BS8233:1999 Sound Insulation and Noise Reduction in Buildings – A Code of Practice

This states that 55 LAeq or lower is indicative of good amenity within gardens, which is based on advice from the World Health Organisation Community Noise Guidelines to lead to a low level of annoyance. We would normally use a 1-hour time period over which to evaluate noise sources against this criterion.

PPG24 Planning and Noise

This provides guidance on the acceptability of ambient noise levels when considering new house developments within an area. The situation we have here (pre-existing housing with new potential noise source) is not therefore one that is necessarily suitable to directly apply the standard. The standard does provide a relevant reference.

In essence PPG24 characterises ambient noise into four Noise exposure categories (NECs) with NEC A being the lowest noise levels (noise below 55 dB LAeq,16hr). Where ambient noise levels are below this level it, in effect, states that noise need not be considered as a determining factor in granting planning permission.

BS4142:1997 – Method for Rating Industrial Noise Affecting Mixed Residential and Industrial Areas

This considers the contribution from the noise source in question compared to background noise. We have reservations about using this standard to evaluate noise from people talking and shouting – it is a standard intended to be used for the assessment of industrial noise and is therefore more applicable to building services noise. In essence BS4142 states that the likelihood of complaint, is a function of the difference between the noise from the source in question and the background noise level. If this difference is in the region of 10 dB or more, then according to the standard, complaints are likely. A difference of around 5 dB is of marginal significance, with the lower the value the less the likelihood of complaints. If the rating level is 10 dB less than the background noise level, then complaints are unlikely.

3.0 EXISTING NOISE CLIMATE The existing noise climate has been measured over an extended period between Tuesday 22nd April and Thursday 1st May 2008 at a location considered to represent the nearest residential boundary to the proposed school. During the measurement period the weather was changeable, with the majority of this period having good conditions for noise survey work. The results are summarised in the appendices A and B and further details are available on request. The measurements taken have determined the existing noise climate at the monitoring location to be as described in Table 1. The monitoring location is considered to be representative of the site, and was chosen as a secure location where equipment could be left unattended. The level of sound is constantly varying with space and with time, hence it is necessary to use statistical measurement parameters. The parameters used are LAeq and LA90 and are a time-average of the noise level at the measurement position. The LAeq provides a measure of the equivalent average level, in essence the ambient noise, whereas the LA90 shows the 90th percentile (the level exceeded for 90% of the time) and gives a measure of the background noise level.

Min to Max Sound Pressure Level dB(A) Weekday Weekend

07:00 to 23:00 23:00 to 07:00 07:00 to 23:00 23:00 to 07:00 Parameter 16 Hr Avg.

1 hr Avg.

8 Hr Avg.

1 hr Avg.

16 Hr Avg.

1 hr Avg.

8 Hr Avg.

1 hr Avg.

LAeq (Ambient) 53 to 59 39 to 67 41 to 48 27 to 56 45 to 47 37 to 53 41 33 to 46

LA90 (Background) 41 to 47 31 to 59 33 to 39 23 to 46 40 30 to 45 36 27 to 41

TABLE 1: SUMMARY OF MEASURED EXISTING NOISE LEVELS AT SITE DURING 1 WEEK The night time is as expected, quieter than the day time. It is interesting to note that there is a significant difference between the noise experienced at the weekend to the weekdays, and a large range of noise levels at all times of day and night (i.e. the noise climate is quite variable) which is, we believe to be largely as a result of the school use of these fields for sporting activities currently.

4.0 MEASURED NOISE LEVEL OF SCHOOL OCCUPATION In addition to the extended noise monitoring undertaken at site, we have also taken measurements of the school field in use for a whole year group games lesson. We observed noise levels at the boundary of typically 47 dB(A) LAeq while the lesson was in progress, and typically 45 dB(A) LAeq before and after the lesson. These level correlate well with the logged data summarised in section 3.0. We have also taken measurements of noise in a location close to an active game of softball with the same students. The levels measured are correspondingly higher due to the proximity of the participants. We have used this data to determine whether our modelling accuracy is acceptable.

