RMW refers to the textbook The Science of Sound, 3rd
Edition, by T.D. Rossing, F.R. Moore, & P.A. Wheeler
RMW, page 353, exercises 2, 6, 8.
RMW, page 396, exercise 2.
Suppose you sing with your vocal tract filled with helium, in
which the speed of sound is approximately 930 m/s. Does this change
the frequency of vocal cord vibration? Does it change the formant
frequencies? By how much?
The address of this page is
http://www.physics.rutgers.edu/~jackph/2005s/hw10.html