Computer Music: Musc 216
Aliasing is the term used to describe the unwanted frequencies which are produced when a sound is sampled at a rate which is less than twice the frequency of the highest frequency component in the sound. These unwanted frequencies are typically high frequency tweets and whistles.
[From EMU Ensoniq's Glossary
of Electronic Music Terms]
Fig. 1 Sound with a frequency of 1500 Hz sampled at