Acoustic emission spectra due to leaks from circular holes and rectangular slits

Acoustic waves emitted during a leak are studied both theoretically and experimentally. Two geometries of the leak are considered: a circular hole and a rectangular slit. An expression for the dependence of the frequency of the emitted signal on the pressure difference of the fluid across the leak and the dimensions of the hole or slit is derived. The expression is found to agree with the experimental results obtained for the case of a circular hole over a wide range of pressure differences and hole diameters. It is concluded that a leak may be treated as a resonator that emits acoustic waves at a sharp resonant frequency, besides its well-known characteristics of producing low-frequency noise due to the increase of turbulence in the fluid around the area of the leak.