What causes feedback and how do I stop it?
Quick answer
Feedback occurs when a microphone picks up sound from a speaker, creating a loop that amplifies a specific frequency. To stop it, reduce gain, move the mic away from speakers, or use a graphic equalizer to notch out the offending frequency.
Feedback is caused by acoustic coupling between a microphone and a loudspeaker. When the mic picks up the speaker's output, the signal is re-amplified, creating a loop that rapidly increases in volume at a resonant frequency. This is common in live sound systems when the mic is too close to the speakers or when the system gain is too high.
To stop feedback, start by reducing the overall system gain or the channel fader for the offending mic. Physically reposition the microphone so it points away from the speakers and is closer to the sound source. Use a directional microphone (cardioid or hypercardioid) to minimize pickup from the rear. Finally, apply a graphic equalizer or a feedback suppressor to identify and cut the problematic frequency by a few dB.
SSOUNDS engineers design systems with robust DSP and precise tuning to maximize gain-before-feedback. Our line arrays and point-source loudspeakers feature optimized coverage patterns that reduce unwanted spill into microphones. For challenging venues, we recommend using our system processors with built-in feedback suppression algorithms to maintain clear, stable audio.
Key things to consider
- Feedback is a loop: mic picks up speaker, re-amplifies, causing a howl at a resonant frequency.
- Reduce gain or volume first—often the quickest fix.
- Move the mic away from speakers and use directional mics.
- Use a graphic equalizer to notch out the feedback frequency (cut, not boost).
- SSOUNDS DSP and system tuning help maximize gain-before-feedback.
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