Classroom acoustics: How to combat noisy learning environments.

An environment where good communication can take place should be a goal for any classroom.

Excessive noise in schools has been shown to have a detrimental impact on student learning and performance. So why is classroom acoustics not yet a prime consideration in the design of new classroom facilities in Australia? The Building Code of Australia (BCA) details only minimum standards for buildings, but no specific recommendations for educational facilities.

The AS/NZS2107:2000 standard recommends levels for ambient noise and reverberation times in unoccupied classrooms, however no recommendations are made for occupied classroom conditions.

There are no other regulations or standards, Australia wide, that covers all aspects of acoustical qualities in educational facilities.

How do you go about controlling sound without guidelines?

You start with two very basic control measures:

1)        Reduce reverberation -use materials with high noise reduction coefficient (NRC). 

Reverberations occur when sound waves strike surfaces in a room, like floors, walls, and ceilings, and are reflected back into the space. Reverberation will continue until all the sound waves have been absorbed or have dissipated.  Excessive reverberation can cause echoes that interfere with speech intelligibility.

The most common measure of acoustic reverberation performance is NRC. NRC refers to a surface’s ability to reduce noise by absorbing sound.  NRC ranges from 0 (total reflection) to 1.00 (total absorption).

2)        Reduce sound transmission – use materials with high Ceiling attenuation class (CAC). Open-plan classrooms and classrooms with thin partition walls between instruction areas are problematic as sound transmission between the rooms are not blocked.

(CAC indicates the ability of a ceiling to block airborne sound transmission between adjacent rooms, especially when the dividing wall does not connect with the structural ceiling. A ceiling panel with a CAC of 40 will reduce transmitted sound by 40 decibels. A ceiling panel with a CAC of 35 or higher offers significant sound attenuation properties.

An acoustical unit with a high CAC (sound blockage) may have a low NRC (sound absorption).

Other points to consider when selecting an acoustic product

Who carries out the testing for NRC or CAC?

Ensure that testing has been carried out by a NATA-accredited aboratory.  NATA (National Association of Testing Authorities) accreditation reflects a high level of competence, credibility, independence and integrity to the accredited facility.

Where is the product from? Can you guarantee the quality of your product?

There have been many reports in the past of building materials being imported to Australia, without meeting Australian standards. Beware that you are not buying an inferior product.

Consider products that are lighter in weight, with improved acoustic performance.

In the past, heavier products offered greater acoustic properties. Advances in technology now provide a myriad of products that are much lighter and have improved acoustic performance. It is much more cost effective to install a lighter weight product because more lightweight structural   supports can now be used.

Is the product resistant to the local climate/environment? 

Past experience has shown that certain products installed in humid conditions may sag as a result of moisture absorption. Some might even be prone to mould causing all sorts of hygiene issues. Be selective in the materials you choose. Ensure that they not only have high acoustic properties, but also applicable to local conditions.


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