What is Comb Filtering?

Comb filtering is an audio effect that occurs when a sound signal is combined with a slightly delayed version of itself. The interaction between the two signals causes certain frequencies to reinforce each other while others cancel out.

This pattern of alternating boosts and cuts in the frequency spectrum resembles the shape of a comb, which is where the term comes from. The result can make the audio sound hollow, thin, or colored.

Comb filtering often occurs when multiple microphones capture the same sound source at different distances, or when sound reflections from walls and surfaces reach the microphone slightly later than the direct sound. Engineers minimize comb filtering by adjusting microphone placement, controlling room reflections, or aligning signals in a digital audio workstation.