Recent discussions as to the nature of vowel-sounds have led us to make experiments (partly with an apparatus constructed some years ago for the same purpose) upon the effect of a periodic variation of intensity of a simple tone.

It is obviously impossible to secure a simple harmonic variation, so we endeavoured to produce a displacement varying as

1 − cos mt.

An organ-pipe, giving a tone very free from harmonics, was sounded on one side of a partition in which were cut a series of large holes.