ACOUSTIC COUPLING IN PHONATION AND ITS EFFECT ON ...

29High-speed video is expected to supplement or replace stroboscopy in the assessmentof vocal function and promises to provide new insights of the relationships betweenvocal folds tissue motion and sound production [147,149].Aerodynamic assessment considers the use of a circumferentially vented pneumotachographmask [24] (also referred to as CV mask or Rothenberg mask) thatcaptures oral volume velocity (OVV) and intraoral pressure (IOP) within a bandwidthof approximately 0 Hz to 1.2 kHz [24]. In the clinical practice, however, thesesignals are used to obtain single-value descriptors such as mean airflow, subglottalpressure, glottal resistance, and phonation threshold pressure. A number of parameterscan be extracted when studying the AC airflow signal, including AC/DC ratio,open and closed quotient, minimum and peak flow, and maximum flow declinationrate (MFDR), among others. The MFDR, defined as the negative slope of the glottalairflow waveform, is of great interest in the assessment of vocal function, as it hasbeen related to vocal fold closing velocity and vocal fold trauma [25] and correlatedwith the radiated SPL for inertive vocal tract configurations [150]. In addition, itis suggested that AC flow signal assessment of vocal function can detect pathologieswhere, in some cases, acoustic assessment do not [98,110]. Furthermore, clinical studieshave shown that the AC flow parameters are one of the most salient measures toidentify vocal hyperfunction [25,40].Acoustic assessment of vocal function is widely used in the clinical practice. Typicalmeasures include sound level pressure (SPL), average fundamental frequency (F 0 ),jitter, shimmer, and harmonic-to-noise ratio. These measures are generally made fromsustained vowels and/or a passage reading. The parameters proposed in [12] (e.g.,H1-A1 and H1-A3, where H1 represents the amplitude of the first harmonic and A1and A3 the first and third formant spectral peaks) are sometimes used to corroboratebreathiness and other non-modal descriptions. Other similar measures include theharmonic richness factor (HRF) defined as the difference between the amplitude ofthe fundamental frequency and the sum of all other harmonics [151], and the differencein the amplitude of the first two harmonics (H1-H2) [27]. Jitter and shimmer,