Line Sources

Sometimes noise sources are distributed more like idealized line sources. Examples include the sound radiated from a long pipe containing fluid flow or the sound radiated by a stream of vehicles on a highway.

If sound sources are distributed continuously along a straight line and the sources are radiating sound independently, so that the sound power/unit length is W′ watts/metre, then assuming cylindrical spreading (and we are located in the far acoustic field again and ρc = 400 rayls):

(3.61)

so,

then

(3.62)

and for half‐space radiation (such as a line source on a hard surface, such as a road)

(3.63)