Façade acoustic design strategy Proposed residential development Irvin Avenue, Saltburn

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1 strategy Proposed residential development Report Number: Version: A Date: 13 th October 2008 Prepared by: Checked by: Andrew Gibson Jack Harvie-Clark Apex Acoustics Limited Design Works William Street Gateshead NE10 0JP Tel: Fax: Prepared for: Rob Sunley DKS Architects The Design Studio Ellerbeck Court Stokesley Business Park Stokesley Middlesbrough TS9 5PT Page 1 of 18

2 1 Revision register Version Changes from previous version Issued by Date Disclaimer: This report has been prepared for the sole benefit, use and information of the client for the purposes set out in the report or instructions commissioning it. The liability of Apex Acoustics Limited in respect of the information contained in the report will not extend to any third party. All concepts, data and proposals are copyright Issued in commercial confidence. 2 Contents 1 Revision register Contents Summary Introduction Proposed internal levels Noise sources and measurements Environmental noise modelling Façade noise transmission Conclusion References Tables Figures Glossary Appendix 1: Equipment used Appendix 2: Calculation of façade noise ingress Appendix 3: WHO Community Noise Guideline Values Report No A Page 2 of 18

3 3 Summary This report has been prepared in support of a Planning Application for a residential development on, adjacent to the railway line. Noise levels affecting the proposed development from rail traffic have been measured, and the facade noise impact modelled. The site is considered to be in Noise Exposure Category B according to PPG 24. Calculated noise levels are used to determine potential façade sound insulation treatments to meet the internal level requirements of the Local Planning Authority. A set of minimum glazing and ventilation strategy options, interpreted from Approved Document F, is proposed as follows: Rooms affected Glazing / mm Potential ventilation All rooms Double glazing Maximum open equivalent area of 12,000 mm 2, AD-F System 1. Summary table of minimum façade sound insulation treatment for all aspects Report No A Page 3 of 18

4 4 Introduction A new two storey residential block of four dwellings has been proposed on the site of former garages on, TS12 1QP. The site location is shown in Figure 1, with its perimeter highlighted in red. The railway line between Marske and Saltburn runs immediately adjacent to the site as shown in Figure 1. The railway line carries both passenger and freight rail traffic. Northern Rail uses the line for passenger services. Cleveland Potash and Corus use the line for freight services. Apex Acoustics has been commissioned to provide advice on the sound insulation of the façade to achieve the internal levels required by the Local Planning Authority. The purpose of this report is to identify the acoustic design parameters agreed with the Local Environmental Health Department, and the manner in which internal noise levels may be achieved in practice. This assessment is based on measurements of rail traffic noise and other noise sources, room and window dimensions on the architects plans, assumptions about room conditions, with glazing and ventilation strategy options proposed in this report. Internal noise transmission and the sound insulation requirements of the Building Regulations are not considered in this report. 5 Proposed internal levels Standards of good and reasonable internal levels are defined in table 5 of BS 8233, Reference 3, as shown in Table 1. The noise criteria for the internal levels from general external sources agreed with the Environmental Health Officer are consistent with these values, and presented in Table 2. These are also consistent with the guideline values from the World Health Organisation, Reference 10, as discussed in Appendix 3. PPG 24, Reference 1, outlines the context for assessing proposed residential accommodation affected by environmental noise. Report No A Page 4 of 18

5 6 Noise sources and measurements Measurements were made of a sample of all train types understood to typically use the track on Wednesday 8 th October The temperature was 24 C and the average wind speed 0.6 m/s. Measurements were made at the position indicated on Figure 1. Train noise was measured using the guidance of Calculation of Railway Noise, Reference 2. The measurement position was located on the site boundary with the railway. The time history of the L Aeq, 1 sec recorded is shown in Figure 4. A representative sample of each train type was measured in each direction, and the sound exposure level associated with each pass-by was calculated. An illustration of the measurements in progress with a freight train is passing is shown in Figure 2. An illustration of a passenger train passing is shown in Figure 3. The Northern Rail train timetable, Reference 13, was used to calculate the number of passenger trains during the daytime and night time period. The number of freight services was calculated from information provided by Cleveland Potash, Reference 14. The train passing frequencies used in the sound exposure level calculations are shown in Table 7. The average daytime and night time levels indicate that the site may be classed as Noise Exposure Category (NEC) B, according to PPG Environmental noise modelling As noise is dominated by railway noise this is modelled using Cadna/A software, Reference 11, to calculate the spectra incident on each façade as required. The software calculates sound propagation outdoors according to ISO 9613, Reference 12. Up to three reflections for each ray are calculated, and ground absorption neglected. Buildings are taken to be perfectly reflective. These are all prudent assumptions in the modelling of noise propagation around the proposed building, resulting in the highest calculated levels incident on the façade. Figure 5 shows a plan view of the noise contours calculated, at 5 db intervals as shown on the accompanying key. Figure 6 shows a 3D perspective view of the same colour contour information. It can be seen that the noise impact on the north façade of the building facing the railway is significantly higher than that on the rest of the proposed building, as may be anticipated. Therefore façade sound insulation is only considered for the railway façade for the kitchen and bedroom accommodation. The overall spectra calculated for noise incident on these rooms during the daytime and night time periods are shown in Table 4. The kitchen is treated as a living space as it forms part of the living room. Report No A Page 5 of 18

