Influence of a Table on a Microphone's Frequency Response and Directivity
Teleconferencing applications often use a microphone placed directly on the table surface. A boundary or pressure zone microphone has its membrane mounted so close to a sound-reflecting plane that the membrane receives direct and reflected sounds in phase at all frequencies of interest, thereby avoiding destructive phase interference. However, in typical applications with small tables or a podium surface, a more detailed model is required to determine if the planar boundary assumption is still valid. Diffraction at the surface edges might significantly affect the frequency response. A comparison between the calculated and measured frequency responses indicate that the simulation gives 1/3 octave-band levels that are typically within 1 dB of measured values. As expects, the response from a small table is less uniform than for a large table.
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