Premier Inn, Rotherham - Noise Ingress Assessment
Premier Inn, Rotherham - Noise Ingress Assessment
Prepared by: Checked by: Jon Willmott MIOA Mike Hewett MIOA Regional Director Principal Acoustic Engineer Approved by: Mike Hewett MIOA Regional Director Premier Inn, Rotherham - Noise Ingress Assessment Rev No Comments Checked by Approved by Date Initial Issue June 2011 1 1 New York Street, Manchester, M1 4HD Telephone: 0161 601 1700 Website: http://www.aecom.com Job No 12312312 Reference Rp1V1 Date Created June 2011 This document has been prepared by AECOM Limited for the sole use of our client (the “Client”) and in accordance with generally accepted consultancy principles, the budget for fees and the terms of reference agreed between AECOM Limited and the Client.
Any information provided by third parties and referred to herein has not been checked or verified by AECOM Limited, unless otherwise expressly stated in the document. No third party may rely upon this document without the prior and express written agreement of AECOM Limited.
JW - 02062011R - PI Rotherham Rp1V1
1 Introduction ___ 1
2 External Noise Survey ___ 2
2.1 Introduction ___ 2
2.2 Site and Surroundings ___ 2
2.3 Noise Measurements ___ 4
2.4 Methodology ___ 5
2.5 Results ___ 6
3 Assessments ___ 7
3.1 Noise Ingress to Guestrooms ___ 7
3.1.1 Criteria ___ 7
3.1.2 Assessment ___ 7
3.1.3 Window Units ___ 7
3.1.4 Trickle Ventilation ___ 7
3.1.5 External Wall ___ 8
3.2 Noise emission from the building to nearby noise sensitive receptors ___ 8
4 Conclusions ___ 9
Appendix A: Glossary of Acoustic Terms ___ 10
Table of Contents
AECOM Noise Ingress Assessment 1 Capabilities on project: Building Engineering 1.1 A new Premier Inn is proposed on a site on the Phoenix Riverside industrial area in Rotherham. The hotel will be a new building situated next to offices, a busy road a railway line and other industrial premises. 1.2 AECOM Acoustics was commissioned to undertake an external noise survey and preliminary site review to identify likely noise control measures applicable to the new hotel. 1.3 An external noise survey was undertaken at the site to determine prevailing ambient noise levels at representative locations and times.
Data from the survey was then used to determine sound reduction specifications for facades, glazing and ventilation apertures.
1.4 This report details the measured external noise levels, the design criteria and recommendations relating to noise control. 1.5 A glossary of the acoustic terms used in this report is given in Appendix A. 1 Introduction
AECOM Noise Ingress Assessment 2 Capabilities on project: Building Engineering 2.1 Introduction 2.1.1 This section provides details of the external noise survey undertaken on the 13th April 2011. Attended noise level measurements were made to determine prevailing ambient noise levels at representative locations and times on the proposed hotel site.
2.2 Site and Surroundings 2.2.1 The Phoenix Riverside site, proposed for the hotel is located between the River Don and Sheffield Road. Between the site and the road are existing office buildings and car parks. To the west of the site is a railway line approximately 200 m from the location of the proposed building and to the north, a smelting works was observed approximately 400 m away. 2.2.2 Figure 2.1 gives a site plan of the area showing the location of the building and the other key noise sources. Figure 1: Site Layout & Existing Noise Sources 2 External Noise Survey Railway Line Sheffield Road N NOT TO SCALE Smelting works
AECOM Noise Ingress Assessment 3 Capabilities on project: Building Engineering 2.2.3 Figure 2.1 shows the smelting works observed from the area of site proposed for the new hotel: Figure 2: View Of The Smelting Works 2.2.4 Figure 2.3 shows the railway line observed from the area of the site proposed for the new hotel:
AECOM Noise Ingress Assessment 4 Capabilities on project: Building Engineering Figure 3: View Of The Railway Line 2.3 Noise Measurements 2.3.1 Noise measurements were made to determine the noise incident upon the different facades of the hotel during noisiest parts of the day (07:00 – 23:00) and night (23:00 – 07:00).
