Computer simulation of vocal tract resonance tuning strategies with respect to fundamental frequency and voice source spectral slope in singing.

A well-known concept of singing voice pedagogy is "formant tuning," where the lowest two vocal tract resonances ( f R1 , f R2 ) are systematically tuned to harmonics of the laryngeal voice source to maximize the level of radiated sound. A comprehensive evaluation of this resonance tuning concept is still needed. Here, the effect of f R1 , f R2 variation was systematically evaluated in silico across the entire fundamental frequency range of classical singing for three voice source characteristics with spectral slopes of -6, -12, and -18 dB/octave. Respective vocal tract transfer functions were generated with a previously introduced low-dimensional computational model, and resultant radiated sound levels were expressed in dB(A). Two distinct strategies for optimized sound output emerged for low vs high voices. At low pitches, spectral slope was the predominant factor for sound level increase, and resonance tuning only had a marginal effect. In contrast, resonance tuning strategies became more prevalent and voice source strength played an increasingly marginal role as fundamental frequency increased to the upper limits of the soprano range. This suggests that different voice classes (e.g., low male vs high female) likely have fundamentally different strategies for optimizing sound output, which has fundamental implications for pedagogical practice.