Vocal membranes lower the phonation threshold pressure in rhesus macaques (Macaca mulatta)

The vocal membrane is present in a wide range of species including non-human primates. It has been a matter of great interest how this small tissue contributes to the animal vocalizations and its evolutionary loss facilitated the speech communication in humans. There has been a theoretical study (Mergell et al., 1999), which predicted that the vocal membranes make the animal vocalizations more efficient by lowering the phonation threshold pressure. To examine the theoretical prediction, excised larynx experiments have been carried out for rhesus macaques (Macaca mulatta). Comparison of the larynges before and after surgical removal of the vocal membranes revealed that the phonation threshold pressure was indeed lower and, consequently, the vocal efficiency was higher in the presence of the vocal membranes. Irregular chaotic oscillations were also observed for some larynges with the vocal membranes. , From two fresh cadavers of adult female macaques (#1, #2), the laryngeal samples were extracted, flash-frozen in liquid nitrogen, and stored at -80 degrees. The frozen samples were thawed shortly before the excised larynx experiments, which were performed under two conditions: (A) in the presence of the vocal membranes and (B) in the absence of the vocal membranes.
Under both conditions, individual larynx was mounted on a vertical tracheal tube. The flow rate of humid air (about 37 degrees; 100 % relative humidity) that comes from an air pump (SilentAirCompressor Sc820, Hitachi Koki Co., Ltd., Tokyo, Japan) was controlled by a pressure regulator (10202U, Fairchild, Winston-Salem, NC) and a digital mass flow controller (CMQ-V, Azbil, Santa Clara, CA). To induce vocal fold vibrations, the glottal air space was narrowed by manually adducting the arytenoid cartilages. Once the adjustment was made, positions of the arytenoid cartilages were fixed by a surgical suture. This configur..., , # Vocal membranes lower the phonation threshold pressure in rhesus macaques (Macaca mulatta)

[https://doi.org/10.5061/dryad.73n5tb356](https://doi.org/10.5061/dryad.73n5tb356)

## Description of the data and file structure

The data is composed of 6 data sets, named as \"macaque*_*.tar.gz\".

\"macaque{1,2}_*.tar.gz\" give the data recorded from macaques #1 and #2, respectively.

\"macaque*_vm.tar.gz\" are for condition (A1), in which vocal folds did not show a strong vibration and only the vocal membranes oscillated.

\"macaque*_vmvf.tar.gz\" are for condition (A2), in which both vocal folds and membranes oscillated simultaneously.

\"macaque*_vf.tar.gz\" are for condition (B), in which vocal folds oscillated in the absence of vocal membranes.

Each file (\".tar.gz\") includes 10 sets of microphone signals (physical unit: voltage) and subglottal pressure signals (physical unit: Pa) (\"macaque*.csv\"), microphone sounds (\"macaque*.wav\"), and high-speed filming data (\"macaque*.mp4\").
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