Concepts of perceived noisiness, their implementation and application.

Abstract

The concepts and methods of estimating the perceived noisiness of sounds from subjective and physical measurements are described. A general method, called Effective Perceived Noise Level (EPNL), of estimating the perceived noisiness of a single sound or a total sound environment taken over a 24-hour period is proposed, and its relations to the Effective Composite Noise Rating (ECNR) scheme are discussed. It would appear that the average threshold of general noisiness or annoyance for the sound environment of a typical residential area occurs at about 50 PNdBt for sounds measured indoors and at 70 PNdBt for sounds measured outdoors; these threshold values can be utilized to advantage in conjunction with EPNL and ECNR. The virtue of using EPNL and ECNR, which in essence, are the same in certain applications as “CNR,” “NNI,” and “Q̄” quantities developed in the U. S. A., Great Britain, and Germany, respectively, is that they can combine the variable factors of duration, number of occurrences, spectrum and intensity of sounds into a single unit that allows meaningful intercomparisons of the over-all effect upon human behavior of noises and noise environments that may differ markedly from each other in these dimensions. Tolerable limits are proposed in terms of EPNL, ECNR, CNR, NNI, and Q̄ for: a) annoyance due to noise generated and measured outdoors but heard outdoors and/or indoors; b) annoyance due to noise present indoors; and c) damage risk to the ear for noise present at the listener's ears.