The effect of a finite circular baffle on the axial response‐frequency characteristic of a central sound source in which sound from the back side of the diaphragm is completely suppressed was found to consist of an orderly series of peaks and valleys. The magnitudes and characteristic frequencies of these peaks and valleys depend upon the diameter of the baffle and the distance at which the response is measured. Experimentally determined values of the frequencies agree with values computed on the hypothesis that the phenomenon is one of interference between sound which reaches the measuring microphone directly from the source and sound which travels radially along the baffle and is “reflected” from its edge to the microphone. This assumption also accounts qualitatively for the increase of magnitude of the peaks and valleys with increasing distance from the baffle. As might be expected, baffles which are not symmetrical with respect to the sound source produce an irregular effect on the response.

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