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SOUND INSULATION TESTS
Scope of Report
To factually present measured levels of sound insulation provided by a sample of partitions in a terrace of flats and houses at the rear of ...
1. INTRODUCTION
1.1 ... Building Contractors have recently completed construction of a terrace of flats and houses at ... .
1.2 They are required, by their client, to demonstrate compliance with the Building Regulations Approved Document E - Resistance to the passage of sound.
1.3 Civil Engineering Dynamics undertook sound insulation measurements of a sample of partitions in the building. This report details the results of that survey.
1.4 The survey was undertaken on Monday 25th September 00 between 11:00 and 18:00.
2. THE SITE
2.1 The building is a long terrace running NW - SE. The SE end is three 3-storey houses. The NW end is eight flats split on two floors. In-between the two are two 2-storey houses. An indicative elevation is shown in Figure 1.
2.2 All rooms are currently unfurnished and are yet to be carpeted.
2.3 Painting and decorating work was being undertaken in the building at the time of the survey. Bricklaying was being undertaken at the rear of the building at the time of the survey.
3. MEASUREMENT PROCEDURE
3.1 The measurements were performed using a Bruel & Kjaer 2260 Sound Level Analyser running BZ 7204 Building Acoustics Software, a JBL Eon 15 loudspeaker and a Bruel & Kjaer 3204 Tapping Machine.
3.2 The essence of the airborne sound insulation tests is to generate a loud broad band noise in one room, and then to compare noise measurements made in the room with measurements of the noise made in the room below. The room containing the loudspeaker is called the source room, the other room the receiving room. A broad band noise is one that has noise at a wide range of frequencies. These tests used a white noise signal, generated by the 2260 Analyser.
3.3 The measurements were repeated with the loudspeaker and sound level analyser at a number of locations to allow for the variation in sound pressure level within a room. The average of these measurements is used in the sound insulation calculations.
3.4 The impact sound tests measure the noise level in the receiving room due to repeated impacts from a standard tapping machine operating in the source room, as specified by BS 2750.
3.5 Each airborne sound test was performed twice, using each room as the source. The measurements were made using a 1/3rd-octave frequency resolution.
3.6 The results of the airborne sound tests were processed using the 2260 Analyser to determine the Standardised Level Difference, DnT (dB), and the Weighted Standardised Level Difference, DnTw (dB), in accordance with BS 2750:Part 4:1980. The Weighted Standardised Level Difference is a single number quantity derived from the 1/3rd octave band values of the Standardised Level Difference.
3.7 The results of the impact sound tests were processed using the 2260 Analyser to determine the Standardised Impact Sound Pressure Level, L'nT (dB), and the Weighted Standardised Impact Sound Pressure Level, L'nTw (dB), in accordance with BS 2750:Part 7:1980. The Weighted Standardised Impact Sound Pressure Level is a single number quantity derived from the 1/3rd octave band values of the Standardised Impact Sound Pressure Level.
3.8 The analysis also determines a Reference Curve from the 1/3rd octave band values of the Standardised Level Difference, in accordance with BS 5821:Part 1:1984, to assist in comparisons with the levels set by The Building Regulations. Deviations from the Reference Curve are also calculated.
3.9 Each wall or floor is referred to as a partition. The partitions are labelled for each direction of sound transmission. Figure 1 shows the labelling of partitions.
3.10 All tests are undertaken between rooms at the rear of the building. The rooms at the front of the flats are kitchens and bathrooms, and therefore there are no party walls between habitable rooms. Rooms at the front of the houses are separated by the staircase, and therefore there are no party walls between habitable rooms.
3.11 Please refer to the client's drawings for details of the floor plan.
3.12 Measurements are made of a sample of partitions. It is assumed that there is little variation between partitions of an identical design. It is noted that this survey will not detect unusual defects in partitions not tested, if there are any.
3.13 Background noise can affect the results of the measurement. If there is a high level of background noise, measurements in the receiver room are higher because they are not solely due to the loudspeaker in the source room, and therefore the calculated sound insulation values would be under estimated. Measurements of background noise are taken after each measurement in the receiving room to reduce the influence of background noise on the final calculation.
4. RESULTS
4.1 The Building Regulations Approved Document E sets a minimum value of Weighted Standardised Level Difference (DnT,w) for individual walls and floors, and a maximum value of Weighted Standardised Impact Sound Pressure Level (L'nT,w).
4.2 The weighted levels are derived from curve fitting a standard reference curve to the 1/3rd octave band frequency measurements of the parameter.
4.3 The requirements are listed in Table A.
TABLE A: Building Regulations Approved Document E, Minimum Requirements
Walls Floors Mean Value Individual Value Mean Value Individual Value Airborne Sound (DnT,w) dB. >= 53 >= 49 >= 52 >= 48 Impact Sound (L'nT,w) dB. n/a <= 62 <= 65
4.4 Figures 2 to 12 show the results as third octave spectra.
4.5 Measurement of Floors
4.5.1 Table B summarises the results of the tests of floors.
TABLE B: Results of Sound Insulation Tests of Floors
Partition DnT,w (dB) L’nT,w (dB) C 52 x D 53 60 S 51 59 T 51 x MEAN 52 60
4.6 Measurement of Walls
4.6.1 Table C summarises the tests undertaken of walls.
TABLE C: Results of Sound Insulation Tests of Walls
Partition DnT,w (dB) A 50 B 50 E 61 F 60 G 56 H 58 I 56 J 56 M 56 N 55 O 55 P 54 Q 52 R 51 MEAN 55
4.6.2 Measurement Partition K/L measures the airborne sound insulation between the rear first floor room of the most SE 2-storey house and the rear second floor room of the adjacent 3-storey house. It investigates transmission paths through the roof space.
