Aliasing

To ensure that all frequencies entering into a digital system abide by the Nyquist Theorem, a low-pass filter is used to remove (or attenuate) frequencies above the Nyquist limit.

Figure 2: Low-pass filters in a digital audio system ensure that signals are bandlimited.

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Though low-pass filters are in place to prevent frequencies higher than half the sampling rate from being seen by the ADC, it is possible when processing a digital signal to create a signal containing these components.
What happens to the frequency components that exceed the Nyquist limit?

**Figure 2:** Low-pass filters in a digital audio system ensure that signals are bandlimited.
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