REVERBERATION (FLATS OR ROOMS FOR RESIDENTIAL PURPOSES)

Table 7.2: Example calculation for an entrance hall (Method B)

Step 1 Calculate the surface area related to each absorptive material (i.e. for the floor, walls, doors and ceiling).

Step 2 Obtain values of absorption coefficients for the carpet, painted concrete block walls and the timber doors. In this case, the values are taken from Table 7.1.

Step 3 Calculate the absorption area (m2) related to each absorptive surface (i.e. for the floor, walls and doors) in octave frequency bands (Absorption area = surface area x absorption coefficient).

Step 4 Calculate the sum of the absorption areas (m2) obtained in step 3

Step 5 Calculate the total absorption area (AT) required for the entrance hall. The volume is 30 m3 and therefore 0.2 x 30.0 = 6.0 m2 of absorption area is required.

Step 6 Calculate additional absorption area (A) to be provided by ceiling (m2). If any values of minimum absorption area are negative, e.g. see 2000 Hz and 4000 Hz, then there is sufficient absorption from the other surfaces to meet the requirement without any additional absorption in this octave band. (Additional absorption = AT – total absorption area (from Step 5))

Step 7 Calculate required absorption coefficient (a) to be provided by ceiling (Required absorption coefficient = Additional absorption area / area of ceiling)

Step 8 Identify a ceiling product from manufacturer’s laboratory measurement data that provides absorption coefficients that exceed the values calculated in step 7.

Resistance to the passage of sound 67

ACOUSTIC CONDITIONS IN SCHOOLS SOUNDPROOFING

Section 8: Acoustic conditions in schools

8.1 In the Secretary of State’s view the normal way of satisfying Requirement E4 will be to meet the values for sound insulation, reverberation time and internal ambient noise which are given in Section 1 of Building Bulletin 93 ‘The Acoustic Design of Schools’, produced by DfES and published by the Stationery Office (ISBN: 0 11 271105 7) (to be published during 2003).

METHOD FOR CALCULATING MASS PER UNIT AREA

Annex A: Method for calculating mass per unit area

A1 Wall mass

A1.1 Where a mass is specified it is expressed as mass per unit area in kilograms per square metre (kg/m2).

A1.2 The mass may be obtained from the manufacturer or it may be calculated by the method given in this annex. To calculate the mass per unit area of a masonry leaf use the formula below. This formula is not exact but is sufficient for this purpose.

A2 Formula for calculation of wall leaf mass per unit area.

A2.1 Mass per unit area of a brick/block leaf = mass of co-ordinating area / co-ordinating area

M_B + p_m (Td (L + H - d) +V) = kg/m 2
LH

where

M_B is brick/block mass (kg) at appropriate moisture content

p_m is density of mortar (kg/m3) at appropriate moisture content

T is the brick/block thickness without surface finish (m)

d is mortar thickness (m)

L is co-ordinating length (m)

H is co-ordinating height (m) V is volume of any frog/void filled with mortar (m3)

Note: This formula provides the mass per unit area of the block/brick construction without surface finish.

Note: See Diagram A.1 for block and mortar dimensions.

A2.2 When calculating the mass per unit area for bricks and blocks use the density at the appropriate moisture content from Table 3.2, CIBSE Guide A (1999).

A2.3 For cavity walls the mass per unit area of each leaf is calculated and added together.

A2.4 Where surface finishes are used the mass per unit area of the finish is added to the mass per unit area of the wall.

Diagram A-1: Block and mortar dimensions

A3.1 Two examples are given (see Table A.1 and A.2) using the equation in A2.1. For each of these examples a simplified equation is obtained for that type of construction.