4.6.3 The results of Partition K/L are DnT,w = 62 dB.
4.6.4 Deviations from the reference curve for each partition are shown in Table D.
TABLE D: Deviations from the Reference Curve
Partition 1/3rd Octave Centre Frequency (Hz) 100 125 160 200 250 315 400 500 630 800 1k 1.25k 1.6k 2k 2.5k 3.15k A -2.2 -4.9 -4.2 -3.3 + + -0.8 -4.4 -4.6 -0.9 + + -0.9 -1.1 + + B -5.1 -4.9 + + -0.8 -1.4 -1.5 -1.7 -5.4 -0.4 + + -1.2 -3.1 + + C -7 -7.4 -8.1 -5 -1.5 + + + + + + + + + + + D -6.6 -10.6 -5.4 -5.7 -2.2 -1.5 + + + + + + + + + + E -0.8 + -6.2 -4.8 -2.2 -6 -5.1 -1.1 -1.3 -1.3 + + + -0.1 + + F -7.8 -2.5 -2.2 -3.1 -2.4 -1.4 -3.2 -0.6 -1 -0.3 + + + + + + G -3.4 -3.9 -5.3 -11.9 -5.5 -2 + + + + + + + + + + H -2 -4.1 -8.4 -5.9 -5 -2.4 -2.4 -1.1 + + + + + + + + I -2.3 -3.6 -1.3 + -1.8 -2 -2.3 -1.6 -0.6 -2.1 -2.5 -2.6 -2 + -0.1 -0.1 J -6.7 + -0.5 -0.5 -0.4 -1.4 -0.4 -1.1 -2.1 -3.2 -2.6 -2.2 -2.4 -0.9 + + K -10.4 -7.9 -0.3 -5 -2.1 + + + + + + + + + + + L -7.2 -4.1 -2.8 -2.7 -1 -0.7 -1.1 -0.6 + -1.5 -2.3 -2.3 -3.2 + + + M -1.7 -1.8 -9.9 -7.2 -1.8 -5 -2.9 + + + -0.1 + + + + + N -4.8 -5.4 -7.1 -5.1 -2.9 -0.2 + + + + + + + + + + O -7 -2.8 -3.2 -6.2 -4.8 -2.6 -1.2 -1.1 -0.6 -0.4 -0.4 + + + + + P -5.3 -5.8 -4.8 -3.8 -4.1 -4.4 -3 -0.1 + + + + + + + + Q -4.9 -1.2 -2.6 -4.1 -1.7 -3.7 -3.5 -5.1 -3.8 -1.3 + + + + + + R -7 + + -2.2 -2.2 -0.3 -5.1 -7.1 -2.1 + + + + + + + S -6 -6.1 -7.5 -5.3 -2.2 + + + + + + + + + + + S* + + + + -0.7 -7.5 -14 -22.3 -31.2 -35.6 -33.6 -27.8 -26.5 -22.8 -18.1 -17.8 T -4.3 -9.9 -7 -9.2 -1.5 + + + + + + + + + + + * Impact Sound Test
5. CONCLUSIONS
5.1 All the wall partitions tested meet the requirements for airborne sound insulation stated in Table 2 of the Building Regulations Approved Document E - 'Resistance to the Passage of Sound'.
5.2 All the floor partitions tested meet the requirements for airborne sound insulation stated in Table 2 of the Building Regulations Approved Document E - 'Resistance to the Passage of Sound'.
5.3 All the floor partitions tested meet the requirements for impact sound insulation stated in Table 2 of the Building Regulations Approved Document E - 'Resistance to the Passage of Sound'.
5.4 We note that some of the tests show large deviations from the Reference Curve at low frequencies. Where this occurs in only one direction through a partition, it may be attributed to contamination by external noises such as building work or train pass-by. Although every attempt was made to avoid taking measurements during any part of train pass-by or when other workers on site are generating noise, some contamination is inevitable.
5.5 It is noted that the rooms were tested in an unfurnished and uncarpeted state. The sound insulation provided by the partitions may be expected to increase after the rooms are carpeted and furnished.
6. REFERENCES:
6.1 BS 2750:Part 4:1980 'Methods of measurement of sound insulation in buildings and of building elements. Part 4. Field measurements of airborne sound insulation between rooms'.
6.2 BS 2750:Part 7:1980 'Methods of measurement of sound insulation in buildings and of building elements. Part 7. Field measurements of impact sound insulation between rooms'.
6.3 BS 5821:Part 1:1984 'Rating the sound insulation in buildings and of building elements. Part 1. Method for rating the airborne sound insulation in buildings and of interior building elements'.
6.4 BS 5821:Part 2:1984 'Rating the sound insulation in buildings and of building elements. Part 2. Method for rating the impact sound insulation in buildings and of interior building elements'.
6.5 The Building Regulations, 1991. Approved Document E -Resistance to the passage of sound. E2, Airborne sound (floors and stairs). E3, Impact sound (floors and stairs).- The Department of the Environment and The Welsh Office. 1992 Edition.