title: 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 fo) 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 foand 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 fo. In another, pitch glides took foacross 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.
authors.affiliation: School of Physics, University of New South Wales, Sydney, New South Wales 2052, Australia.
authors.forename: Laura
authors.initials: L
authors.lastname: Wade
authors.affiliation: School of Physics, University of New South Wales, Sydney, New South Wales 2052, Australia.
authors.forename: Noel
authors.initials: N
authors.lastname: Hanna
authors.affiliation: School of Physics, University of New South Wales, Sydney, New South Wales 2052, Australia.
authors.forename: John
authors.initials: J
authors.lastname: Smith
authors.affiliation: School of Physics, University of New South Wales, Sydney, New South Wales 2052, Australia.
authors.forename: Joe
authors.initials: J
authors.lastname: Wolfe
mesh_terms: D061725:Accelerometry / Q000379:methods; D000162:Acoustics; D000328:Adult; D004568:Electrodiagnosis / Q000379:methods; D005260:Female; D006801:Humans; D063346:Singing; D013018:Sound Spectrography; D014732:Vibration; D014827:Vocal Cords / Q000502:physiology*; D014833:Voice Quality; D055815:Young Adult