School and Educational Acoustics – Acoustic Design

A Manchester primary school appointed Dragonfly Acoustics to carry out an assessment of the noise environment within the school hall.

The aim of the assessment was to establish whether this environment was suitable for its current use as a school assembly space and what steps could be taken to improve the acoustic performance for that purpose. The noise assessment was conducted broadly in accordance with ISO 3382-2 (2008) Measurement of room acoustic parameters – Part 2: Reverberation time in ordinary rooms.

Measurements of reverberation time were undertaken at various points throughout the asembly hall and this data was used to build up a picture of the acoustic environment within the room. Comparisons were then made between this data and the reverberation time criteria for an assembly hall as detailed within Building Bulletin 93 (BB93) of the Building Regulations 2000.

The assessment showed that an increase in absorptive area of 60m2 with an absorption coefficient of at least 0.9 would be required to reduce the reverberation time in order to reduce the Tmf (middle frequency reverberation) to below 1.2 seconds as recommended by BB93.

Dragonfly Acoustics further recommended that reducing the break-in of external noise into the asembly hall would increase speech intelligibility within the hall. Noise break-in through the external facade could be reduced through the use of secondary glazing and this would have a significant impact on the quality of the noise environment within the assembly hall.

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