The role of vocal tract and subglottal resonances in producing vocal instabilities

Abstract

During speech and singing, the vibrating vocal folds are acoustically loaded by resonant ducts upstream (the trachea) and downstream (the vocal tract). Some models suggest that the vocal fold vibration (at frequency f) is more stable at frequencies below that of a vocal tract resonance, so that the downstream load is inertive (mass-like). If so, vocal fold vibration might become unstable when f and resonance frequencies "cross over" and the load varies rapidly in phase and magnitude. In one experiment, singers produced a slow diphthong at constant pitch, thus shifting the first tract resonance R1 across fixed f. In another, pitch glides took f across the tract and subglottal resonances. Few instabilities occurred when singers could change lip geometry and thus alter R1. This suggests that avoiding resonance crossings can aid vibrational stability. In experiments in which R1 was constrained using a mouth ring, instabilities occurred at frequencies above R1. When subjects sang into an acoustically infinite pipe, which provided a purely resistive load at the lips, R1 was eliminated. Here, instabilities were reduced and concentrated near the lower limit of the head voice.

Modal Locking Between Vocal Fold Oscillations and Vocal Tract Acoustics

“…These works reveal a consistent picture of the existence of perturbations caused by resonant loads, and this phenomenon has also been detected experimentally in [17] using speech recordings, in [18] using simultaneous recordings of laryngeal endoscopy, acoustics, aerodynamics, electroglottography, and acceleration sensors, and in [19] using simultaneous speech, electroglottography and accelerometer recordings combined with separate resonance estimation measurements.…”

“…A similar pattern can be seen in the speech spectrograms given in [17, Figure 5], [16,Figure 4], as well as in the vowel glide samples in the data set of [3]. The pitch trajectory and speech spectrogram in [19,Figure 4] also show locking but no release. A similar locking behaviour can also be interpreted to lie behind the experimental results shown in [12,Figures 10b and 13b], and it also tends to emerge in model simulations even if the acoustic feedback is realised in different manner; see, e.g., [14,Figures 13 and 14] and [69, Figure 6].…”

“…After the release of f o the glottal pulse characteristics return gradually to the feedback free trajectories, except for ✓. The sudden as given in equations (18) and (19). For given model 735 parameter values, falling glides exhibit more fluctua-736 tions in glottal pulse parameters at the locking event 737 and the perturbation lasts longer.…”

Subglottal resonances of American English speaking children

“…To capture the speech and subglottal acoustics of the participants, recordings were made using a free-standing SHURE PG27 microphone (Shure, Niles, IL) and a K&K Sound HotSpot accelerometer (K&K Sound Systems, Coos Bay, OR) while participants sat in a double-walled sound attenuating booth. The accelerometer is advertised to have a flat magnitude response for up to 15 kHz, and Wade et al (2017) verified that the magnitude response was at least flat in the range of 350-2000 Hz. Any deviation from the flat response of the accelerometer would only affect the magnitude of a resonance but not the frequency.…”

Soprano singing, with and without resonances

“…The study described here is part of a larger study 5 of eight volunteer female singers whose formal vocal training and experience is summarised in Table 1. All were speakers of Australian English.…”