Table A.1 Blocks laid flat

Example of single leaf wall, blocks laid flat d = 0.010 m T = 0.215 m L = 0.450 m H = 0.110 m V = 0 m3 pm = 1800 kg/m3

No surface finish

Mass per unit area = 20.2MB + 43.0 kg/m2

Substituting for MB in this formula gives the following values: Block mass, MB (kg) Mass per unit area (kg/m2)

6 164 8 205 10 245 12 285 14 326 16 366 18 407

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E METHOD FOR CALCULATING MASS PER UNIT AREA

Table A.2: Blocks laid on edge Example of single leaf wall, blocks laid on edge d = 0.010 m T = 0.100 m L = 0.450 m H = 0.225 m V = 0 m3 pm = 1800 kg/m3 No surface finish Single leaf wall: Mass per unit area = 9.9MB + 11.8 kg/m2 Cavity wall: Mass per unit area = 19.8MB + 23.6 kg/m2 Substituting for MB in this formula gives the following values: Block mass, MB (kg) Mass per unit area (kg/m2) Single leaf Cavity 6 71 142 8 91 182 10 111 222 12 131 261 14 150 301 16 170 340 18 190 380 A4 Mass per unit area of surface finishes

A4.1 The mass per unit area of surface finishes should be obtained from manufacturer’s data. A5 Mass per unit area of floors A5.1 The mass of a solid and homogeneous floor (without hollows, beams or ribs) can be calculated from:

MF= cx T where,

Diagram A-2: Beam and block floor dimensions

A5.3 For other floor types (including floors with variable thickness), seek advice from the manufacturer on mass per unit area and performance.

MF is mass per unit area of floor (kg/m2) pc is density of concrete (kg/m3) T is thickness of floor (m)

A5.2 The mass of a beam and block floor can be calculated from:

MF = (Mbeam,1m + Mblock,1m) / LB where

MF is mass per unit area of floor (kg/m2) Mbeam,1m is the mass of a 1 m length of beam (kg) Mblock,1m is the mass of a 1 m length of blocks (kg)

LB is the distance between the beam centre lines, i.e. the repetition interval (m) Note: See Diagram A.2 for beam and block floor dimensions.

Resistance to the passage of sound 70

PROCEDURES FOR SOUND INSULATION TESTING

Annex B: Procedures for sound insulation testing

B1 Introduction

B1.1 Section B.2 of this Annex describes the sound insulation testing procedure approved by the Secretary of State for the purposes of Regulation 20A (2)(a) of the Building Regulations and Regulation 12A (2)(a) of the Approved Inspectors Regulations. The approved procedure is that set out in Section B.2 and the Standards referred to in that Section.

B1.2 Section B.3 of this Annex provides guidance on laboratory testing in connection with achieving compliance with Requirement E2 in Schedule 1 to the Building Regulations, and in connection with evaluation of components to be used in constructions subject to Requirement E1.

B1.3 Section B.4 of this Annex gives guidance on test reports.

B1.4 The person carrying out the building work should arrange for sound insulation testing to be carried out by a test body with appropriate third party accreditation. Test bodies conducting testing should preferably have UKAS accreditation (or a European equivalent) for field measurements. The measurement instrumentation used should have a valid, traceable certificate of calibration, and should have been tested within the past two years.

B2 Field measurement of sound insulation of separating walls and floors for the purposes of Regulation 20A and Regulation 12A Introduction

B2.1 Sound insulation testing for the purposes of Regulation 20A of the Building Regulations and Regulation 12A of the Approved Inspectors Regulations 2000, must be done in accordance with: BS EN ISO 140-4:1998; BS EN ISO 140- 7:1998; BS EN ISO 717-1:1997; BS EN ISO 717-2:1997; BS EN 20354:1993. When calculating sound insulation test results, no rounding should occur in any calculation until required by the relevant Standards, the BS EN ISO 140 series and the BS EN ISO 717 series.

Airborne sound insulation of a separating wall or floor

B2.2 The airborne sound insulation of a separating wall or floor should be measured in accordance with BS EN ISO 140-4:1998. All measurements and calculations should be carried out using one-third-octave frequency bands. Performance should be rated in terms of the weighted standardized level difference,

DnT,w, and spectrum adaptation term, Ctr, in accordance with BS EN ISO 717-1:1997.

