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Collaboration, Voice & AV · Foundational

Feedback

A howl or squeal caused when loudspeaker sound re-enters a microphone and is amplified repeatedly in a loop.

Definition

Acoustic feedback occurs when loop gain at some frequency reaches unity. Reducing it involves placing microphones closer to talkers and farther from loudspeakers, using directional microphones with loudspeakers in their nulls, limiting open microphones and applying notch filters. Calculations of potential and needed acoustic gain predict whether a system can achieve the required level.

Example

Moving the presenter's microphone behind the main loudspeakers eliminates ringing at 1 kHz.

Exam tip

Microphone placement is the most effective feedback fix; EQ is a last refinement.

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