2.3.2 The noisiest parts of the day and night were considered to be morning rush hour (07:00 – 09:00) and the latter part of the night (05:00 – 07:00). 2.3.3 Noise measurements were undertaken on parts of the site which represent the locations of the different facades of the hotel. These locations were chosen to establish any variation in acoustic conditions for each facade. Figure 4 shows the chosen measurement locations
AECOM Noise Ingress Assessment 5 Capabilities on project: Building Engineering Figure 4: Measurement Locations 2.4 Methodology 2.4.1 Attended noise level measurements were made at locations 1 and 2 during the noisiest parts of the day and night time periods. 2.4.2 Table 2.1 lists the equipment used. Equipment Item Serial Number Rion NA-28 Sound Level Meter 570400 Rion NC-74 Sound Calibrator 34973231 Table 2.1: Survey Equipment 2.4.3 The sound level meter was field calibrated prior to and on completion of the survey period. No drift in calibration was observed. Measurements were made in free-field conditions with the microphones placed approximately 1.5 m above the ground at each location.
2.4.4 Measurement duration was 20 minutes. 2.4.5 Weather conditions at the start of the survey were 4° C and 75% RH with clear skies and a very light north-easterly wind. These conditions were suitable for measurement of representative ambient and background noise levels at the site. Measurement Location 1 Measurement Location 2
AECOM Noise Ingress Assessment 6 Capabilities on project: Building Engineering 2.5 Results 2.5.1 Table 2.2 gives a summary of the measured noise levels. Measurement Location Start Time Noise Measurements LAeq LAFmax 1 05:30 54 67 2 05:50 55 63 1 06:10 56 67 2 06:30 57 64 1 06:51 56 65 2 07:10 56 63 1 07:30 59 69 2 07:50 59 64 1 08:10 56 64 2 08:31 59 66 1 08:55 58 65 2 09:20 57 64 Values are sound pressure levels in dB re 20 µPa Table 2.2: Summary of Measured Noise Levels 2.5.2 Of the above results, the LAeq levels are likely to dictate.
They resulted from traffic noise on Sheffield Road, distant motorway noise and noise from the distant smelting works.
2.5.3 During the day, background noise levels are dominated by traffic noise from Sheffield Road. However, from approximately 06:00 onwards noise from the distant smelting works is clearly audible and provided some contribution to the overall acoustic environment. 2.5.4 Although infrequent during the survey, freight train movements along the adjacent railway line generated audible short term noise events, however the levels were not considered to be particularly high and not high enough to be considered the cause of the measured maximum noise levels. Noise from this particular source was observed during the day and night time period.
2.5.5 A full record of the survey results has been kept on file and will be supplied on request if required.
AECOM Noise Ingress Assessment 7 Capabilities on project: Building Engineering 3.1 Noise Ingress to Guestrooms 3.1.1 Criteria 18.104.22.168 The Premier Inn Turnkey Specification requires that internal noise levels within guest rooms from external sources is controlled to 35 dB LAeq during the day (07:00-23:00) and 30 dB LAeq during the night (23:00-0700). Furthermore, noise from regular noise events should be controlled to 45 dB LAFmax during the night-time.
22.214.171.124 The specification also requires that noise associated with any other tenancy should not exceed NR20 L10 (23:00-07:00) within guestrooms.
3.1.2 Assessment 126.96.36.199 Noise levels around the parts of the site proposed for the hotel are fairly consistent and subsequently the noise incident on each facade will be similar. Therefore, one sound insulation specification has been determined applicable to all facades of the proposed hotel. 188.8.131.52 The following sound insulation recommendations specifications must be achieved for each of the following facade elements in order to achieve internal noise levels which meet the Premier Inn Generic Turnkey Specification: 3.1.3 Window Units 184.108.40.206 Window units including frames, seals and fixings must achieve the sound reduction indices given in Table 3.1.
