The mechanical properties of the lips are of crucial importance to the function of a brassudinstrument. The natural resonance modes must be able to usefully interact with theudinstrument air column in order to sustain oscillations. Mechanical frequency responsesudof human and arti cial lips used to play a brass instrument were measured using audhigh-speed digital video technique in an attempt to classify the true nature of the lipreed.udThe results revealed the presence of at least two lip modes that exhibited theudcharacteristic outward-inward striking behaviour seen in many in vitro replica lip-reedudmeasurements. The Q-values of the human lip resonances were considerably lower thanudthose seen for the replica lips. Transverse mechanical response measurements were alsoudperformed on an in vitro lip-reed to investigate the coupling between the outward andudinward striking modes. The two dimensional motion of the lips during full oscillationsudwas investigated. It is shown that a computational four degree-of-freedom model wouldudbe required to fully simulate the observed mechanical motion.udThe uduid behaviour downstream from an in vitro vocal fold model was investigatedudusing particle image velocimetry (PIV). A `free jet' con guration with no downstreamudacoustical coupling was rst investigated. The measurements revealed an unsteadyudglottal jet udow, consisting of a high velocity jet core, a transitional region of high jetuddeceleration and a turbulent mixing region. The jet was consistently skewed at anglesudto the glottal centreline, and appeared to oscillate back and forth across the centrelineudduring the glottal cycle. The behaviour of the jet core was investigated in detail. Audtemporal asymmetry was observed in the mean velocity across the jet core such that theudhighest jet velocities were encountered during the closing phase of the vocal folds. Theudoverall jet behaviour also showed a strong turbulent asymmetry between the openingudand closing phases. High levels of vorticity and turbulent motion encountered duringudthe closing phase were associated with the deceleration of the jet.udThree vocal fold con gurations that included static replicas of the ventricular bandsudwere nally investigated with the aim of characterising the aerodynamic interactionudbetween the ventricular bands and the vocal folds. A marked e ect on the glottal jet wasudobserved for all con gurations. The most physically realistic con guration appeared toudstabilise the glottal jet, leading to a reattachment of the jet to the ventricular bands anduda subsequent secondary udow separation from the downstream end. The implications ofudthe aerodynamic interaction is discussed, with particular note to its possible relevanceudto the lip-reed and mouthpiece interaction in brass playing.
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