6 8 Façade noise transmission The calculation method for façade noise transmission is presented in Appendix 2. The parameters used in the model for this site are discussed below. 8.1 Potential ventilation strategies The proposed development will be required to meet Part F of the Building Regulations, with regard to ventilation provision, as described in Approved Document F (AD-F), Reference 9. Ventilation System 1 of AD-F requires background ventilator provision in accordance with Table 1.2a of AD-F, with intermittent extract from kitchens and bathrooms. Although the developer s proposed ventilation strategy is not known, System 1 requires the largest façade openings, and therefore provides the least potential sound insulation. If this system is adequate, other systems are likely to be more than adequate in providing sufficient sound insulation. On the basis of the guidance in table 1.2a of AD-F, it is calculated that a total equivalent ventilator area of 35,000 mm 2 is required for each dwelling. This should be split between the habitable rooms, in this case two bedrooms and a living room. As a prudent assumption, therefore, an equivalent area of approximately 12,000 mm 2 is assumed in every room for the purposes of the acoustic calculations. The element-normalised level differences are calculated according to Annexe D of EN , Reference 4, for this open area. It should be emphasised that the above is not intended to constitute a ventilation strategy design, which is the responsibility of the mechanical engineers. Assumptions regarding the ventilation strategy are required in order to carry out the acoustic assessment. Once the ventilation strategy is established, if the details very from those described above, the proposed details should be reassessed for acoustic performance. 8.2 Reverberation time From ISO 140-4, Reference 5, the reverberation time is typically 0.5 seconds across the relevant frequency range for a furnished living room. From BRE Digest 338, Reference 6, and the experience of Apex Acoustics, the reverberation time in a furnished room that also contains a bed is typically 0.3 seconds across the relevant frequency range. These values are used respectively for a living room and bedroom. Report No A Page 6 of 18

7 8.3 Glazing Typical thermal double glazing consisting of two 4 mm panes is considered in the calculations. The acoustic performance data is taken from Saint Gobain Glass, Reference 7. Although the data is for a 12 mm air gap between panes, variations between 12 and 20 mm have little effect on the sound reduction index, and these data are therefore also considered valid for 16 mm air gaps. 8.4 Rooms most exposed to noise ingress Calculations are carried out for those rooms most exposed to noise ingress as the worst cases. If these have sufficient sound insulation to meet the internal level criteria, noise levels in less exposed but similarly protected rooms will be lower and therefore also comply with the Planning requirements. The most exposed rooms are those with the largest ratio of window area to room volume, as well as those closest and most exposed to the noise sources. The room and window dimensions are taken from the architect s plans, Reference 8. The rooms used in the calculations are indicated in Figure 7. Calculations are presented for the following rooms: Kitchen Lounge Table 5. Bedroom 2 Table 6. 9 Conclusion Noise levels affecting the proposed development have been measured and the noise impact on different façades has been modelled. The minimum façade sound insulation treatment for each portion of the proposed building has been calculated. On the basis of the measurements, assumptions and details in this report, it is calculated that the minimum provision as shown in the summary table is required. There is a criterion for L Amax values not regularly exceeding 45 db(a) identified in BS However, as discussed in Appendix 3, researchers believe that up to instances of the L Amax exceeding 45 db(a) are acceptable before sleep disturbance occurs. As there are fewer than ten trains in the night time period, this criterion is not considered appropriate to apply to the levels for this development. Report No A Page 7 of 18

