ” where mechanical energy is – “snail-like organ” where mechanical energy is transduced to electrical nerve energy, by way transduced to electrical nerve energy, by way Hair Cells Hair Cells along the along the waving waving Basilar MembraneBasilar Membrane that “fire” when they are bent against that “fire” when they are bent against the rigid the rigid Tectorial MembraneTectorial Membrane of the of the Organ of CortiOrgan of Corti, which sends a , which sends a signal along the signal along the Auditory NerveAuditory Nerve to the brain. to the brain.

Page 9: Auditory, Tactile, and Vestibular Systems

AlarmsAlarmsCriteria for good alarms:1. Must be heard above background noise (approx 30 dB above)2. Avoid excessive intensity

• Should not be above the danger level for hearing (85-90 dB)• using a very different frequency may help (esp if conflicts with crit #1)

3. Should not be too startling4. Should not disrupt processing of other signals

- Do not want alarm to mask speech or other important signals5. Should be informative, not confusing

- Should communicate the appropriate actions

Sample AlarmsSample Alarms Is each sound discernible?What does each mean?Place mouse over each, do not click

Page 10: Auditory, Tactile, and Vestibular Systems

Alarm DesignAlarm Design1. Conduct environment/task analysis – must understand

what sounds/noises (and their qualities) are associated with the job

2. Make sure alarms are within human’s capability of discrimination by varying on different dimensions: • Pitch (low to high), Envelope (rising/falling pitch), Timbre

(quality), and Rhythm (synchronous vs. asynchronous)3. Design specific qualities of sound

• For example: Use pulses to create unique sound and to give perception of an approaching, then receding sound to create sense of urgency

4. Establish repeating sequence• After initial alert, may be less intense

Page 11: Auditory, Tactile, and Vestibular Systems

False AlarmsFalse AlarmsCry Wolf Syndrome – Human operator fails to respond to alarm due to the large number of false alarms in the past.

To avoid “Cry Wolf Syndrome”:• Set the alarm criterion to be sensitive enough to minimize misses, without increasing false alarms.• May use more complex algorithms to determine true threshold.

• may use more than one signal measure• Train operators on the tradeoffs of false alarms/misses

• understand actual false alarm rates• Use multiple alert levels (denote different urgency states)

Page 12: Auditory, Tactile, and Vestibular Systems

Speech PerceptionSpeech Perception

McGurk Effect – demonstrates top down processing of speech and the importance of redundant visual information for perception

Speech communication measures:• Articulation Index (bottom up) – signal to noise ratio

•(speech dB – background noise dB)• Higher frequencies are more vulnerable to being masked by noise

• Speech Intelligibility Index (top down) – percentage of items correctly heard

Page 13: Auditory, Tactile, and Vestibular Systems

Occupational NoiseOccupational Noise

Dangers of excessive noise: Dangers of excessive noise: • Hearing loss – caused by exposure to loud noises. Some hearing loss is expected with age (higher freqs)

• Loss of sensitivity while noise is present • Temporary Threshold Shift (TTS) – Loss of hearing that lingers after noise is terminated (post-rock concert)

- Tinnitus or ringing in the ears- 100 dB for 100 min causes a 60 dB TTS

• Permanent Threshold Shift (PTS) – Occupational Deafness caused by long term exposure (esp high freqs)

Page 14: Auditory, Tactile, and Vestibular Systems

Noise RemediationNoise Remediation• Signal Enhancement – increase the signal to noise ratio (make signal louder relative to background)• Noise Exposure Regulations – OSHA standards based on Time Weighted Average (calculated with dosemeter)

• if TWA > 85 dB (action level) employer must provide hearing protection • if TWA > 90 dB (permissible exposure level) employer must take noise reduction measures

• The Source – Select equipment and tools that have built in sound dampening• The Environment – Use sound attenuating or sound absorbing materials to reduce transmission and reverberation

•White Noise – Humming noise used to mask distracting sounds• The Listener – Ear protection such as earplugs (internal) or earmuffs (external)