Measurements using a single sound source

B2.3 For each source position, the average sound pressure level in the source and receiving rooms is measured in one-third-octave bands using either fixed microphone positions (and averaging these values on an energy basis), or using a moving microphone.

B2.4 For the source room measurements, the difference between the average sound pressure levels in adjacent one-third-octave bands should be no more than 6 dB. If this condition is not met, the source spectrum should be adjusted and the source room measurement repeated. If the condition is met, the average sound pressure level in the receiving room, and hence a level difference, should be determined.

B2.5 It is essential that all measurements made in the source and receiving rooms to determine a level difference should be made without moving the sound source or changing the output level of the sound source, once its spectrum has been correctly adjusted (where necessary).

B2.6 The sound source should now be moved to the next position in the source room and the above procedure repeated to determine another level difference. At least two positions should be used for the source. The level differences obtained from each source position should be arithmetically averaged to determine the level difference, D as defined in BS EN ISO 140-4:1998.

Measurements using multiple sound sources operating simultaneously

B2.7 For multiple sound sources operating simultaneously, the average sound pressure level in the source and receiving rooms is measured in one-third-octave bands using either fixed microphone positions (and averaging these values on an energy basis), or using a moving microphone.

B2.8 For the source room measurements, the difference between the average sound pressure levels in adjacent one-third-octave bands should be no more than 6 dB. If this condition is not met, the source spectrum should be adjusted and the source room measurement repeated. If the condition is met, determine the average level in the receiving room, and hence the level difference, D as defined in BS EN ISO 140-4:1998.

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E PROCEDURES FOR SOUND INSULATION TESTING

Impact sound transmission of a separating floor

B2.9 The impact sound transmission of a separating floor should be measured in accordance with BS EN ISO 140-7:1998. All measurements and calculations should be carried out using one-third-octave frequency bands. Performance should be rated in terms of the weighted standardized impact sound pressure level, L’nT,w in accordance with BS EN ISO 717-2:1997.

Measurement of reverberation time

B2.10 BS EN ISO 140-4:1998 and BS EN ISO 140-7:1998 refer to the

ISO 354 (BS EN 20354:1993) method for measuring reverberation time. However for the approved procedure, the guidance in

BS EN ISO 140-7:1998 relating to the source and microphone positions, and the number of decay measurements required, should be followed.

Room requirements

B2.11 Section 1 gives guidance on the room types that should be used for testing. These rooms should have volumes of at least 25 m3. If this is not possible then the volumes of the rooms used for testing should be reported.

Tests between rooms

B2.12 Tests should be conducted in completed but unfurnished rooms or available spaces in the case of properties sold before fitting out; see Section 1.

B2.13 Impact sound insulation tests should be conducted on a floor without a soft covering (e.g. carpet, foam backed vinyl etc) except in the case of (a) separating floor type 1, as described in this Approved Document, or (b) a concrete structural floor base which has a soft covering as an integral part of the floor.

B2.14 If a soft covering has been installed on any other type of floor, it should be taken up. If that is not possible, at least half of the floor should be exposed and the tapping machine should be placed only on the exposed part of the floor.

B2.15 When measuring airborne sound insulation between a pair of rooms of unequal volume, the sound source should be in the larger room.

B2.16 Doors and windows should be closed.

B2.17 Kitchen units, cupboards etc. on all walls should have their doors open and be unfilled.

Measurement precision

B2.18 Sound pressure levels should be measured to 0.1 dB precision.

B2.19 Reverberation times should be measured to 0.01 s precision.

Measurements using a moving microphone B2.20 At least two positions should be used.

B2.21 For measurements of reverberation time, discrete positions should be used rather than a moving microphone.

B3 Laboratory measurements

Introduction

B3.1 Pre-completion testing for the purposes of Regulation 20A and Regulation 12A involves field testing on separating walls and floors (see Section 1 and Annex B: B2). However, there are applications for laboratory tests to determine

the performance of: floor coverings; floating floors; wall ties; resilient layers; internal walls and floors; and flanking laboratory tests to indicate the performance of novel constructions.

