Acoustic emission signals during leak from a circular hole and rectangular slits of different geometries were studied both analytically and experimentally. Rectangular slits had the same cross section area as the circular hole of 4mm diameter.
In the present experiment, a wide-band type transducer was used for receiving acoustic emission signals, and acoustic emission signals were transformed to digital signals through a digital osilloscope. Then $V_{rms}$ and frequency spectrum were obtained by processing digital signals.
Relationships between acoustic parameters and fluid mechanical parameters were derived analytically.
A quadrupole aerodynamic model was applied in the analysis of leak from the circular hole. In the case of constant pressure, $V_{rms}$ was proportional to root square of leak rate. In the case of constant hole diameter, $V_{rms}$ was also proportional to root square of leak rate from the circular hole.
A modified model based on dipole source mechanism and laminar effective diameter was applied in the analysis of leak from the reactangular slits. In the case of constant pressure, $V_{rms}$ increased as the laminar effective diameter of slit decreased. In the case of constant effective laminar diameter, the result was similar to that for leak from the circular hole.
The study of frequency spectra showed that frequency characteristics of leak signals from leak with same geometry but with different pressure were nearly identical.
