What Is Microphone Feedback?
Have you ever accidentally placed your microphone too close to your speaker and heard a loud, high-pitched sound? That sound is called feedback. By definition, feedback is a positive gain loop between an input and output source, such as a microphone and a speaker.
When a microphone is sending a signal to a speaker in the same room, there’s a risk that a feedback loop will be created. The microphone signal is amplified through the speaker, then the sound from the speaker is picked up by the microphone and amplified through the speaker again, causing the system to overload and feedback.
The result is a howling sound that is loud that in the worst cases can damage your equipment and more importantly, your hearing
To avoid feedback, set the mic preamp and loudspeaker levels to the lowest setting. Increase the preamp gain until a sufficient level is present, then gradually increase the loudspeaker level until you can hear the microphone clearly. If feedback occurs, try the suggestions listed below.
Importance of the Polar Pattern
The choice of the polar pattern of a microphone will have a huge impact on triggering or preventing the feedback. Make sure to select the pattern that will be the most sensitive to the sound, and the least sensitive to the sides and rear.
Cupping or covering the grille of a directional microphone can alter the polar pattern of the mic, making it omnidirectional and more prone to feedback.
How to prevent microphone feedback
- Before connecting a microphone, it is imperative that you reduce the input gain as low as possible, including enabling the pad switch if available. Then at a low volume, slowly bring the gain up on the input channel until you just start to see level and hear sound.
- Find the maximum gain-before-feedback and set it slightly less than that.
- In live environments, choose a dynamic microphone rather than a condenser.
- Do not position the microphone in front of a loudspeaker.
- Position microphones close to their sound sources.
- Point directional microphones away from monitors.
- Turn down the microphone gain and volume.
- Do not cup the microphone.
- Use in-ear monitors rather than loudspeaker monitors.
- Reduce the number of open microphones.
- For live environments, use an equalizer to find and eliminate the frequency that generates the feedback.