Octave Band Centre Frequency (Hz) 63 125 250 500 1k 2k 4k 8k Sound Reduction Index (dB R) 18 24 20 25 35 38 35 45 Table 3.1: Window Unit Sound Reduction Specification 220.127.116.11 The performance specification for windows should be achieved when measured in accordance with BS EN ISO 140-3 – ‘Laboratory measurement of airborne sound insulation of building elements’.18.104.22.168 It is suggested that the supplier of the glazing provides suitable evidence of the window unit’s sound insulation. Typically such evidence would take the form of a formal laboratory test report on the complete system. 22.214.171.124 The following glazing build-up would typically be required to meet the required sound reduction:
- 4 mm pane + 12 mm airgap + 4mm pane with suitable frame and seals 3.1.4 Trickle Ventilation 126.96.36.199 In terms of ventilation, the current preference for Premier Inns is to adopt a mechanical extract and supply system for each guest room. However, if preferred, a natural ventilation system may be adopted using trickle ventilators for background ventilation.
188.8.131.52 The following specification is based on one trickle ventilator unit used per guestroom. If greater numbers of units are used per room the specification must be revised. The acoustic performance required for the single trickle ventilator option is as follows: Octave Band Centre Frequency (Hz) 63 125 250 500 1k 2k 4k 8k Element Normalised Level Difference dB (Dne) 35 41 37 35 35 42 43 43 Table 3.2: Trickle ventilator Sound Reduction Specification 3 Assessments
AECOM Noise Ingress Assessment 8 Capabilities on project: Building Engineering 184.108.40.206 The performance specification for windows should be achieved when measured in accordance with BS EN ISO 140-10 – ‘Laboratory measurement of airborne sound insulation of small building elements’.
220.127.116.11 The above specification could typically be achieved with an RW Simon EHA acoustic trickle ventilator. However, many other manufacturers offer products with equivalent performances. 3.1.5 External Wall 18.104.22.168 At this stage the proposals for the external wall construction are yet to be confirmed however, it is assumed that the construction will comprise an SFS system including a twin layer of plasterboard on the inner leaf and a cementitious render system on the outer element.
22.214.171.124 This arrangement is expected to be sufficient from a sound insulation perspective however an acoustic review of the proposed construction should be undertaken during the forthcoming design stages. 3.2 Noise emission from the building to nearby noise sensitive receptors 3.2.1 It is our understanding that the Local Planning Authority have raised no concerns regarding the control of noise ingress to the proposed development. 3.2.2 From our observations whilst on site and other research undertaken, no residential properties are in the proximity of the proposed hotel. Therefore an assessment of building services in accordance with BS 4142 is not required.
3.2.3 However, noise and vibration from building services must be controlled in order to minimise the potential disturbance to the users of the hotel. The following recommendations must be implemented.
- Noise from building services mounted on the roof must not exceed 50 dB LA at the edge of any part of the roof.
- The roof top plant must not be located directly above guestrooms and must be supported from major structural elements of the building using appropriately selected anti-vibration mounts. The construction of the top floor roof and ceiling must also be adequate to control ingress of the expected rooftop ambient plant noise levels. Current design proposals show the roof top plant located above the central corridor not above guestrooms.
- Experience at other Premier in sites indicates that ambient noise levels on the roof might could exceed 70 dB LAeq. To protect the rooms around the units from noise breaking via the roof a substantial construction will be required. Ideally the roof structure should comprise concrete as opposed to a lightweight arrangement which would require additional sound insulation measures to enhance its overall acoustic performance.
- The structural mounting conditions for items of rooftop plant must be sufficient to provide a level of vibration isolation of at least 95 % at all frequencies of concern. This level of isolation provided by the ballast and insulation alone however, in most cases proprietary spring isolators are required. Further design work will be required in the forthcoming design stages to confirm the isolation requirements.
3.2.4 Despite no nearby noise sensitive receptors in close proximity to the proposed hotel, a building services noise limit has been set to achieve appropriate internal noise levels within guestrooms, in accordance with the Premier Inn criteria.
