The BCA contains no specific acoustic provisions for Class 9b buildings but good acoustics are essential for the comfort of students and staff as well as effective learning and need to be taken into design considerations.
Gyprock acoustic wall and ceiling systems provide architects and designers with alternatives for noise situations in education facilities. The more common systems are outlined in the Gyprock Education Design Guide with a much wider selection available through the online System Selector and The Gyprock Red Book.
Gyprock manufactures a variety of plasterboards that are designed with a higher level of acoustic properties than standard plasterboard:
These plasterboards are recommended by Gyprock in wall and ceiling systems to meet functional needs and acoustic compliance requirements for school buildings including:
- Libraries and study rooms
- Staffrooms and common rooms
- Auditoriums and gymnasiums
- Service shafts and plant rooms
- Acoustic bulkheads
Acoustic design considerations for educaion facilities are summarised below. More complete recommendations including Gyprock wall and ceiling systems are outlined in the Gyprock Education Design Guide.
Education Acoustic Wall and Ceiling Design
Good acoustic design includes consideration of both noise entering the building or the transfer of sound within the building to affect students and staff and disrupt teaching.
- External noise entering through windows and external walls
- Rain noise on the roof transferred through the ceiling
- Noise travelling via junctions at walls and ceilings, i.e. flanking noise
- Noise from plant rooms being transferred through internal walls and ceilings
- Noise from mechanical equipment such as the HVAC system
Building systems and construction methods can vary greatly from site to site. Where acoustic performance is important, an acoustic engineer should be consulted to assess the suitability of all systems.
Weighted Sound Reduction Index Rw represents the reduction in sound from one side of an element to the other as a measure of direct sound transmission. Although it is not accurate for all frequencies, it is a good way of comparing systems, with higher numbers representing better performance.
For education facilities, wall systems should be selected according to the degree of sound transfer reduction required and by the amount of noise expected from surrounding areas.
In most rooms, comfortable acoustics depends directly on a short reverberation time. A sound in a room is still audible a short time after the source has ceased, due to reflection from the room's surfaces. Room volume, room shape, the amount of sound absorbing material and sound field diffuseness determine the reverberation time. The total amount of sound absorption in a room and hence the reverberation time, is critically important for speech intelligibility, privacy and sound levels, among other things.
When it comes to minimising sound disturbance between people in open areas, the layout is very important. Speech can be the most disturbing factor because it is very difficult to 'tune out'. However, in some open areas individuals must be given as much privacy as possible, for example, study areas. In order to prevent sound from being reflected and propagated via the ceiling, it is crucial that the acoustic ceiling has excellent sound absorption properties across the whole frequency range.
Rooms intended for conversation, or where a high degree of privacy is required, are most dependent on short reverberation times. These may be dining rooms, TV and games rooms, reading areas etc. The easiest and most cost effective way to achieve an effective acoustic environment is to install an acoustic ceiling that provides high sound absorption.
A material's sound absorbing properties are expressed by the sound absorption coefficient, NRC, which ranges from 0 (total reflection) to 1.00 (total absorption).
Services including HVAC, water supply and waste water can add significantly to the ambient sound level. Care must be taken to ensure that fixed ductwork is adequately insulated internally down stream of fan units and that pipes are lagged or enclosed in rated cavities.