bartholomew stated that a good operatic voice needs a concentration of energy around 3 khz ( 1 ) . he also mentioned that this concentration must be produced with a special resonator in the larynx or lower pharynx . he constructed long - term average spectra of normal speech and orchestral music with and without a solo singer 's voice ( 2 - 4 ) . he demonstrated the presence of a secondary peak of acoustic energy around the 2 - 3 khz region for operatic singing . he also found that the singer 's formant is a formant cluster of the third , fourth and fifth formants and that a prominent spectrum envelops the peak appearing in the vicinity of 3 khz in all vowel spectra sung by male singers and alto singers . a similar phenomenon observed in trained speakers has led investigators to examine the speaker 's ring . oliveira barrichelo et al . found that singers show more energy concentration in the singer 's formant / speaker 's ring region in both singing and spoken vowels ( 5 ) . furthermore , it was observed that the singers ' spoken vowel energy in the speaker 's ring area was significantly larger than that of untrained speakers . in a previous study , titze and jin showed that for trained tenors , in addition to the conventional singer 's formant in the region of 3 khz , another energy peak in the 8 - 9 khz region was present ( 6 ) . singers in other operatic voice ranges who produce vocal ringing are assumed to have the same peak in the singing and speaking voices . thus , the authors sought to investigate the energy peak in the singing voice around the 8 - 9 khz region and in the speaking voice around the 3 and 8 - 9 khz regions in 4 voice ranges of trained opera singers . we chose 15 tenors , 14 baritones , 7 sopranos and 5 mezzo sopranos in order to investigate the singer 's formant . after 1 yr , we chose another 10 tenors , 15 baritones , 15 sopranos and 10 mezzo sopranos in order to investigate the speaker 's ring . all subjects were enrolled at a music college , department of vocal music and they could reliably produce the head and chest registers . in the singer 's formant group , age ranged from 23.3 to 34 yr and the average period of vocal training in singers ' formant group was 4.6 yr for tenors , 5.4 yr for baritones , 8.8 yr for sopranos and 18 yr for mezzo sopranos . in the speakers ' ring group the age ranged from 21.6 to 31.2 yr and the training period was 7.9 yr in tenors , 6.3 yr in baritones , 9.4 yr in sopranos and 15.6 yr in mezzo sopranos . each subject was asked to produce a successive /a/ vowel for at least 3 sec at a high pitch ( tenors , g4 ; baritones , e4 ; sopranos , f5 ; and mezzo sopranos , c5 ) and a low pitch ( tenors , c3 ; baritones , d3 ; sopranos , d4 ; and mezzo sopranos , a3 ) and they were also asked to produce a sustained vowel /a/ as a usual speaking sound . the high pitch was produced in the head register and the low note in the chest register , as judged by a professor of music and a graduate of the conservatory . the singing and spoken vowels were initially recorded on a sony dat recorder tcd - d7 ( sony , tokyo , japan ) . the unidirectional dynamic microphone was used for data acquisition at the standard distance between voice and microphone of 17 cm . we adjusted the input level to the green led lights on the front panel of the csl external module in order to avoid overloading . the sound samples were analyzed with the long - term average ( lta ) power spectrum using the fft algorithm of the computerized speech lab ( csl , model 4300b , kay elemetrics , lincoln park , nj , usa ) . long - term average frequency spectra were computed with a short analysis window ( 64 points or 3.2 ms ) . the control group consisted of 15 male and 15 female adults who had no laryngeal abnormalities or abnormalities of articulation . age ranged from 24.5 to 32.4 yr , which was similar with that of the trained singer 's group . the control subjects were also asked to produce successive /a/ vowel sounds using their usual singing pitch ( male , g4 and c3 ; female , f5 and d4 ) and usual speaking techniques . statistical analysis was performed using the mann - whitney test of the statistical package for social sciences ( version 13.0 , spss , chicago , il , usa ) . data analysis included the evaluation of the difference in energy concentration along the frequency spectrum . 1 shows the energy levels of the singing vowel averages at a high pitch for each frequency analyzed for the tenor , baritone , soprano , mezzo soprano and control groups . a significant energy concentration was seen in the 2.2 - 3.4 khz region ( p<0.05 ) and 7.5 - 8.4 khz ( p<0.05 ) for the head registers of the tenors and baritones , respectively , compared to the untrained male control group ( fig . in addition , there were significant energy concentrations for the sopranos and mezzo sopranos compared to the untrained female control group in the 2.8 - 3.4 khz region ( p<0.05 ) . the sopranos showed significant energy concentration in the 7.8 - 8.4 khz region ( p<0.05 ) . however , the mezzo sopranos did not show energy concentration in the 8 - 9 khz region ( fig . 2 illustrates the energy levels of the singing vowel averages at a low pitch at each frequency analyzed for 4 categories of trained opera singers as well as the male and female control groups . similar to the head register sounds , a significant energy concentration was seen in the 2.2 - 3.1 khz region ( p<0.05 ) and the 7.8 - 8.4 khz region ( p<0.05 ) for the chest registers of the tenors and baritones compared to the untrained male control group ( fig . there were significant energy concentrations for the sopranos and mezzo sopranos compared to the untrained female control group in the 2.5 - 3.1 khz region ( p<0.05 ) and 7.8 - 8.4 khz ( p<0.05 ) ( fig . the average energy levels of spoken vowel /a/ for each frequency which are analyzed for 4 categories of the trained opera singers and male / female control groups are shown in fig . a significant energy concentration was seen in the 2.2 - 3.4 khz region ( p<0.05 ) for the spoken vowel /a/ for the tenors and baritones compared to the untrained male control group ( fig . there was a significant energy concentration for the sopranos compared to the untrained female control group in the 2.5 - 5.3 khz region ( p<0.05 ) and the 9 - 10 khz region ( p<0.05 ) . mezzo 
