Page "Phonation" Paragraph 2

The sound that the larynx produces is a harmonic series.

In other words, it consists of a fundamental tone ( called the fundamental frequency, the main acoustic cue for the percept pitch ) accompanied by harmonic overtones, which are multiples of the fundamental frequency.

According to the Source-Filter Theory, the resulting sound excites the resonance chamber that is the vocal tract to produce the individual speech sounds.