Contains the full lesson along with a supporting toolkit, including teachers’ notes.
Cities are full of sound – from people, factories, music, alarms, cars, trams, trains, planes, construction, animals (though not as much as fifty years ago).
What is sound? When does sound become noise? Is there a quantifiable distinction between them or is ‘noise’ a purely subjective label? Does noise have an adverse effect on people? In this lesson we will try to clarify these and other questions.
What is sound?
Our ears are able to detect rapid variations in air pressure as long as they are in the frequency range of about 16 Hz (hertz) to 16 kHz and their intensity is greater than one thousand millionth of atmospheric pressure. Because they are so sensitive our ears can be permanently damaged by very loud sounds.
What is noise?
The simple answer is that noise is unwanted sound. What characterisesnoise is more difficult to say but the following factors are significant: loudness and frequency range, whether it is continuous or intermittent, the time of day and whether it matches our mood or needs at the time. So what might otherwise qualify as pleasant music may become ‘noise’ if it interferes with our ability to work, communicate or relax.
In the centre of a city where there are generally more people and vehicles, noise levels are high. In built-up areas sound bounces off hard surfaces while along suburban and country roads the vegetation and soft ground absorb much of the sound.