8 10 References 1. Planning Policy Guidance: Planning and Noise, PPG 24, Department of the Environment. 2. Calculation of Railway Noise, Department of Transport, BS 8233: 1999, Sound Insulation and noise reduction for buildings Code of practice. 4. BS EN :2000, Building Acoustics Estimation of acoustic performance of buildings from the performance of elements Part 3: Airborne sound insulation against outdoor sound. 5. BS EN ISO 140-4: 1998 Acoustics Measurement of sound insulation in buildings and of building elements Part 4: Field measurements of airborne sound insulation between rooms. 6. Building Research Establishment Digest Saint Gobain Glass data 8. DKS Architects Project No Dwg No. P04(B) 9. Approved Document F 2006 Edition, The Building Regulations Guidelines for Community Noise, Edited by Birgitta Berglund, Thomas Lindvall, Dietrich H Schwela. World Health Organisation, Cadna/A environmental noise modelling software, version , Datakustik GmbH. 12. ISO 9613: Acoustics - Attenuation of sound during propagation outdoors. 13. Northern Train Times 18 th May to 13 th December 2008 Newcastle and Bishop Auckland to Saltburn. 14. Train timetable data from Cleveland Potash, Cleveland, (private communication). Report No A Page 8 of 18

9 11 Tables Criterion Reasonable resting / sleeping conditions Typical situation Design range / L Aeq, T, db Good Reasonable Living rooms Bedrooms Table 1: Good and reasonable internal levels as defined in BS Situation Proposed upper limits, L Aeq, T / db Living rooms, daytime 35 Bedrooms, night time 30 Table 2: Upper limits for daytime and night time internal levels, as agreed with the LPA. Parameter Noise level, L Aeq, T / db Daytime, L Aeq, 16 hr 58 Night time, L Aeq, 8 hr 53 Table 3: Calculated noise levels on site boundary for NEC Classification Octave Band centre frequency / Hz Facade Freefield Level db(a) Kitchen Living Daytime, L Aeq, 16 hr Bedroom 2 Night time L Aeq, 8hr Table 4: Calculated noise levels affecting most exposed living areas and bedrooms Report No A Page 9 of 18

10 Kitchen Lounge Volume, V /m Window area, S /m Reverberation Time, T /s 0.5 Open area / mm 2 12,000 Octave centre frequency db(a) Daytime freefield Noise, L 1in /db(a) (12) 4, Glazing SRI Equation 1, L 2 /db(a) Open area D n,e Equation 2, L 2 /db(a) Combined noise through window and vent/ db(a) 28 Table 5: Kitchen Lounge Bedroom 2 Volume, V /m Window area, S /m Reverberation Time, T /s 0.3 Open area / mm 2 12,000 Octave centre frequency db(a) Daytime freefield Noise, L 1in /db(a) (12) 4, Glazing SRI Equation 1, L 2 /db(a) Open area D n,e Equation 2, L 2 /db(a) Combined noise through window and vent/ db(a) 24 Table 6: Bedroom 2 Train frequency Passenger Daytime Passenger Night time Freight Daytime Freight Night time Monday -Friday Saturday Sunday Table 7: Passenger train frequency data Report No A Page 10 of 18

11 12 Figures Measurement Position Figure 1: Site location and measurement position. Development site outlined in red Report No A Page 11 of 18

12 Façade acoustic design Measurement Location Figure 2: Microphone at measurement position whilst freight train passes. Figure 3: Picture of passenger train passing the site. Report No A Page 12 of 18

13 :40:00 13:50:00 14:00:00 14:10:00 14:20:00 14:30:00 14:40:00 14:50:00 15:00:00 15:10:00 15:20:00 15:30:00 15:40:00 15:50:00 Figure 4: Time history of the L Aeq, 1 sec recorded for the day time period. Railway Line Proposed Development Figure 5: Plan view of noise impact model and colour contour key, daytime noise. Report No A Page 13 of 18

14 Proposed Development Railway Line Figure 6: 3D perspective view of noise impact model for daytime noise. Report No A Page 14 of 18

15 Bedroom 2 Kitchen Living Figure 7: Layout plan with rooms indicated for which calculations are presented. Report No A Page 15 of 18

