University of Edinburgh

Classroom Acoustics

Part two

What happens if you can't actually hear what the teacher's saying? That's the problem. Not every child has an equal opportunity in the classroom.

The physics behind it.
You all know the inverse square law. So as you double the distance from somebody talking, you reduce the volume of your voice by half. So in the average classroom you get half way to the back; the average person will speak about 70 decibels; by the time you reach the back of the class it's down at 50db. The problem is, the average background noise in the classroom; the ambient noise, is 60db. Where is the teacher's voice? What happens to that?

So by the time that you reach the middle of the classroom pretty much the teacher's voice is at the same volume [as the ambient noise]. Don't the NDCS recommend 15db signal to noise ratio for early years 4-8 year-old children? You don't even get that; you're only going to have a maximum of 10 if you're sitting in a good location in the class.

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