Equipment for measurement of free-field characteristic of e.g. directional microphone

摘要

The equipment includes an acoustic waveguide (10) filled with absorbent wadding (11) to a length (e) of about 30 cm. The microphone under test (2) and a reference microphone (3) with a calibration amplifier (4) are placed at its mouth at a distance (l) of e.g. 50 cm from a loudspeaker (1). The voltages produced by both microphones are measured by multimeters (6,7). For tests at 100 Hz to 4 kHz, a tubular waveguide with a diameter of about 4 cm and length of about 80 cm is chosen.