Reconsidering the formant correction formula in VoiceSauce

VoiceSauce (Shue et al., 2011) is an acoustic signal analysis software widely used for analyzing voice quality for various purposes (e.g., linguistic phonation acoustics: Keating et al., 2023; articulatory correlates: Wu & Zhang, 2023; speech disorder: Asiaee et al., 2022; singing: Meireles, 2016). One of the voice quality measurements provided by VoiceSauce is the amplitude difference between the first and second harmonics (H1–H2), a measurement widely used as a proxy for the degree of constriction of the vocal folds. The built-in formant correction formula (Iseli et al., 2007) in VoiceSauce enables users to remove the amplifying effect of vowel formants on harmonic energy, and consequently compare the harmonic energy across different vowel qualities. However, we found that the formant correction formula is unsuitable for correcting harmonics for formants much lower than the harmonic frequency. Such a correction will result in a large boost in the corrected harmonic energy. In this tutorial, we will demonstrate the rationale and problems of the formant correction formula used in VoiceSauce, how to modify the formant correction formula in VoiceSauce, and how to add additional harmonic parameters to VoiceSauce.