Voice source characteristics in different registers in classically trained female musical theatre singers

Musical theatre singing typically requires females to use two vocal registers. Physiological differences between these registers, however, have not been explicated. Our investigation considered voice source and subglottal pressure Ps characteristics of these registers, here referred to as chest and head register. These were studied by inverse filtering the oral airflow recorded for a sequence of /pae/ syllables sung at constant pitch and decreasing vocal loudness in each register by seven female professional musical theatre singers. Ten equidistantly spaced Ps values were selected and the relationships between Ps and several parameters were examined; closed quotient Qclosed, peak-to-peak pulse amplitude Up-t-p, negative peak of the differentiated flow glottogram, i.e., the maximum flow declination rate (MFDR) and the normalised amplitude quotient (NAQ) [Up-t-p/ (T0*MFDR)] where T0 is the fundamental period. Ps was typically slightly higher in chest than in head register. As Ps influences the measured glottogram parameters, these were also compared at an identical Ps of 11 cm H2O. Results showed that for typical tokens MFDR and Qclosed were significantly greater while NAQ and Up-t-p were significantly lower in chest than in head. These observations can be explained if vocal fold thickness is assumed to be greater in chest register.