The sound power output of a monopole source in a cylindrical pipe containing area discontinuities

Wenbo Duan , Ray Kirby

The sound power of a monopole source in free space is well known, and it is also known that the radiating sound power is not only determined by the source itself, but also the immediate environment surrounding the source. In this paper, a hybrid finite element method is used to study the sound power radiating from a monopole source placed close to a pipe discontinuity. It is found that while the sound power of a monopole source in free space increases as frequency squared, the sound power radiated from the same source in a cylindrical pipe is constant in the plane wave region. A sharp increase in sound power is then seen to occur when the first high-order mode cuts on; sound power is then seen to decrease as a function of frequency until the second high-order mode cuts on, and so on. It is also found that a wave reflected by a discontinuity placed close to one side of the source will interact with a wave on the other side travelling away from the source. This alters the sound power radiating from the source and has ramifications for the placement of monopole sources in piping systems.

Mots clés: Sound power; duct acoustics; finite element method

Domaines: Acoustique [physics.class-ph]

Wenbo Duan, Ray Kirby. The sound power output of a monopole source in a cylindrical pipe containing area discontinuities. Acoustics 2012, Apr 2012, Nantes, France. ⟨hal-00811097⟩