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Figure 4


Fig. 4. Echo features of a hollow hemisphere (r=25 mm) for 90 directions (-90° to 90°, in 2° increments) measured at a distance of 20 cm. (A) Relative amplitude. (B) Directional pattern of the impulse response function (white: positive amplitudes; black: negative amplitudes) Edges, 1st, 2nd reflections, see text and Fig. 5D. (C) Spectral directional pattern between 20 and 140 kHz.