Combination Tones in Sound and Light^*

Abstract

WHEN two notes are sounded together, the listener may hear in addition other notes which are not overtones of either of the originals. Theyare combination tones, the frequencies of which are linear algebraic functions of the primaries. Let us denote the latter by m and n. The most powerful combination tone has a frequency equal to the difference between m and n: a note of frequency m + n is much more difficult to observe. There may be notes of other frequencies, m + 2n, 2m + n … but these are weaker still. A full description of the effect is given by Jeans in “Science and Music”, p. 287 et seq. It is possible to make experimental arrangements by which the existence of combination tones may be plainly demonstrated. Some of these arrangements are described in the present note.