In addition to sound that comes directly from the source, a microphone captures sound that is reflected by surrounded surfaces as well. Direct sound and reflected sound are interferring. As the reflected sound had a longer travel, it is not in phase with the direct sound. This leads to cancellations of several frequencies/frequencie ranges and therefore a noticeable coloration of the sound: the comb filter effect. To reduce this effect it is advisable to either keep the travel of the reflected sound as close to the travel of the direct sound or let it attenuate as much as possible. Attenuation can be achieved by a very long travel, by absorbing, by choosing a microphone pattern that attenuates sound that arrives at the angle of the reflected sound.
Height of sound source | m |
Height of microphone | m |
Vertical angle of microphone | ° |
Microphone pattern | |
Ground distance betw. sound source and mic. | m |
Absorption of the ground | |
fully effective at/above frequency | Hz |
absorbing factor (1=fully absorbing) |
Brown noise:
White noise:
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