Table 1.

Ten variables were measured in the EMG signal and the subglottal pressure signal.

Parameter	Explanation
Duration	Duration of the expiratory phase of the respiratory cycle during which the call is produced
Ratio (phasic/tonic)	Ratio of the duration of the increased phasic EMG activity and increased tonic EMG activity. For example in the call of Figure 1 it is 0.19. In a 22-kHz call it would 0. In a trill call it can exceed 1
TA EMG phasic	Average EMG activity during the increased phasic activity, determined by low-pass filtering (300 Hz) of the full-wave rectified signal
TA EMG (%swallowing)	EMG activity during the entire call relative to a maximum produced by this individual. The rectified signal during phonation was normalized to maximum EMG activity. The largest EMG activities were observed during swallowing when the animal was feeding or drinking
Ps mean	Mean positive subglottal pressure
Ps max	Maximum subglottal pressure
Ps symmetry	The symmetry of the subglottal pressure contour around the midpoint of the expiratory phase is calculated as the difference between the maximum subglottal pressure of the call and the average subglottal pressure of the respective half. The ratio of the numbers for the first and second half is determined
CV of Ps	Coefficient of variation of the positive pressure signal. CV is calculated from all the positive pressure values during the expiratory cycle during which the call was produced. In a long 22 kHz call with little pressure variation, CV is relatively small but it is large in a trill call with many small subglottal pressure fluctuations
# of bursts	Number of bursts during the phasic TA EMG activity
Phasic dur	Duration of the increased phasic TA EMG activity

See Figure 1 for further explanations.