It is the purpose of this paper to cover briefly the basic characteristics of sound as they dictate the design of instruments. The discussion of the equipment will be confined to available commercial instruments, and stress will be given to those instruments which are particularly useful for field evaluation of noise problems as they relate to industrial hygiene.
NATURE OF SOUND
Sound has been defined by the American Standards Association1 as "an alternation in pressure, stress, particle displacement, particle velocity, etc., which is propagated in an elastic material, or the superposition of such propagated alternations." In the case of industrial noise, the elastic medium is air and the alternations in pressure are variations above and below atmospheric pressure. Atmospheric pressure under standard conditions is 1.01325 × 106 dynes per square centimeter. The pressure variations with which we are concerned in sound have an approximate range of 0.0002
WILLIAMS CR. Instruments for Measuring Sound. AMA Arch Otolaryngol. 1955;62(4):414–425. doi:10.1001/archotol.1955.03830040068012
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