AECOM Noise Ingress Assessment 9 Capabilities on project: Building Engineering 4.1 AECOM Acoustics have undertaken a noise survey and provided outline acoustic design recommendations for the proposed Premier Inn, Rotherham. Noise level data measured at the site was used to determine the sound insulation performance requirements for glazing and ventilation systems on different facades.
4.2 An external noise survey was undertaken on the 13th April 2011 to determine prevailing ambient noise levels at representative times and locations. The site is subject to noise from Sheffield Road, a nearby railway line and a distant smelting works. However none of the noise sources present any significant issues in terms of noise control. 4.3 Based on the results of the external noise survey, noise ingress predictions were undertaken to determine the sound insulation performance requirements for glazing needed to meet the Premier Inn internal noise limit specifications. 4.4 Recommendations were given regarding the acoustic design of the hotel facades including sound insulation performance specifications for glazing and trickle ventilation.
4.5 In the absence of any noise sensitive receptors in close proximity to the location of the proposed hotel, noise emission limits for external building services were based on achieving a suitable external noise level at the facades of the hotel’s guestrooms, to achieve internal noise levels in guestrooms in accordance with the Premier Inn criteria. 4 Conclusions
AECOM Noise Ingress Assessment 10 Capabilities on project: Building Engineering This section provides a layperson’s explanation of the acoustics terms that commonly appear in reports. It is not intended to give full scientific definitions and explanations or go into detail on how and why things are as they are.
Some obsolete terms and abbreviations have been included as they still appear in documents from time to time. Jargon Buster Many words have more specific meanings when used in acoustics than in every-day language. sound is used to describe the physical phenomenon of the transmission of energy through gaseous or liquid media via rapid fluctuations in pressure.
vibration is used to describe the transmission of energy through solid media by oscillation level used solely to describe values measured in decibels loudness is the human perception of the level of sound noise has no strict definition and is often used interchangeably with sound however it is usually taken to mean unwanted sound index a value based on the mathematical processing of raw data indicator a value used to indicate the likelihood of a particular response of effect eg. L10,18hr is an index based on statistical processing of sound pressure data that is used as an indicator for road traffic noise response.
weighted values modified to reflect sensitivities at particular frequencies. apparent measured in situ standardised a generalised value based on an in-situ measurement with a correction based on a space with standard reverberation normalised a generalised value based on an in-situ measurement with a correction based on space with standard absorption area insulation resistance to the passage of airborne sound isolation resistance to the passage of vibration insertion loss dynamic insertion loss static insertion loss actual reduction in noise achieved by a structure or system in situ in a ducted system the actual reduction in sound achieved by an attenuator in real flow conditions in a ducted system the actual reduction in sound achieved by an attenuator in the absence of fluid flow attenuation amount by which sound or vibration is reduced when passing through a structure or system directivity the amount by which a source radiates more sound in one direction than another.
Appendix A: Glossary of Acoustic Terms
AECOM Noise Ingress Assessment 11 Capabilities on project: Building Engineering decibels dB The decibel is not a true measurement unit nor is it exclusive to acoustics. The decibel is a logarithmic ratio of two values of a variable. Decibels are used because they can represent very wide ranges of ratios (from trillionths and billionths to billions and trillions) with a small range of decibel values. Decibels can be used to represent measured values by using a known reference value in the ratio. When using decibels to measure something it is therefore important to specify what variable is actually being measured and what reference level has been used.
This is done by adding a reference value statement in the form “dB re x units”, where the units indicate the variable being measured and x is the reference value. Decibels are used in acoustics because the human ear responds to sound in a logarithmic way and the quantities measured in acoustics vary over wide ranges. However, decibels are used in acoustics to measure several different things which it is important not to confuse with each other.
