Susceptibility to noise in general and to particular noises varies greatly among individuals. It is a difficult question to discuss. It is well known that noises hinder sleep. Physicians say that certain persons, especially those suffering from nervous diseases, are seriously injured by noise and vibration. Everyone knows that in many ways noises interfere with the comfort and tranquillity of life. Quiet is especially important at night in residential districts and near hospitals and schools.

Noises are greatly increased by the reflection of sound waves from the hard surfaces of pavements and building walls. Limitation of the height of buildings is, therefore, a means of noise reduction. Vegetation, on the other hand, tends to dampen sound waves - another reason for providing conditions favorable for trees and grass in residential districts.

Many kinds of noises are preventable, but others appear to be inseparable from traffic, business, and manufacturing processes. In these cases segregation appears to be the best solution.