The sound spectra of three vowels, spoken, analyzed, and
recorded by J. Hughes using the program fftscope by H. S. Lu. The
vertical dashed lines indicate the corresponding formant frequencies
of an ``average'' male voice from Table 15.3 (p. 346) of the
textbook The Science of Sound, 3rd Edition, by T. D. Rossing,
F. R. Moore, & P. A. Wheeler (RMW).