THE 
LONDON, EDINBURGH ayn DUBLIN 
PHILOSOPHICAL MAGAZINE 
AND 
JOURNAL OF SCIENCE. 
[FOURTH SERIES.] 
FEBRUARY 1860. 
XII. On Vowel Sounds. By M. Hetmuorrz*, 
A MUSICAL note is produced by a periodical motion of the 
air repeated in the same manner at equal and sufficiently 
small intervals of time. The motion during each period of 
oscillation may be quite arbitrary, provided that the same motion 
which took place during the first period be repeated in like man- 
ner in all subsequent ones. 
If, in each period of oscillation, the small particles of air move 
to and fro exactly in the same manner as the centre of gravity 
of a pendulum when its amplitude is very small, we hear only a 
simple and single note, whose pitch is determined by the number 
of equal periods contained in a second. In this case the velocity 
as well as the pressure of the air at any point of the mass of air 
in motion, may be represented mathematically by a simple ex- 
pression of the form A sin (27nt+c). In a former memoir on 
resultant notes (Combinations- Tone), I have pointed out a method 
by means of which simple pendulum-like oscillations of molecules 
of air (or, as I proposed to call them, simple aérial waves) may be 
produced. To do so I made use of tuning-forks, which, when 
struck, do not communicate perceptible oscillations to the mass 
of air in which they are held. But when they are held at the 
mouth of a resonant tube whose deepest note is in unison with 
that of the tuning-fork, this deepest note of the fork is commu- 
nicated forcibly tothe air. Even when the tuning-fork can give 
still higher notes, it may be easily so arranged that these, its 
higher notes, shall not be in unison with the higher notes of 
* Translation, from Poggendorff’s Annalen, vol. eviii. p. 280, of a paper 
originally communicated by the Author to the Royal Bavarian Academy of 
Sciences. 
Phil. Mag. 8, 4, Vol. 19. No, 125, Feb, 1860. G 
