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Speaker 1: Welcome to brain Stuff from how stuff Works dot com

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Speaker 1: where smart happens. Join Josh and Chuck, the guys who

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Speaker 1: bring you stuff you should know, as they take a

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Speaker 1: Stuff Guide to the Economy from how Stuff Works dot Com,

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Speaker 1: available now exclusively on iTunes. Hi. I'm Marshall Brain with

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Speaker 1: today's question, what causes that howling sound in p A systems?

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Speaker 1: A simple p A or public address system consists of

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Speaker 1: a microphone and amplifier and one or more speakers. Whenever

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Speaker 1: you have those three components, you have the potential for feedback.

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Speaker 1: Feedback occurs when the sound from the speakers makes it

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Speaker 1: back into the microphone and is re amplified and sent

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Speaker 1: through the speakers. Again. Imagine that you place the microphone

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Speaker 1: in front of a speaker. Now you tap on the microphone.

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Speaker 1: The sound of that tap is through the amplifier, comes

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Speaker 1: out the speaker, and it re enters the microphone. That

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Speaker 1: cycle repeats over and over. This loop happens so quickly

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Speaker 1: that it creates its own frequency, which we hear as

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Speaker 1: a howling sound. The distance between the mic and the

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Speaker 1: speaker has a lot to do with the frequency of

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Speaker 1: the howling, because that distance controls how quickly the sound

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Speaker 1: can loop through the system. If you're setting up a

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Speaker 1: sound system and you want to avoid feedback, there are

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Speaker 1: a few general rules that can help you avoid the problem. First,

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Speaker 1: make sure the speakers are in front of the microphone

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Speaker 1: and pointing away from the microphone. If the speakers are

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Speaker 1: behind the microphone, then feedback is nearly guaranteed. Second, use

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Speaker 1: a unidirectional microphone. Third, place the microphone close to the

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Speaker 1: person who's speaking or performing, And fourth, if you have

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Speaker 1: access to an equalizer, dampen the frequencies where feedback is occurring.

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