Voice source differences between falsetto and modal registers in counter tenors, tenors and baritones.

Vocal registers are generally assumed to be associated with the voice source, i.e. the pulsating transglottal airflow. The waveform of this airflow was analysed by inverse filtering in professional singers, four counter tenors, five tenors, and four baritones singing the syllable [pae:] in soft, middle, and loud voice in modal and falsetto/counter tenor register. Subglottal pressure, estimated from the intra-oral pressure during the occlusion for the consonant [p], closed quotient, relative glottal leakage, and the relative level of the fundamental were analysed. The counter tenors used comparatively low subglottal pressures and mostly showed a closed phase in their flow glottogram waveform. For a given value of the closed quotient, the fundamental tended to be stronger in falsetto than in modal register. The observed voice source differences between the registers seem related to a greater vocal fold thickness in modal than in falsetto register.