The acoustics of registers and resonances in singing

The wide range of the singing voice, from below C2 (65 Hz) to above F6 (1397 Hz), requires a number of strategies that can involve different mechanisms of laryngeal vibration and various adjustments of the vocal tract resonances. The adjustments are made because a vocal tract resonance can boost the radiation of a voice harmonic when it falls close to a resonance frequency. Here we report how singers with different voice categories tune their vocal tract resonances. For the lower voices, the lowest resonance R1 is sometimes tuned to a high harmonic, while high voices consistently tune R1 to the fundamental over a range of about C5 to C6 (523 to 1046 Hz). The second resonance, R2, can be simultaneously tuned to the second harmonic in the pitch range C5 to F5 (523 to 700 Hz). At the very highest pitches, sopranos can no longer increase R1 sufficiently and must then switch to adjusting R2 so its frequency is close to that of the fundamental.