Comb filtering is a common phenomenon in audio that occurs when a sound wave is combined with a delayed version of itself. This results in a series of peaks and notches in the frequency response of the combined signal, resembling the teeth of a comb. These peaks and notches occur at regular intervals and can cause certain frequencies to be amplified while others are attenuated, resulting in a distorted and uneven sound.
The most common cause of comb filtering in audio is the reflection of sound waves from nearby surfaces, such as walls, floors, ceilings, and furniture. When sound waves are reflected, they travel a longer distance before reaching the listener's ears, creating a delay. This delayed sound wave then interferes with the original sound wave, resulting in comb filtering.
Comb filtering can be minimized by reducing the amount of reflected sound in a room through acoustic treatment or by adjusting the placement of speakers to minimize reflections.