The engineering terminology for one use of Fourier transforms. By breaking up a wave pulse into its frequency spectrum
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(1)
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the entire signal can be written as a sum of contributions from each frequency,
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(2)
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If the signal is modified in some way, it will become
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(3)
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(4)
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(5)
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(6)
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where 
is known as the "transfer function." Fourier
transforming 
and 
,
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(7)
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(8)
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From the convolution theorem,
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(9)
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