Audio Technology / Recording / Mircophones / Proximity Effect ...

Usually, high-quality speech recordings require the sound source to be fairly close to the microphone's diaphragm. This may trigger a so-called proximity effect. Proximity effect is the increase in the low-frequency sensitivity of a microphone when the sound source is close to it. This is particularly true of cardioid, directional microphones. To counter that, most high-end directional microphones use a low-frequency roll-off filter to restore the response to its flat, natural balance. Some microphones have a user-selectable switch to control the filter. The proximity effect may be responsible for speech spectra showing emphasis in the low-frequency range, around the first and second harmonics.