When two pure tones, with frequencies of 440 Hz and 448 Hz, are sounded together, a single pure tone is heard, with a frequency of 444 Hz (the average of the two pure tone frequencies). The amplitude of the resulting sound varies with time, exhibiting a discernable "beating". The beat frequency is 8 Hz, equal to the difference between the two frequencies.
If two different pure tones, with frequencies of 440 Hz and 432 Hz, are sounded together, a single pure tone having a frequency of 436 Hz is heard. The amplitude of the resulting sound again varies with time, with a beat frequency equal to 8 Hz.
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Last updated: 18 Nov 1999
Comments: bland@indiana.edu