Vocal Loudness Variation With Spectral Slope

Abstract

Objective This investigation addresses the loudness variations in sones achievable with spectral slope variations (higher harmonic energy) in human vocalization and compares it to the sound pressure level (SPL) variations typically reported in the voice range profile (VRP). Method The primary methodology was computational. The ISO standard 226 was used to convert SPL values to sones for a 125- to 1000-Hz range of fundamental frequency and a –3 dB/octave to –12 dB/octave range of spectral slope. In addition, a retrospective analysis of human subjects' VRPs was conducted, and the experimental results were compared to the theoretical results. Results A very small range of SPL variation (less than 5 dB) in the VRP can produce a large range of loudness. The sensitivity can be on the order of 4 sones per dB SPL change. Conclusion For vocalization in the modal register, loudness variation is not well described by SPL change in dB, especially at high fundamental frequencies where the SPL range in the VRP becomes very small but sizeable loudness variations are still possible.

The Effect of Single Harmonic Tuning on Vocal Loudness

“…Computation of loudness in sones from a sound spectrum followed a previous publication. 4 A script published by Tackett was used to convert SPL to loudness level in phons and then to loudness in sones in the range of 10−90 phons. 12 Equations are given in the earlier publication and are reproduced here in the Appendix.…”

“…12 Equations are given in the earlier publication and are reproduced here in the Appendix. 4 The procedure is based on International Standards Organization ISO 226:2003, reviewed and confirmed in 2014. Frequencies available for direct calculation were 20 Hz−12.5 kHz in third-octave steps.…”

“…These changes in loudness were compared to changes in loudness achievable with overall spectral slope change in the previous publication. 4…”

“…In a recent paper by Titze and Palaparthi, it was shown that spectral slope change is highly effective for loudness regulation. 4 For modal (chest) register, a small change in sound pressure level (SPL) from a variation in spectral slope was shown to produce a large change in loudness. The investigation was a new step toward understanding control of loudness in vocalization, but did not yet consider how harmonic tuning by vocal tract resonances can affect perceived loudness.…”

“…The fundamental question to be answered in this study is to what extent perceived loudness can be altered by tuning a vocal tract resonance to a single harmonic and how that compares with multiple harmonics being reinforced with spectral slope variations described earlier. 4 Both techniques are used in singing.…”