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.
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.