Page 15: Auditory, Tactile, and Vestibular Systems

Vestibular SystemVestibular SystemVestibular SystemVestibular System – detects acceleration forces, maintains upright posture/balance and controls eye position relative to head

Semicircular CanalsSemicircular Canals – detect angular acceleration (rotation) in 3 axes - a crista embedded in a jelly-like material (cupola) is supported by hair cells that bend and fire when the crista moves in response to head rotation.Vestibular Sacs (Utricle & Saccule)Vestibular Sacs (Utricle & Saccule) – detect linear acceleration - hair cells embedded in jelly-like substance lag behind when the head moves. When motion becomes steady, otoliths catch up and hairs no longer bent.

Page 16: Auditory, Tactile, and Vestibular Systems

Motion DisturbancesMotion DisturbancesSpatial Disorientation – vestibular illusion which tricks the brain into thinking body is a different position than it actually is.

Vection – the illusion of self-motion induced my visual cuesMotion Sickness – nausea, disorientation and fatigue attributed to disturbance of vestibular system caused when vision and inner ear send conflicting (decoupled) signals

To experience seasickness without leaving home click on this picture:

Treatments – • Medications – Antihistamines (Dramamine), Dopamine blockers or anti-psychotics (Thorazine), anti-nausea (serotonin) and Scopolamine (anticholinergic)• Behavioral strategies – sit facing front with front window view, eat bland foods such as bread, bananas, rice. If on a boat, stay in middle (less rocking) and look forward at the horizon, not at the waves.

Page 17: Auditory, Tactile, and Vestibular Systems

Sopite SyndromeSopite SyndromeSopite SyndromeSopite Syndrome – motion induced drowsiness• Subset of motion sickness symptoms, but sometimes the sole manifestation• Dangerous because victims often not aware of its onset or the likelihood of onset• Found to affect passengers and operators of cars, trucks, ships, helicopters, planes, and simulators• No known prevention techniques (many motion sickness medications increase drowsiness)• May be a major cause of accidents and military pilot pilot training washout

Page 18: Auditory, Tactile, and Vestibular Systems

Sense of Touch:Sense of Touch:Tactile and HapticTactile and Haptic

TactileTactile – Cutaneous or somatosensory sense provided by receptors just under the skin.

Types of Receptors:Thermoreceptors – detect heat/coldMechanoreceptors – detect pressureNociceptors – detect noxious stimuli (caustic

substances)HapticHaptic – Shape information provided through manipulation of fingers

Human factors application of haptic research

This device provides haptic information to aid in performing a tracking task. The user feels the button pop out and must move the stick in the same direction to maintain course.

Page 19: Auditory, Tactile, and Vestibular Systems

Haptic Responding Haptic Responding ExperimentExperiment

Page 20: Auditory, Tactile, and Vestibular Systems

Vision Substitution SystemVision Substitution SystemWhite, Saunders, Scadden, White, Saunders, Scadden,

Bach-y-Rita, & Collins’ (1970) Bach-y-Rita, & Collins’ (1970) Vision substitution system Vision substitution system converts camera image to converts camera image to pattern of vibration on user’s pattern of vibration on user’s back. Subjects are able to back. Subjects are able to discriminate a wide variety of discriminate a wide variety of different stimulus patterns different stimulus patterns and perceive relative and perceive relative distance. distance.

Human factors application of tactile research

Page 21: Auditory, Tactile, and Vestibular Systems

Tactile Situation Awareness Tactile Situation Awareness SystemSystem

Link to Tactile Research Laboratory: http://www.princeton.edu/~rcholewi/TRLindex.html

Tactile stimulation used to prevent spatial disorientation

Human factors application of tactile research

Page 22: Auditory, Tactile, and Vestibular Systems

Proprioception & Proprioception & KinethesisKinethesis

ProprioceptionProprioception – Receptors in the limbs provide information of limb position in space.

KinesthesisKinesthesis – Receptors in the muscles provide information about limb motion.This subject’s proprioception and

vision are providing conflicting information about his limb position. This not only makes this stacking task difficult, but could lead to motion sickness symptoms.