 sopranos showed significant energy concentration in the 2.2 - 3.7 khz region ( p<0.05 ) ( fig . voice characteristics are determined by the interactions of breathing mechanisms , the vibrating vocal folds and resonances of the vocal tract ( 7 ) . the classically trained singer strives to develop a singer 's formant that enhances the over all richness and ringing in his / her voice . the singer 's formant is characterized by an increase in signal intensity between the third and fourth formants . this allows audiences to hear the singer 's voice with amplification over the sounds of accompanying music ( 8) . the greatest harmonics peak between 2 and 4 khz is roughly the center frequency for the singer 's formant ( 2 ) . it makes the human voice easier to hear in the presence of a loud orchestral accompaniment ( 9 ) . many studies have described and analyzed the singer 's formant ( 1 - 4 , 7 ) . sundberg offered a physiological explanation , and he modeled the singer 's formant with a small resonator inside the vocal tract in the epilaryngeal region ( 4 ) . several researchers have made progress in the understanding of the speaker 's formant and ring ( 5 , 7 , 10 , 11 ) . recently , oliveira barrichelo et al . hypothesized that trained singers could carry their singing formant ability into normal speech ( 5 ) . they found that singers ' spoken vowel energy in the speaker 's ring area was significantly larger than that of untrained speakers . in this study , the authors investigated the energy peak in the singing voice around the 8 - 9 khz region and in the speaking voice around the 3 khz region in 4 categories of trained opera singers . we also found the energy peak in the 8 - 9 khz region in sopranos ' speaking sound . although we did not measure the sound pressure level during the recording of the singers ' voice using a dat recorder , we focused on the recording of the most outstanding voice as judged by a professor of music and a graduate of the conservatory . first , there was energy concentration around the 8 khz region in most trained singers ' singing voices . second , the speaking voice of 4 categories of trained opera singers significantly demonstrated more energy around the 3 khz region , and sopranos ' speaking voice also showed another energy peak in the 8 - 9 khz region . we postulate that both the head / chest register and the speaking sounds , when formed in the classically trained singing technique , are closely related to the formation of the singer 's formant / speaker 's ring . in addition , it seemed that the singers had a tendency to produce the spoken vowel in a singing fashion as previously described by stone et al . a significant finding of this study is that for trained operatic singers , in addition to the conventional singer 's formant in the region of 3 khz , another energy peak was observed in the region of 8 - 9 khz . this second peak was interpreted as the second resonance of the epilarynx tube ( 6 ) . we applied the formula that was derived for a uniform tube that was closed on one end ( the glottis ) and open on the other ( the aryepiglottic collar ) . this formula is f=(2n-1)c/4l where c is the speed of sound in the vocal tract ( 340 m / s ) , l is the length of the epilarynx tube ( 3 cm ) and letter n is 2 . use of this formula revealed a second resonance frequency at about 8.5 khz ( 6 ) . in this study , the authors found energy at around 8 khz in most trained singers ' singing voices and soprano ' speaking voices . although we did not measure the value in this study , there was the possibility that another energy peak could be theoretically present near the 15 khz . however , the energy level around the 8 - 9 khz region is about 20 - 30 db below that of singer 's formant region , suggesting that it may be beyond the range of perceived sound since the sensitivity of the human auditory system is also about 20 db lower around the 8 khz region instead of the 3 khz region . however , with other recording and amplification systems , where high frequency emphasis is given , a formant of 8 - 9 khz could reach perceptual significance ( 6 ) . it is thought that this second singers ' formant may contribute to their rich and ringing voice . . however , our findings suggest the possibility of a formerly unrecognized singer 's formant in the 8 - 9 khz region . the results of this study suggest that singing voices of opera singers and some of their speaking voices may show more energy concentration in the singer 's formant / speaker 's ring region compared to the control group . another energy concentration in the 8 - 9 khz region was observed in all opera singers ' singing vowel . we believe that this region is the second singer's / speaker 's formant which can contribute to singers ' rich voice .
objectiveswe previously showed that a trained tenor 's voice has the conventional singer 's formant at the region of 3 khz and another energy peak at 8 - 9 khz . 
 singers in other operatic voice ranges are assumed to have the same peak in their singing and speaking voice . 
 however , to date , no specific measurement of this has been made.methodstenors , baritones , sopranos and mezzo sopranos were chosen to participate in this study of the singer 's formant and the speaker 's ring resonance . 
 untrained males ( n=15 ) and females ( n=15 ) were included in the control group . 
 each subject was asked to produce successive /a/ vowel sounds in their singing and speaking voice . for singing , 
 the low pitch was produced in the chest register and the high notes in the head register . 
 we collected the data on the long - term average spectra of the speaking and singing voices of the trained singers and the control groups.resultsfor the sounds produced from the head register , a significant energy concentration was seen in both 2.2 - 3.4 khz and 7.5 - 8.4 khz regions ( except for the voices of the mezzo sopranos ) in the trained singer group when compared to the control groups . 
 also , the chest register had a significant energy concentration in the 4 trained singer groups at the 2.2 - 3.1 khz and 7.8 - 8.4 khz . for speaking sound 
 , all trained singers had a significant energy concentration at 2.2 - 5.3 khz and sopranos had another energy concentration at 9 - 10 khz.conclusionthe results of this study suggest that opera singers have more energy concentration in the singer 's formant / speaker 's ring region , in both singing and speaking voices . furthermore , another region of energy concentration was identified in opera singer 's singing sound and in sopranos ' speaking sound at 8 - 9 khz . 
 the authors believe that these energy concentrations may contribute to the rich voice of trained singers .