B3.2 When calculating sound insulation test results, no rounding should occur in any calculation until required by the relevant Standards, i.e. the BS EN ISO 140 series and the BS EN ISO 717 series.

Tests on floor coverings and floating floors

B3.3 Floor coverings and floating floors should be tested in accordance with

BS EN ISO 140-8:1998 and rated in accordance with BS EN ISO 717-2:1997. The test floor should have a thickness of 140 mm.

B3.4 It should be noted that text has been omitted from BS EN ISO 140-8:1998. For the purposes of this Approved Document, section 6.2.1 of BS EN ISO 140-8:1998 should be disregarded, and section 5.3.3 of BS EN ISO 140-7:1998, respectively, referred to instead.

B3.5 BS EN ISO 140-8:1998 refers to the ISO 354 (BS EN 20354:1993) method for measuring reverberation time, but the guidance in BS EN ISO 140-8:1998 relating to the source and microphone positions, and the number of decay measurements required, should be followed.

B3.6 When assessing category II test specimens (as defined in BS EN ISO 140-8:1998) for use with separating floor type 2, the performance value (ALw) should be achieved when the floating floor is both loaded and unloaded. The loaded measurements should use a uniformly distributed load of 20-25 kg/m2 with at least one weight per square metre of the flooring area, as described in BS EN ISO 140-8:1998. Dynamic stiffness of resilient layers

B3.7 Dynamic stiffness of resilient layers should be measured in accordance with

BS EN 29052-1:1992. The test method using sinusoidal signals should be used. No pre-compression should be applied to the test specimens before the measurements.

Resistance to the passage of sound 72 Approved Document E

PROCEDURES FOR SOUND INSULATION TESTING

Dynamic stiffness of wall ties

B3.8 Dynamic stiffness of wall ties should be measured in accordance with BRE Information Paper I P 3/01. Airborne sound insulation of internal wall and floor elements

B3.9 The airborne sound insulation of internal wall or floor elements in a laboratory should be measured in accordance with BS EN ISO 140-3:1995, and the performance rated in accordance with BS EN ISO 717-1:1997 to determine the weighted sound reduction index, Rw.

Measurements in a flanking laboratory

B3.10 Tests of sound transmission in a flanking laboratory include both direct and flanking paths, and are a useful means of assessing the likely field performance of novel constructions.

B3.11 It is not possible to demonstrate compliance with Requirement E1 using test results from a flanking laboratory.

Flanking laboratory: Design

B3.12 Construction details of a suitable laboratory can be obtained from the Acoustics Centre, BRE, Garston, Watford WD25 9XX.

Note: A CEN standard for the laboratory measurement of flanking transmission between adjoining rooms is currently under development.

Flanking laboratory: Indicative airborne sound insulation values

B3.13 When a test construction has airborne

sound insulation of at least 49 dB DnT,w + Ctr

when measured in a flanking laboratory using the procedure given in Annex B: B2, this can be taken as indicative that the same construction (i.e. identical in all significant

details) may achieve at least 45 dB DnT,w + Ctr when built in the field. See paragraph B3.11.

Flanking laboratory: Indicative impact sound insulation values

B3.14 When a test construction has impact sound insulation no more than 58 dB L’nT,w when measured in a flanking laboratory using the procedure given in Annex B: B2, this can be taken as indicative that the same construction (i.e. identical in all significant details) may achieve no more than 62 dB L’nT,w when built in the field. See paragraph B3.11.

B4 Information to be included in test reports

Field test reports

B4.1 Paragraph 1.41 of this Approved Document sets out the manner of recording the results of testing done for the purposes of Regulation 20A or Regulation 12A, approved by the Secretary of State under those Regulations. Although not required, it may be useful to have a description of the building including:

1. sketches showing the layout and dimensions of rooms tested;
2. description of separating walls, external walls, separating floors, and internal walls and floors including details of materials used for their construction and finishes;
3. mass per unit area in kg/m2 of separating walls, external walls, separating floors, and internal walls and floors;
4. dimensions of any step and/or stagger between rooms tested;
5. dimensions and position of any windows or doors in external walls.