5.0 PREDICTED NOISE LEVELS OF NEW SCHOOL OCCUPATION 5.1 Vocal Output Building Bulletin 93 (Acoustics in Schools - A Design Guide) provides a good reference for the volume of speech. This is presented as sound pressure levels and sound power levels in Section 4, Figure 4.1 and are summarised in Table 2.

Sound Level Vocal Effort (Watts) dB(A) at 1m

Normal 10 µW 60 Raised 100 µW 70

Shouting 1000 µW 80

TABLE 2: TYPICAL VOLUME OF DIFFERING LEVELS OF SPEECH In effect this means that one person talking in a raised voice equals 10 people talking normally and that one person shouting equals 100 people talking with a normal voice effort. The total acoustic output is a function of,

- The speech level (as above) - The number of people speaking - The duration of the conversation/speech

It is feasible that people can be speaking while another is shouting, and hence there are many variables that need to be accounted for in deriving a model of noise from school occupation. We

have used experience and measurement of the noise from the school playing fields to calibrate our modelling.

5.2 Noise Impact – Typical Cases We have attempted to model a number of example cases of how the area surrounding the school and all-weather pitch may be used. The multi-use games area is located further from the sensitive locations used in this assessment, and will be a proportionally much quieter noise source compared to the all weather pitch. The contribution made from the multi-use games area will be minor in comparison to the all weather pitch and hence the multi-use games area is not specifically shown in the following assessment. The locations used for assessment are shown as a marked-up plan in the appendix to this letter. To do so we have assumed that the average location for the sound produced is always in the centre of the all weather pitch (i.e. that people are equally distributed around the pitch on average). This is considered a reasonable assumption of practical use, but it does not reflect the directivity of spectators, or well represent the variability in location that may be possible.

Persons Taking Part Spectators % Time (per person) % Time (per person)

Case No Off Normal Raised Shouting

No Off Normal Raised Shouting

Total Sound Power Level

dB LWASchool Lessons [1] 62 20 10 1 0 0 0 0 91

Competitive Match 25 10 3 2 50 15 2 2 93

Community Training 35 10 2 1 10 15 2 0 87

TABLE 3: APPARENT SOUND POWER LEVEL OF TYPICAL ACTIVITY ON SCHOOL SITE [1] The percentages of people talking have been adjusted to correlate with measured data mentioned in section 4.0. It is expected that noise levels will be some 2-3 dB(A) higher during competitive events than for training. This is in-line with our direct experience. It should also be noted that the small percentages of raised voice and shouting represents an almost continuous noise level when averaged over the measurement period. For the purposes of this assessment we have considered these cases in predicting the resultant effect at the nearest residential property, and have also “calibrated” our model against the measured data. To predict the resultant noise level at a particular position there are numerous corrections that could be considered for attenuation effects. We have ignored the attenuations due to weather and meteorological effects, ground absorption, screening and barrier effects and have used only distance attenuation due to geometrical spreading. This is, we feel a conservative approach. It is also necessary to consider the use over a 16-hour period to enable comparison to the PPG24 criterion detailed above. For the purposes of this assessment we have considered the following typical cases - Case A: Lessons for 5 hours during school day - Case B: Lessons for 5 hours during school day plus 2 hours of competitive match - Case C: Lessons for 5 hours during school day plus 4 hours of community training

5.3 Predicted Noise Levels At Nearest Residential Property Table 4 summarises our predicted noise levels at the nearest noise sensitive location. These values are used for comparison against the assessment criteria. As these levels are predicted for the nearest resident (i.e. the apparent worst case), other positions which have greater distance between them and the school can be expected to experience lower levels of noise.

