Proximity effect (audio)

The proximity effect in audio is an increase in bass or low frequency response when a sound source is close to a directional or cardioid microphone. Proximity effect is a change in the frequency response of a directional pattern microphone that results in an emphasis on lower frequencies. It is caused by the use of ports to create directional polar pickup patterns, so omni-directional microphones do not exhibit the effect (this is not necessarily true of the "omni" pattern on multipattern condenser mics, which create the "omni" pattern by summing two back-to-back cardioid capsules, which may or may not share a common backplate.) Proximity effect can be viewed in two ways. In some settings, sound engineers may view it as undesirable, and so the type of microphone or microphone practice may be chosen in order to reduce the proximity effect. On the other hand, some microphone users seek to intentionally use the proximity effect, such as beat boxing singers in hip hop music. Depending on the microphone design, proximity effect may result in a boost of up to 16 dB or more at lower frequencies, depending on the size of the microphone's diaphragm and the distance of the source. A ready (and common) example of proximity effect can be observed with cardioid dynamic vocal microphones (though it is not limited to this class of microphone) when the vocalist is very close to or even touching the mic with their lips. The effect is heard as a 'fattening up' of the voice. Many radio broadcast microphones are large diameter cardioid pickup pattern microphones, and radio announcers are often observed to employ proximity effect, adding a sense of gravitas and depth to the voice. Proximity effect is sometimes referred to as "bass tip-up." To explain how the proximity effect arises in directional microphones, it is first necessary to briefly describe how a directional microphone works. A microphone is constructed with a diaphragm whose mechanical movement is converted to electrical signals (via a magnetic coil, for example).