# Electroglottographic Analysis of the Voice in Young Male Role of Kunqu Opera
## 2 Materials and Methods  
Two male national actors of Kunqu Opera (YM1 and YM2 for short) volunteered as subjects. The ages of YM1 and YM2 were 45 and 27 years, respectively, when the signals were collected. Their professional experiences were 27 and 9 years, respectively. Neither of them smoked or had a history of vocal cord disease. Both singers sang four songs (16 min), recited a section of stage speech (2 min) as they would on stage after a warm-up exercise for about 1 min, and read the lyrics of the songs and stage speech (3 min) in a modal voice. Two of the songs were for [PERSON] and were the South song, and the other two songs were for [PERSON] and were the North song.  
Both singers were recorded in a quiet living room, of a size of about 4 \(\times\) 5 \(\times\) 3 m\({}^{3}\). Audio was picked up by a Sony Electret condenser microphone placed off axis at a measured distance of 15 cm from the mouth. Sound pressure level (SPL) calibration was carried out by recording a 1000-Hz tone, the SPL of which was measured at the recording microphone by means of a TES-52 sound level meter (TES Electrical Electronic, Corp., Taipei, China). The EGG signal was collected by an EGG system (Electroglottograph Model 6103; Kay, Montvale, NJ, USA). The signals were simultaneously recorded and digitized on 16 bits at a sampling frequency of 20 kHz and recorded on dual channel wav files into ML880 PowerLab system. The equivalent sound levels for reading lyrics, singing, and stage speech were 73, 89, and 92 dB (A) for YM1 and 73, 88, and 93 dB (A) for YM2, respectively [26].  
The signals were divided into characters. The audio and EGG signals were analyzed character by character using the VoiceLab 1.0 [27] automatically. The SPL values were extracted from the audio signals and calibrated to 0.3 m in order to make an easier comparison with the previous study. The contacting and the contacting events were approximated using the commonly used 35% of the EGG amplitude criterion [16; 23; 28], which is advantageous when vocal addition is to be detected. Three phonatory parameters were calculated: (1) \(f_{o}\), (2) EGG CQ (abbreviated as CQ), and (3) EGG SQ (abbreviated as SQ). The extracted data from each character were stratified by sampling into 30 data, since the duration of the character varied a lot. The song and the stage speech did not contain all speech sounds, but did contain most vowels of the language. The sample size in EGG cycles was 12,150 (YM1's singing), 4350 (YM1's stage speech), 11,400 (YM2's singing), and 3870 (YM2's stage speech). Statistical analyses were completed using SPSS 18. Since the data did not comply with the normal distribution, and the test of homogeneity of variances was significant (\(p<0.05\)), and the distributions of the EGG parameters were compared by Mann-Whitney U tests.  
Previous research indicated that the long-term-average spectrum of a YM role showed a large standard deviation, which implies a great variation of voice timbre [2]. To classify the phonation types, the EGG parameters were clustered by k-means method [16; 29]. When clustering in three dimensions, at least two clusters in each dimension are needed to differentiate between high and low values. Hence, if the parameters vary independently of one another, then at least eight centroids may be needed. On the one hand, if the parameters of the two centroids in the clustering results are very close, they are considered to be of the same phonation type. On the other hand, the phonation types were determined consulting both parameter properties and characteristics of the waveform. For the purpose of discussing waveforms, the modal voice from reading lyrics was presumed as the neutral  
Figure 1: The landmarks in the EGG signal.  
-phonon state. The phonation types were determined on the basis of the relationships between their EGG parameters and modal voice's EGG parameters.