To avoid confusion there is a notation system that identifies what a decibel value is for. The notations take the form of an italic capital letter and some subscript characters. The capital identifies the general type of value and the subscripts give specific details of what is being represented. Lxxx denotes a level (ie a value measured in dB by comparison with a reference value); Dxxx denotes a difference between two levels; Rxxx denotes a rating (or index), which is measure of the generalised acoustic performance of a material or construction based on a difference between two levels; Cxxx denotes a correction (or constant) Of these only those with L notations require a reference value statement.
Those with D or R notations are effectively ratios of two measured values not one measured value and a reference value and those with C notations are not based on reference values at all. A reference value statement therefore has no meaning when describing D, R and C decibels. Because decibels are logarithmic they have to be added, subtracted, multiplied, divided and averaged using different techniques from normal numbers.
Sound Pressure Level Lp obsolete – SPL This is the basic measure of how much sound there is at a given location. It is a measure of the size of the pressure fluctuations in the air that we perceive as sound. Sound Pressure Level is expressed in decibels with a reference level of 20 µPa (Lp in dB re 20 µPa) Sound Power Level LW obsolete – SWL This is the total amount of sound produced by a source. It cannot be measured directly but it can be calculated from Sound Pressure Level measurements in known conditions. It can be used to predict the Sound Pressure Level at any point.
Sound Power Level is expressed in decibels with a reference level of 1 pW (LW in dB re 1 pW).
In the US a reference of 100 fW is sometimes used
AECOM Noise Ingress Assessment 12 Capabilities on project: Building Engineering Pitch, frequency tonal sound broadband sound impulsive sound frequency analysis The sound we perceive can have different characteristics. These can range from low-pitched hums to high-pitched squeals and impulsive sounds. In engineering acoustics the word frequency rather than pitch tends to be used when describing the characteristics of a sound. The unit of frequency is the Hertz (Hz), which is the number of pressure fluctuations per second.
Any sound can be defined by its frequency content. Some sounds comprise just one discrete frequency (tonal sounds).
Others are distributed over wide frequency ranges (broad band sound). Impulsive sounds are made up short pulses of high frequency components. Sources often produce all of these types of sound at the same time. There are different ways of analysing and displaying the frequency content of a sound: Octave Band Analysis is the simplest method. The audible range of frequencies is divided into 10 bands.
Third-Octave Band Analysis more detailed with 30 bands Narrow Band Analysis 12th Octave (120 bands), 24th Octave (240), Fast Fourier (FFT) Analysis a high resolution technique that can give extremely detailed information on frequency content A-weighting LA or LpA, LWA, obsolete – dBA, dB(A) similar – C-weighting LC or LpC, LWC The human ear does not sense all frequencies of sound equally. Our sensitivity is at a maximum at around 2 kHz and steadily decreases above and below. Below 20 Hz and above about 20 kHz we can’t hear at all.
Within its operating limits a precision measurement microphone measures all frequencies the same so the output it produces does not reflect what we would actually hear.
The A-weighting is an electronic filter that matches the response of a sound level meter to that of the human ear. When A-weighted the Sound Pressure Level Lp becomes LpA (or LA) and the Sound Power Level LW becomes LWA. It used to be common to identify that a level was A-weighted by writing dB(A) or dBA instead of dB. These terms are now obsolete and should not be used as they conflict with other, nonacoustic, uses of decibels The response of the human ear varies depending on how loud the sound is. A-weighting matches the response of a sound level meter to human hearing at low levels (~ 40-90 dB).
For higher levels there are other weightings the most common of which is the C-weighting. Noise Rating NR similar – NC Sounds of different frequencies behave differently when they reflect from surfaces, pass through partitions or deflect over barriers. These varying properties have to be considered when making acoustic design decisions.
It is therefore sometimes appropriate, when specifying noise levels, to define limits in octave bands rather than just an overall A-weighted level. Sometimes specifications for individual octave bands are derived specifically for a given situation. In other situations it is appropriate to use a standard set of octave band limits such as the Noise Rating Curves. The Noise Rating for a measured sound spectrum is obtained by plotting the un-weighted octave band levels on a set of NR curves. The NR value is the highest curve that is crossed by any one octave band.
