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What Causes Amplifier Feedback?

Feedback can be created when a microphone picks up its own audio signal being projected from a speaker.
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  • Written By: Brooke Edwards
  • Edited By: Bronwyn Harris
  • Last Modified Date: 22 September 2014
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Few things are more disruptive to a soothing song or spirited speech than the painful shriek of feedback. Amplifier feedback occurs when the microphone picks up its own sound projected from the speaker and loops that sound back into the system, amplifying it again and again. This cycle happens so fast, with sounds looping back and forth at an estimated 1,000 times per second, that what comes out is feedback. Depending on the frequency that’s looping, the amplifier feedback can be a high-pitched screech or a deep, booming roar.

When amplifier feedback begins, the audience flinches and typically looks to the back of the room, hoping the person in the sound booth can help. The sound engineer can adjust volumes and frequencies, and should have taken key steps ahead of time to prevent feedback. However the person holding the microphone may also play a role in causing amplifier feedback.

If the person holding the microphone steps in front of the speakers, the loop is almost certain to begin. This is why amplifier feedback is even more likely with wireless microphones, which tend to be omnidirectional and allow the performer to walk in front of the speakers. The closer the microphone gets to the speaker, the louder the feedback is likely to be. Also, if the speaker or singer holds the microphone far from their mouth, the sound engineer has to turn up the volume to accommodate, increasing the likelihood of feedback occurring.

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While it's impossible to completely safeguard against amplifier feedback, there are many things that can be done to prevent it or stop it once it’s occurring. Tips include:

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Markerrag
Post 2

Feedback might not be desired for speeches, but guitarists love it. Well, some do at any rate. Throwing some controlled feedback in a song can work wonders.

Here's some trivia. What was the first time feedback was intentionally used in a song? 1964 when the Beatles opened "I Feel Fine" with Paul McCartney's bass feedback. The Beatles claimed at the time that it was an accident, but it was done on purpose and may have actually launched a revolution. Feedback wasn't desirable until the Beatles used it and showed how effective it could be.

Logicfest
Post 1

Believe it or not, some ear-piercing feedback can come in handy from time to time. Picture this. You've got a crowded hall full of people who are visiting. They are there to hear a featured speaker share some wisdom. The featured speaker goes up to the podium, tries to get the crowd's attention and is not successful. Initiating some feedback can grab their attention in a hurry and provide just the interruption needed to get a noisy crowd to pay attention.

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