Laboratory test reports for internal walls and floors

B4.2 Test reports should include the following information.

1. Organisation conducting test, including:
   1. name and address;
   2. third party accreditation number (e.g. UKAS or European equivalent);
   3. Name(s) of person(s) in charge of test.
2. Name(s) of client(s).
3. Date of test.
4. Brief details of test, including:
   1. equipment;
   2. test procedures.
5. Full details of the construction under test and the mounting conditions.
6. Results of test shown in tabular and graphical form for third octave bands according to the relevant part of the BS EN ISO 140 series and BS EN ISO 717 series, including:
   1. single-number quantity and the spectrum adaptation terms;
   2. data from which the single-number quantity is calculated.

Approved Document E Resistance to the passage of sound 73

E GLOSSARY

Annex C: Glossary

The definitions given below are for the purposes of this document only, and are not intended to be rigorous. Fuller definitions of the various acoustical terms are to be found in the relevant British Standards listed in Annex D.

Absorption Conversion of sound energy to heat, often by the use of a porous material.

Absorption coefficient A quantity characterizing the effectiveness of a sound absorbing surface. The proportion of sound energy absorbed is given as a number between zero (for a fully reflective surface) and one (for a fully absorptive surface). Note that sound absorption coefficients determined from laboratory measurements may have values slightly larger than one. See BS EN 20354:1993.

Absorptive material Material that absorbs sound energy. Airborne sound Sound propagating through the air. Airborne sound insulation Sound insulation that reduces transmission of airborne sound between buildings or parts of buildings. Air path A direct or indirect air passage from one side of a structure to the other. Caulking Process of sealing joints. Cavity stop A proprietary product or material such as mineral wool used to close the gap in a cavity wall. Ctr The correction to a sound insulation quantity (such as DnT,w) to take account of a specific sound spectra. See BS EN ISO 717-1:1997. dB (See decibel) Decibel (dB) The unit used for many acoustic quantities to indicate the level with respect to a reference level. Density Mass per unit volume, expressed in kilograms per cubic metre (kg/m3). Direct transmission The process in which sound that is incident on one side of a building element is radiated by the other side. DnT The difference in sound level between a pair of rooms, in a stated frequency band, corrected for the reverberation time. See BS EN ISO 140-4:1998. DnT,w A single-number quantity which characterizes the airborne sound insulation between rooms. See BS EN ISO 717-1:1997. DnT,w + Ctr A single-number quantity which characterizes the airborne sound insulation between rooms using noise spectrum no. 2 as defined in BS EN ISO 717-1:1997. See BS EN ISO 717-1:1997. Dynamic stiffness A parameter used to describe the ability of a resilient material or wall tie to transmit vibration. Specimens with high dynamic stiffness (dynamically ‘stiff’) transmit more vibration than specimens with low dynamic stiffness (dynamically ‘soft’). See BS EN 29052-1:1992 for resilient materials. See BRE Information Paper IP 3/01 for wall ties. Flanking element Any building element that contributes to sound transmission between rooms in a building that is not a separating floor or separating wall. Flanking transmission Sound transmitted between rooms via flanking elements instead of directly through separating elements or along any path other than the direct path. Floating floor A floating floor consists of a floating layer and resilient layer (see also resilient layer and floating layer). Floating layer A surface layer that rests on a resilient layer and is therefore isolated from the base floor and the surrounding walls (see also resilient layer). Framed wall A partition consisting of board or boards connected to both sides of a wood or metal frame. Frequency The number of pressure variations (or cycles) per second that gives a sound its distinctive tone. The unit of frequency is the Hertz (Hz). Frequency band A continuous range of frequencies between stated upper and lower limits, (see also octave band and one-third-octave band). Hertz (Hz) The unit of the frequency of a sound (formerly called cycles per second). Resistance to the passage of sound 74 Approved Document E