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aliasing

When a sample-rate change makes two different frequencies produce the exact same sequence of numbers, so one is mistaken for (impersonates) the other.

A signal's frequency, viewed at a given sampling rate, is said to alias when it is indistinguishable from a different frequency -- both produce the identical sequence of samples, so one frequency is said to "alias" as the other. It is the central obstacle any sampling or rate-changing operation has to manage.

See also

discrete-time signal
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