The Room 2 class of Ilam School, asks :-

How can we reduce the amount of noise in our school hall?

Peter Gough, who works on acoustics at the University of Canterbury's department of electrical engineering, responded.

Unwanted noise in a large enclosed space such as a school hall comes from two main sources. External noise such as traffic noise is the easiest to reduce. Mostly this noise comes in through the windows and double glazing helps lower this to an acceptable level; however, even double glazing doesn't work if you leave the windows open!

The primary source of noise in a school hall comes from the sounds made by the occupants. The sound radiates out from the source (in a hall full of pupils-many sources) and reflects off the hard surfaces such as the walls, bouncing around until it finally dies away after about 1 sec or so. The length of time that an impulsive sound exists is called the 'reverberation time'. A good hall would have a reverberation time of less than 1 sec but any reduction in the reverberation time will generally lower the unwanted noise levels. You can do this by preventing the sound reflecting off the walls and ceiling. So hang the walls with heavy drapes and carpet the floor if that is possible.

But the most effective way to improve the acoustic feel of a noisy school hall is to hang a number of special sound absorbing panels from the ceiling. These 1.2m by 1.0m panels can be bought from any company that supplies thermal insulation such as fibre-glass batts and is frequently named 'sono-mat' or 'sound absorbing panels' or 'acousti-foam' to distinguish it from the more common thermal insulation.