1 - Introduction to sound and noise

Abstract

This chapter introduces sound and noise. The discordant sound resulting from nonperiodic vibrations in air and unwanted sound are the two definitions of noise. Noise draws emotional responses on conscious and subconscious levels. It annoys, awakens, angers, distracts, frustrates, and creates stresses that result in physiological and psychological problems. The effects of noise may be categorized as follows: noise-induced hearing loss, nonauditory health effects, individual behavior effects, noise effects on sleep, communication interference, and effects on domestic animals and wildlife. It is well established that hearing damage can result from exposure to the noise of sufficient intensity and duration. Hearing loss may be temporary or permanent. Noise can alter the normal functions of the endocrine, cardiovascular, and neurological systems. Human performance is affected by noise, especially those tasks requiring information gathering or analyzing processes. Noise simply may be distracting or be so disturbing that it is impossible to think. Noise extends well beyond the workplace. Sound is the result of a source setting a medium into vibration. As a sensory organ, the ear is second only to the eye with regard to its importance as a means of contact with man's surrounding environment. The chapter also discusses the physics of sound. Sound may be described in terms of three variables: amplitude (perceived as loudness), frequency (perceived as pitch), and duration (time). Frequency can be defined as the number of compressions and rarefactions per unit time (sec) qualified to a given medium, usually air.