ENGINEERING AWAY NOISE.

The methods of electrical engineering are being used to understand and solve noise problems. Safety standards and the effects of noise on man are discussed. Parallels between electrical engineering and the science of acoustics are presented. Noise evades definition in terms of the physical nature of sound. Whether a sound is noise or not depends on the listener, the distinguishing characteristic being the undesirability of the sound. Hence, noise can be best defined as, simply, ″any unwanted sound.″ Through statistical analysis of the results of tests on large numbers of people, annoyance curves have been constructed. Where control of annoyance is of primary importance, as in zoning laws, maximum intensities are often specified for each of several frequency bands. Hearing loss is related not only to the intensity of the noise exposure, but also to the time duration of the exposure. Higher sound levels can be tolerated for shorter periods of time than can lower sound levels. The federal Walsh-Healey act of 1969, which was designed to protect the worker from hazardous noise, defines a set of standards for permissible noise exposure.