Proximity Effect
Definition
A bass boost that occurs naturally when a directional microphone (cardioid, figure-8) is placed very close to a sound source — typically within 15 cm. The closer the source, the more pronounced the low-frequency emphasis. Omnidirectional microphones do not exhibit proximity effect.
In Simple Terms
The closer you get to a directional microphone, the more bass it picks up. Singers who eat the mic get a boomy, warm sound; step back and it thins out. Radio DJs and podcasters use this on purpose for that deep, intimate voice sound.
In Practice
A vocalist recording at 5 cm from a cardioid condenser exhibits significant low-frequency buildup below 200 Hz. Moving to 20 cm reduces this proximity-induced bass boost while maintaining the natural tone of the voice. The engineer uses a high-pass filter to compensate when close placement is preferred.