subject: Sound In The Classroom And How It Affects Learning Ability [print this page] The size and shape of a classroom affects the sound levels and intelligibility of speech depending on the distance between teacher and pupils and can reduce learning ability.
At a distance of 1 metre, the sound level of normal speech is about 60 dB. However, each doubling of the distance reduces the sound level by 6 dB. For a pupil sitting 2 metres away from the sound source, the signal is 54 dB and at 4 metres, the signal is only 48 dB.
Typical background sound levels in a classroom are about 60 db, so a teacher needs to raise their voice level above this by about 15 dB. A suitable sound pressure level is about 75 dB to be heard distinctly, this level maybe difficult for many teachers to maintain all day. If a teacher remains at the front of the class, sound levels at the back could easily be lost in the background noise by the end of the day.
A microphone, amplifier and multiple speakers can boost the sound level and distribute it more uniformly in the classroom especially if ceiling speakers are used or speakers mounted on the side walls.
Very few speaker systems are designed especially for teachers in the classroom. Here are 6 tips for choosing a classroom active speaker system based on our experience and teacher feedback:
Basic design
Active speakers designed with a built-in amplifier reduce the amount of cabling and the costs of equipment as well as being quicker and easier to install
Steel grille
Steel grilles, rather than more common fabric grilles, stop pupils from damaging the speaker cones with fingers, pencils or missiles so extending the life of the system
Adequate sound level for a classroom (>75dB )
The sound level should be at least 15 dB above normal classroom noise of around 60 dB at 6 metres ie the back of the class, so less than 30 watts is unlikely to be loud enough and if much more than 30 watts the cost of the system is likely to be too expensive (so aim for 15 Watts RMS per channel)
Easy to control
It may seem obvious but many speakers have controls at the back (or front) that teachers can't reach without climbing up a chair ! A volume control and on/off switch at a sensible height is needed
Inputs for PC and DVD or other audio source
Shelf speakers and simple systems may only have one input - so you would have to re-connect every time you want to change the sound source. Two inputs are best for the classroom so that equipment is permanently connected.
Audible sound for voice
A wood speaker case and a flat frequency response is better than a sub-woofer amplifier system that accentuates the low frequency sounds, which is good for music but not so good for voice, especially for younger pupils who need to hear the teacher's voice clearly as their interpretation of speech is not as good as adults.
Classroom discussions may also benefit from additional microphones (or passing a microphone from pupil to pupil) so that everyone can hear and contribute.
An amplifier system needs to be designed especially for classroom use as the construction and size of a classroom is very different to the rooms in normal houses
Voice amplification is only a partial solution if the building design is poor for sound. The amplified sound may well interfere with teaching in adjacent classrooms if interior walls do not perform well as an acoustic barrier.
