ABSTRACT
Sounds are an integral part of life, and absolute silence, a very unusual phenomenon, can exist only in anechoic chambers. Sounds are a source of information, for example, the communication we give or receive over the telephone, and a source of pleasure, as with music or birdsong. But sounds can also be unwanted, annoying or even damaging. When they fall into one of these latter categories, they are called noise. The level of disturbance from unwanted sound depends on the sound, the current situation, as well as one's personal response. A dripping tap, loud music or a typewriter may disturb
one person but not another. Annoying sound types are those that interfere with other activities, for example, when noise from a machine interferes with speech intelligibility. Damaging sound, on the other hand, can be evaluated more objectively because it results in hearing loss or other physiological problems.
