Proximity effect

Proximity effect is a boost in bass response that happens as a sound source gets closer to a directional microphone, meaning any mic with a cardioid, figure-8 or similar pattern rather than omnidirectional. The closer the mouth gets to the capsule, the deeper and warmer the voice tends to sound.

This effect is why many podcast and broadcast voices sound rich and full, since hosts are often coached to work a mic at a close distance specifically to take advantage of it. Used well, it adds warmth. Used inconsistently, it makes a voice sound boomy in some sentences and thin in others as the speaker shifts position.

Keeping a stable, consistent distance from the mic, roughly a fist's width for most cardioid dynamics, avoids the uneven bass buildup that comes from leaning in and pulling back during a conversation. A pop filter mounted at a fixed distance can also help a host maintain that consistent gap without thinking about it during an animated conversation, since it acts as a physical reminder of where to sit.