Laboratory 6 The frequency limit of a digital signal is proportional to the sampling rate, and is defined by the familiar equation: n = s/2, where n is Nyquist’s limit, and s is the sample rate. If frequencies above Nyquist’s limit are introduced into a digital signal, aliasing results. An aliased signal is reflected back below Nyquist’s limit to the extent that it would have exceeded it. Thus a sinewave 100z above Nyquist’s limit would be represented by an alias 100 hz BELOW the limit. Similarly, sounds with some partials above the limit and some below would suffer from a skewed set of partials. If the amplitude of the aliased partials is quite low, they might be masked by stronger, non-aliased partials, and the effect unnoticed. This experiment gives you a chance to simulate a low sampling rate in order to exaggerate the effect of the aliasing. The effective sampling rate for the patch in lab 6 is 5512.5 Hz. Download 06_Alias.pd. When you start the patch running you should hear a sawtooth wave at
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