Lower Vocal Tract Morphologic Adjustments Are Relevant for Voice Timbre in Singing

Abstract

The vocal tract shape is crucial to voice production. Its lower part seems particularly relevant for voice timbre. This study analyzes the detailed morphology of parts of the epilaryngeal tube and the hypopharynx for the sustained German vowels /a/, /e/, /i/, /o/, and /u/ by thirteen male singer subjects who were at the beginning of their academic singing studies. Analysis was based on two different phonatory conditions: a natural, speech-like phonation and a singing phonation, like in classical singing. 3D models of the vocal tract were derived from magnetic resonance imaging and compared with long-term average spectrum analysis of audio recordings from the same subjects. Comparison of singing to the speech-like phonation, which served as reference, showed significant adjustments of the lower vocal tract: an average lowering of the larynx by 8 mm and an increase of the hypopharyngeal cross-sectional area (+ 21.9%) and volume (+ 16.8%). Changes in the analyzed epilaryngeal portion of the vocal tract were not significant. Consequently, lower larynx-to-hypopharynx area and volume ratios were found in singing compared to the speech-like phonation. All evaluated measures of the lower vocal tract varied significantly with vowel quality. Acoustically, an increase of high frequency energy in singing correlated with a wider hypopharyngeal area. The findings offer an explanation how classical male singers might succeed in producing a voice timbre with increased high frequency energy, creating a singer‘s formant cluster.

Multidimensional Timbre Spaces of Cochlear Implant Vocoded and Non-vocoded Synthetic Female Singing Voices

“…Perceptually, differences in glottal excitation source spectral slope are believed to be related to the vocal quality dimension of fluty vs. brassy (Sundberg et al, 2004), while differences in overall resonance frequencies of the vocal tract have been shown to predict perception of Western classical voice categories such as mezzo-soprano and soprano (Cleveland, 1977;Dmitriev and Kiselev, 1979;Erickson, 2004). A clustering of the 3rd, 4th, and 5th resonances, known as the singer's formant cluster (Sundberg, 1974), is associated with perception of ring in the voice (Ekholm et al, 1998) and may be related to behavioral modification of vocal tract configuration in either the hypopharyngeal or epilaryngeal area (Sundberg, 1974;Mainka et al, 2015;Story, 2016).…”

“…A detailed description of these factors is beyond the scope of this paper; however, as a starting point, the reader is directed to Johan Sundberg's chapter in The Psychology of Music (Sundberg, 2013). Generally, these factors may be described as (a) variations across pitch and loudness (Echternach et al, 2016), (b) variations based on singing style (Sundberg et al, 1993Thalén and Sundberg, 2001;Stone et al, 2003;Björkner, 2008;Borch and Sundberg, 2011;Bourne and Garnier, 2012;Guzman et al, 2015;Sundberg and Thalén, 2015;Yang et al, 2015;Bourne et al, 2016;Hallqvist et al, 2017), (c) variations based on vocal register (Titze, 1994;Sundberg and Kullberg, 1999;Sundberg and Högset, 2001;Roubeau et al, 2009), and (d) variations based on the need for a singer's formant cluster (Sundberg, 1974(Sundberg, , 1994(Sundberg, , 2001(Sundberg, , 2013Dmitriev and Kiselev, 1979;Bloothooft and Plomp, 1986;Barnes et al, 2004;Johnson and Kempster, 2011;Mainka et al, 2015;Story, 2016). Thus, while speakers may keep a relatively constant glottal excitation source spectral slope and exhibit relatively small variations in VTL during speech, successful professional singers must learn to purposefully modify both the glottal excitation source and the vocal tract filter, resulting in vocal productions that are physiologically, acoustically, and perceptually much different from those of speech in many cases.…”

Relating Estimated Cyclic Spectral Peak Frequency to Measured Epilarynx Length Using Magnetic Resonance Imaging

“…Situated between the glottis and the pharynx, the epilarynx is a region of the lower vocal tract (VT) that plays an important role in speech production, regulating vocal loudness and coloring timbre in addition to carrying speaker-specific information [1,2,3,4]. Though typically overlooked in many speech processing applications, the resonance pattern of the lower VT cavities (epilarynx and piriform fossa) shapes the speech spectrum in a prominent and largely static way, occupying a frequency range above 3kHz that avoids highly dynamic lower formants (F1, F2) [1,2].…”

“…1:3) [4,17]. The precise means of quantifying these area measurements is also not obvious, as shown in [4].…”

“…Though analyses of the epilarynx morphology have recently become more detailed with access to high-resolution 3D MRI, as in [4,15], examination of the observable (i.e. not simulated) acoustics is typically limited to coarse measurements of longterm average spectral energy in a broad frequency range (e.g.…”