Testing a hydroacoustic radiator in a reverberant tank based on recording the sound field in the air above the tank

Abstract

A method for calibrating a monopole sound source in a water tank with reflective side walls and bottom is considered. The idea of the method is based on the phenomenon of anomalous transparency of the water-air boundary for a sound source located at a shallow depth. This boundary plays the role of a filter that prevents waves reflected from the side walls and bottom from entering the air. For a shallow source, the field in the air will be approximately the same as for a source located at the same depth in a homogeneous water half-space. This field is described by a well-known analytical formula that makes it possible to estimate the source strength in water based on the sound intensity level measured in air.

Figures (10)

• Figure 1: Pressure magnitude on the water surface at frequencies of 5 kHz (solid line) and 20 kHz (dashed line). The point source exciting the sound field is located at depths of -3 cm (a) and -7 cm (b).
• Figure 2: Pressure magnitude in a cylindrical water tank with a solid side boundary and bottom (-1 m $<$$z$$<$ 0 m) and the real part of the complex pressure amplitude in the air above the tank (0 m $<$$z$$<$ 0.3 m). The sound source is a sphere with a radius of 2 cm (a) and 5 cm (b), pulsating at a frequency of 5150 Hz. The center of the sphere is at a depth of -3 cm (a) and -6 cm (b).
• Figure 3: Air pressure at $r = 0$ generated by a source in a water half-space (solid thick line) and in a tank with rigid (thin solid line) and soft (dashed line) side boundaries and bottom.The calculations are performed for sources whose radii, $a$, and center depths, $z_0$, are indicated on the graphs.
• Figure 4: (a) The same as in Fig. 2(a) but for frequency $f$ = 5110 Hz. (b) The same as in Fig. 3(a) but for frequency $f$ = 5110 Hz.
• Figure 5: Calibrated sources (left) and schematic drawings of their constructions (right).