Listen to Maria Callas, Luciano Pavarotti and others to see examples of
different human voice bandwidths.

 Maria Callas and Luciano Pavarotti singing the
same song: Ave Maria of Schubert. They both have a very wide bandwidth voice,
with a larger number of harmonics, compared to a normal man and woman. The voice
bandwidth of Callas is in the interval of relatively higher frequencies compared
to that of Pavarotti. Both voices are bandlimited.
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Barbra Streisand and Céline Dion have voices with
very wide frequency bandwidth, which includes the similar harmonic frequencies.
However, their voices have a different mixture of the harmonic frequencies. In
other words, the analytical form of  Fourier transforms of their voices are
different.
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