16 13 Glossary The British Standards and other documents referenced should be consulted for definitions of terms and a more extensive glossary. See also Noise Noise is commonly defined as unwanted sound, and is measured in units of decibels, db. The range of audible sound is generally taken from a threshold of hearing of 0 db to the threshold of pain at 120 db. Because it is a logarithmic quantity, two equal sources of sound, if added together will result in an increase in level of 3 db, e.g. 50 db + 50 db = 53 db. A 10 db increase in sound pressure level is generally perceived as a doubling of loudness, while a change of 1 db is generally only perceptible under controlled conditions. Frequency Frequency (or pitch) of sound is measured in cycles/ second, denoted Hertz. The range of frequencies audible to the human ear is from around 20 Hz to Hz (18 khz). The capability of a person to hear higher frequencies decreases with age. The ear is more sensitive to medium frequencies than high or low frequencies. A-weighting To take account of the varying sensitivity of the ear to different frequencies, the most common weighting scale that has been adopted is called A-weighting, and denoted db(a). This provides the best correlation with the perception of loudness or subjective response to noise level for low to average noise levels. Continuous equivalent noise level, L eq, T External noise levels are rarely steady but rise or fall due to the activity in the area - cars, voices, planes, birdsong, etc. Subjective response to different noises has been found to vary depending on its temporal distribution (i.e. its variation with time). The continuous equivalent level is that which contains the same sound energy over the stated time period as the time-varying noise level under consideration. Statistical indices are also used to describe a varying noise level with single figure numbers. L A10,T The A-weighted level of noise exceeded for 10 % of the specified measurement period (T). It gives an indication of the upper limit of fluctuating noise such as that from road traffic. L A10, 18 h is the arithmetic average of the 18 hourly L A10, 1h values from to Report No A Page 16 of 18

17 14 Appendix 1: Equipment used Equipment Model Serial no. Sound Level Meter Norsonics Calibrator Norsonics Both meter and calibrator have current calibration certificates traceable to national standards. 15 Appendix 2: Calculation of façade noise ingress The noise level in a room due to sound penetrating a façade element may be calculated according to BS EN and BS 8233 from: Where: S 2 = L1, R + 10 Log + 10 Log T + V ( ) 11 L in Equation 1. L 2 = noise level in room due to sound through façade portion of area S and mean sound reduction index R, db L 1, in = external freefield noise level at the position of the façade, db. R = sound reduction index of portion, db S = area of façade portion, m 2. V = room volume, m 3 T = reverberation time, s. For small façade components, such as ventilators, the noise level in a room may be calculated according to the same standards as above from: Where: ( V ) + 10 Log( ) 21 L2 = L1, Dn, e 10 Log T + in Equation 2. D n, e = element-normalised sound level difference of the ventilator. Other components have the same meaning as above. The sound reduction of the masonry portion of the facade is much higher than that of the glazing and ventilation provision. Therefore noise penetration through the masonry is disregarded as insignificant compared to noise penetration through the glazing and ventilation provision. The noise penetration through the vents and the glazing is calculated as above and then combined in each frequency band to give an overall internal level from the external sources by these routes. Calculations are carried out in five octave bands as indicated in BS Report No A Page 17 of 18

18 16 Appendix 3: WHO Community Noise Guideline Values Section of WHO Community Noise Guideline Values discusses how electrophysiological and behavioural methods have demonstrated that both continuous and intermittent noise indoors lead to sleep disturbance. The more intense the background noise, the more disturbing is its effect on sleep. Measurable effects on sleep start at background noise levels of about 30 db L Aeq. Physiological effects include changes in the pattern of sleep stages, especially a reduction in the proportion of REM sleep. Subjective effects have also been identified, such as difficulty in falling asleep, perceived sleep quality, and adverse after-effects such as headache and tiredness. Sensitive groups mainly include elderly persons, shift workers and persons with physical or mental disorders. Where noise is continuous, the equivalent sound pressure level should not exceed 30 db(a) indoors, if negative effects on sleep are to be avoided. When the noise is composed of a large proportion of low-frequency sounds a still lower guideline value is recommended, because low frequency noise (e.g. from ventilation systems) can disturb rest and sleep even at low sound pressure levels. It should be noted that the adverse effect of noise partly depends on the nature of the source. A special situation is for newborns in incubators, for which the noise can cause sleep disturbance and other health effects. If the noise is not continuous, L Amax or SEL are used to indicate the probability of noise induced awakenings. Effects have been observed at individual L Amax exposures of 45 db or less. Consequently, it is important to limit the number of noise events with a L Amax exceeding 45 db. Therefore, the guidelines should be based on a combination of values of 30 db L Aeq,8h and 45 db L Amax. However, Section 3.4 of the WHO guidelines note that for a good sleep, it is believed that indoor sound pressure levels should not exceed approximately 45 db L Amax more than times per night (Vallet & Vernet 1991). To protect sensitive persons, a still lower guideline value would be preferred when the background level is low. Sleep disturbance from intermittent noise events increases with the maximum noise level. Even if the total equivalent noise level is fairly low, a small number of noise events with a high maximum sound pressure level will affect sleep. Therefore, to avoid sleep disturbance, guidelines for community noise should be expressed in terms of equivalent sound pressure levels, as well as L Amax / SEL and the number of noise events. Measures reducing disturbance during the first part of the night are believed to be the most effective for reducing problems in falling asleep. Report No A Page 18 of 18