The Discrimination of Transducers against Reverberation

The directivity index characterizes the directional properties of an electro-acoustic transducer with respect to its ability to radiate sound power or discriminate against noise originating in the surrounding medium. Of greater interest in echo ranging is the transducer's ability to discriminate between the echo from the target at which it is pointed and the reverberation returned from all directions. This discrimination may be measured by quantities called reverberation indices, one of which concerns volume reverberation and the other surface and bottom reverberation. In this paper, the directivity and reverberation indices are defined and their inter-relations are studied, and approximate formulas are obtained that enable them to be calculated without performing tedious integrations.