Loudest Predicted Level (LAeq,1hr) Predicted Level (LAeq,16hr)

Location Case A Lessons

Case B Lessons +

Match

Case C Lessons + Training

Case A Lessons

Case B Lessons +

Match

Case C Lessons + Training

3 Uplands Close 41 43 41 {Note 1} 36 38 37

64 Glenleigh Park Road 47 49 47 (Note 1} 42 44 43

TABLE 4: PREDICTED 1 HR AND 16 HR AVERAGE NOISE LEVELS RESULTING FROM USE OF SCHOOL FIELDS FROM OUR ACOUSTIC MODEL {Note 1} The contribution from a 1 hr period of lessons being greater than from 1hr of training

6.0 ACCEPTABILITY OF PREDICTED NOISE LEVELS 6.1 BS8233 – External Amenity Criteria It can be readily seen that the 55 dB LAeq,1hr criteria is achieved for all of the expected cases in Table 4, and on this basis the external amenity afforded to the local residents will remain of a “good” standard and a low level of annoyance can be anticipated.

6.2 PPG24 – Planning Policy Criteria It can be seen from the predicted levels in Table 4 that the PPG24 LAeq,16hr criterion for of 55 dB(A) LAeq / NEC A is expected to be achieved when the school site is occupied. We would re-iterate that this criterion would be of more relevance if the school was already present and housing were under consideration near-by. It is however indicative of an acceptable situation. On this basis the external amenity afforded to the local residents would remain of a “good” standard.

6.3 BS4142 – Annoyance Criteria Individual 1hr activities are expected to be as much as 16 dB(A) above the quietest measured background noise levels during the daytime (31 dB(A) LA90), but more typically some 6-9 dB(A) above the prevailing background noise levels. This excess would be indicative of “leading to a likelihood of complaint”, although at other times the activity noise is lower than the background noise, by some 10 dB(A) and would be indicative of leading to a “low likelihood of complaint”. We feel it is worth bearing in mind that BS4142 assessment basis picks on the lowest measured noise level at any time, and not the actual ambient noise level when the intrusive noise source is present. Given the variable nature of the noise sources in question for this site, we are of the opinion that applying these annoyance criteria is particularly challenging. The levels predicted in Table 4 are comparable to, and in many cases lower than the existing LAeq noise levels experienced at site and in our opinion it is hard to see how this can be any worse than the existing situation during the daytime.

7.0 BS4142 PLANT NOISE ASSESSMENT Following the procedure in BS4142, a noise limit for the new building services plant can be determined. We have based our assessment on a plant noise contribution that is 5 dB(A) less than the prevailing background noise so as to lead to a low likelihood of complaint. The plant room details are not finalised at this stage, and consequently it is not possible to provide limits for individual items of plant. We have provided limits that would apply to the whole installation. We have derived a noise limit for the daytime hours (07:00 to 23:00). This is on the assumption that the school would unlikely operate the plant during the night time and hence it would be overly onerous to design to a night time limit for all times. The plant room is proposed in the South East corner of the new building beneath a first floor overhang. The plant room would have external façade to the East and South elevations. Based on the prevailing LA90,1 hr during the daytime of 40 dB(A) the plant noise limit at the boundary would be 35 dB(A). The distance to the nearest residential boundary is c. 20 m. The overhang has the effect of limiting the geometrical spreading effects of noise radiated from the plant room, which we have taken into account. We have made the assumption that approximately half of the plant room external perimeter would be louvered. This is subject to review during detail design of the plant room. A plant noise limit of 54 dB(A) at 1 m from the louvres of the plant room can be expected to lead to a low likelihood of complaint. We note that increases to this noise level of up to 10 dB(A) would be of marginal significance, and an increase of greater than 10 dB(A) would likely lead to complaint. Also worth noting is we have based the limit on the measured 1 hr average LA90, and so some variation in audibility of the plant noise may be apparent as the background noise varies over periods of time shorter than the averaging used in the BS4142 assessment.

8.0 CONCLUSION Having undertaken an assessment, using what we consider is a robust approach; we have concluded that adverse impact of the school site on the local residential property is at worst marginal during the daytime. Plant noise limits have been proposed to lead to a low likelihood of complaint. Please advise if further details are required at this stage on any aspect. Yours faithfully, Hawksmoor Engineering Ltd Ian Matthews

APPENDIX A – SUMMARY OF LOGGED NOISE LEVELS AT SITE

9.0 APPENDIX B – KEY LOCATIONS ON SITE

APPENDIX C – EXAMPLE CALCULATIONS

APPENDIX D – SUMMARY TABLE