Abstract: The outputs of sound sources are being reported in a variety of ways, so that it is difficult to grasp quickly their relative significance. For some kinds of noise, computed sound-power levels are frequently given, whereas only sound-pressure levels are ordinarily measured. The whole picture can be clarified by routine use of source level. The (spherical) source level is the sound-pressure level at a reference distance of 1 m (unless otherwise specified) from an equivalent point source. Source level is equal to sound-power level plus an adjustment for the medium and units of measurement. In a free spherical sound field, sound pressure p varies inversely as distance r; thus, source level is 20 log (p×r/p0×r0), where the subscript 0 identifies reference quantities. Hemispherical source level is the sound-pressure level at reference distance from an equivalent hemispherical source. Axial source level is the sound-pressure level produced at reference distance on the axis of maximum response. Duct source level is the sound-pressure level of a free plane wave in a duct of reference cross section that would transmit sound power equal to that emitted by the actual source into the duct.
Publication Year: 1963
Publication Date: 1963-05-01
Language: en
Type: article
Indexed In: ['crossref']
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