An experimental examination of acoustic echo structure

The structure of the echoes from various solid bodies immersed in water is examined experimentally. The echo envelopes are compared with the theoretical forecasts of two earlier papers which respectively described and gave examples of the mechanism of echo formation applicable when short-wavelength, acoustic irradiation is incident upon a rigid body immersed in a fluid medium. The theory predicted that echoes are made up of discrete components associated with discontinuities in a certain function of the projection of the scattering body towards the transducers; it also forecast several types of behaviour of echo envelopes which depend on the degree of overlap of these echo components. The experimental results are in good qualitative agreement with the theory, while the small amount of quantitative evidence available tends, in the main, to give it support. In the cases where the experimental results do not agree with theoretical predictions, there are strong indications that this is due to departure from the postulate of an impenetrable scattering body.