Glottal Efficiency of Periodic and Irregular In Vitro Red Deer Voice Production

Two female red deer larynges were artificially phonated in an excised larynx setup by varying subglottal pressure as the independent parameter. The acquired data were annotated as periodic, subharmonic and irregular by means of the recently developed phasegram technique. Glottal efficiency was non-linearly dependent on subglottal pressure. Above 1 kPa subglottal pressure the glottal efficiency increased linearly by about 3.1 and 3.7 dB per kPa, respectively, in the two larynges. At subglottal pressures above 1.5 kPa the glottal efficiency of the irregular segments was in average about 2.5 to 3 dB greater than that of the periodic and subharmonic segments. The results of this pilot study suggest that an irregular sound production mechanism at higher subglottal pressures could. be a means to gain an energetic advantage in animal vocal communication when converting metabolic to acoustic energy.