Noise Criterion (NC) curves are based on a similar principle but the curves are a slightly different shape.
At low frequencies NC curves are lower in level than the equivalent NR curves. Different types of decibels commonly used in acoustics
AECOM Noise Ingress Assessment 13 Capabilities on project: Building Engineering Lp LpA (or LA) LAF, LAS The instantaneous sound pressure level (Lp) The A-weighted instantaneous sound pressure level (LpA or LA) This is the root mean square size of the pressure fluctuations in the air. This level can fluctuate wildly even for seemingly steady sounds. To make sound level meters easier to read the values on the display are smoothed or damped out. This is effectively done by taking a rolling average of the previous 0.125 s (FAST time constant) or the previous 1 s (SLOW time constant).
The letters F or S are added to the subscripts in the notation to indicate when the FAST or SLOW time constant has been used.
These are often omitted but it is good practice to include them. Lmax LAmax LAFmax Lmin , LFmin The maximum instantaneous sound pressure level (Lmax), The A-weighted maximum instantaneous sound pressure level (LAmax) The A-weighted maximum instantaneous sound pressure level with a FAST time constant (LAFmax). This is the highest instantaneous sound pressure level reached during a measurement period.
The opposite of the Lmax is the minimum instantaneous sound pressure level or Lmin etc. It is good practice to include the letter which identifies the time constant used as this can make a significant difference to the value. Lpeak LApeak , LCpeak The peak sound pressure level (Lpeak) The A (or C)-weighted peak sound pressure level (LApeak or LCpeak) This is the size of the single largest pressure fluctuation during a measurement. It is different from the LAmax as it is not based on the RMS value. This value is sometimes quoted as a peak acoustic pressure in Pascals rather than a peak sound pressure level in dB re 20 µPa.
LN,T LAN,T LAFN,T N = %age value, 0-100 T = measurement time eg. LA90, LA10, LAF90, 5 min The percentage exceedence sound pressure level (LN,T), The A-weighted percentage exceedence sound pressure level (LAN,T), the A-weighted percentage exceedence sound pressure level with a FAST time constant (LAFN,T). This is the sound pressure level exceeded for N% of time period T. eg. If an Aweighted level of x dB is exceeded for a total of 6 minutes within one hour, the level will have been above x dB for 10% of the measurement period. This is written as LA10,1hr = x dB.
LA0 (the level exceeded for 0 % of the time) is equivalent to the LAmax and LA100 (the level exceeded for 100 % of the time) is equivalent to the LAmin. It is good practice to include the letter which identifies the time constant used as this can make a significant difference to the value. Leq,T LAeq,T T = measurement time eg. LAeq,5min The equivalent continuous sound pressure level over period T (Leq,T), The A-weighted equivalent continuous sound pressure level over period T (LAeq,T). This is effectively the average sound pressure level over a given period. As the decibel is a logarithmic quantity the Leq is not a simple arithmetic mean value.
The Leq is calculated from the raw sound pressure data. It is not appropriate to include a reference to the FAST and SLOW time constants in the notation
AECOM Noise Ingress Assessment 14 Capabilities on project: Building Engineering R The sound reduction index This a measure of the sound insulation performance a material or construction measured under laboratory conditions in accordance with BS EN ISO 140-3. R differs from D in that it takes account of the area of the construction under test as well as the absorption in the receiving room, both of these factors influence the measured D. Taking into account these factors allows the R for different constructions to be compared on a like for like basis. R values are quoted in third-octaves between ?? Hz and ?? Hz Rw The weighted sound reduction index A single value of the R derived from the third octave values of R using the method described in BS EN ISO 717-1.
Partitioning and building board manufacturers commonly use this index to describe the inherent sound insulation performance of their products.
Dne The normalised level difference of a building element This is a measure of the acoustic performance of a discrete building element or such as a trickle ventilator. The level difference is established within a laboratory and normalised to a reference area of absorption which is 10m 2 .