Ecophon Acoustic Bulletin

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Thank you for sharing this report.

I am delighted but not surprised by the large benefits achieved by reverberation reduction in preschool classrooms.

It is important that significant noise reduction beyond that expected by the Sabine equation can be obtained by installing highly effective acoustical ceilings in preschool classrooms.

This effect has long been observed; for example, in noisy restaurants. But it was first reported for preschools in our 2002 paper to the Acoustical Society of America:

The role of soundscape in children’s learning (David Lubman and Louis C. Sutherland); J. Acoust. Soc. Am. 112 (5), 2412-3 (A) (2002).

We attributed the unexpectedly large improvement to "Lombard Effect", also known as "cafe effect". I believe cafe effect is the underlying cause of the "behavioral change" observed here.

Our interpretation was subsequently verified and extended by George Dodd and his student James Whitlock, who completed an MS thesis on the subject at Auckland University (2004).

I am certain that similar acoustical benefits can be brought to many other preschool classrooms. But also to group learning classrooms for older students as well. In fact, potential benefits ensue wherever simultaneous disscussions by many people take place in the same room.

I have not yet learned how to reliably estimate the substantial excess benefits obtained except by long-term measurements. Before and after measurements over ten school days would make a more credible report, but would usually be impractical to do without some kind of institutional support.

This finding has implication for revising reverberation time criteria for classrooms.

Probably the maximum reverberation time should be lower for group learning rooms than for lecture spaces. Perpaps the maximum unoccupied reverberation time should be reduced to 0.4 sec, rather than the 0.6 sec now required by ANSI S12.60-2002.

Thank you again for sharing this interesting and useful report.

David Lubman, FASA
Acoustical Consultant
Westminster, CA USA