Fundamental frequency influences the relationship between sound pressure level and spectral balance in female classically trained singers

The influence of fundamental frequency (F0) on the relationship between sound pressure level (SPL) and spectral balance (SB) has been largely unexplored in the female singing voice. Five classically trained females performed a messa di voce across their musical F0 range. Average maximum SB rose with F0 by 0.27 dB/semitone (ST) to B4 and then decreased, while average minimum SB fell by 0.5 dB/ST to E5 and then generally rose. Of 318 tokens, 208 showed a linear SPL:SB relationship (R(2)>or=0.5), but F0 affected SPL:SB slope and intercept and their interaction above and below B4. The possibility that this reflects a change from subglottal inertance to compliance is discussed. Consistency of SB behavior change at B4 and E5 contrasted with variability in first-formant frequency. Nonlinear SPL:SB relationships did not arise from SB saturation. The presence of low-SPL "tails" may reflect the challenge in modifying vocal-fold adduction during crescendo and decrescendo. The results show that analysis of the SPL:SB relationship must take F0 into consideration.