ABSTRACT
This chapter emphasizes reduction of noise at its source, which should always be the primary goal of the acoustical engineer. However, in addition to source control, significant noise reduction can be obtained by controlling the reflected noise which accumulates in enclosed interior environments. This phenomenon, commonly called reverberation buildup, is best observed in indoor swimming pools where the sound from the diving board or a shout continues on for seconds, or with a crowd present, there is often an overall din which makes conversation difficult. Basically, reverberation buildup occurs when there is a lack of absorbing surfaces, and the noise levels increase until the rates of sound generation and absorption are equal. The walls, floor, and ceiling in industrial plants are typically acoustically hard, and as such, significant reverberation buildup is common. The chapter discusses the basic physics of reverberation and those measures available for its control. Thus, the control of reverberation can be an effective noise reduction measure.
