The Proximity Effect in Microphones
The Proximity Effect might sound like the title of a Tom Cruise spy film, but it is a critical concept to understanding the sound one gets from certain microphones. This effect is present in all microphones, except for omnidirectional types. The closer the microphone gets to the sound source, a human mouth while singing for example, there is an increase in low-frequency response. If you are aware how much deeper your voice sounds as you move the microphone closer to your mouth, you’re experiencing the proximity effect.
Microphones use capsules with very thin diaphragms that react to different sound pressure levels and convert that acoustic energy into an electrical signal. Proximity effect is the cause of varying pressure differences between the front and rear of a microphone’s diaphragm.
Directional microphones pick up sound from both the front and the back of the mic’s diaphragm and thus experience the effect. The reason omnidirectional microphones do not is they only pick up sound using the front of the diaphragm, while the rear is fixed and does not move.
The effect is most noticeable in sources with a lot of low frequency content, such as male voices. Radio personalities have long used the proximity effect to make their voices sound deeper and more powerful.
Although you can use this to help enhance the sound of the source, you must be careful not to add too much low frequency information. One of the reasons that singers use pop screens in front of mics when recording is because the accentuated low frequencies from the effect mean that the mic will pick up more plosives (popped consonant sounds like D, G and B).
The proximity effect can also be problematic when a directional microphone is positioned close to the sound hole of an acoustic guitar and pointed directly at it. That is where most of the bottom end of the guitar emanates from, and the effect exaggerates it more. If that sound hole tone is desired, it would be better to use an omnidirectional microphone because it doesn’t exhibit the effect.
Please contact us at 610-626-7600 for any of your microphone rental or purchase needs or to ask questions on which microphone would be best for a particular event or location.