19 th INTERNATIONAL CONGRESS ON ACOUSTICS MADRID, 2-7 SEPTEMBER 2007 OBSERVATION OF SUBHARMONIC VOICES

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1 19 th INTERNATIONAL CONGRESS ON ACOUSTICS MADRID, 2-7 SEPTEMBER 2007 OBSERVATION OF SUBHARMONIC VOICES PACS: Rs Sakakibara, Ken-Ichi 1 ; Imagawa, Hiroshi 2 ; Kimura, Miwako 2 ; Tokuda, Isao 3 ; Tayama, Niro 4 1 Department of Communication Disorder, Health Sciences University of Hokkaido; 2jo-5chome, Ainosato, Kita-ku, Sapporo, Hokkaido, , Japan; kis@hoku-iryo-u.ac.jp 2 Department of Otolaryngology, University of Tokyo; 7-3-1, Hongo, Bunkyo-ku, Tokyo, , Japan: imagawa@m.u-tokyo.ac.jp; mkimu-tky@umin.ac.jp 3 School of Information Science, Japan Advanced Institute of Science and Technology; Ishikawa, , Japan; isao@jaist.ac.jp 4 International Medical Center of Japan; , Toyama, Shinjuku-ku, Tokyo, , Japan; ntayama@imcj.hosp.go.jp ABSTRACT Subharmonic voices are observed in various singing styles in the world. One of the variations of Strohbass (vocal fry), Kargyraa in throat singing and growl voices in Jazz are representatives of subharmonic voices. These subharmonic voices reveal perceptual similarities and it is difficult to distinguish one from the others. However, their phonatory maneuvers are different. This paper examined production mechanisms of subharmonic voices and acoustical characteristics. 1 Introduction Subharmonic voice is a voice in which F 0 /2 (in general, F 0 /n for n N) is perceived as pitch, as well as the fundamental frequency F 0 of original tone. Subharmonic voices are frequently found in pathological voices because of lateral and longitudinal asynchronous vocal fold vibrations which are caused by structural changes of the vocal fold tissues. On the other hand, even in normal voices, subharmonic vibratory patterns of the vocal folds appear mostly in low-power oscillation, such as in vocal fry. In singing voices, subharmonic voices are also observed in various styles in the world. One of the variations in Strohbass (vocal fry), Kargyraa in throat singing, and growl voices in Jazz are representatives of subharmonic voices [12, 13, 16]. These sounds may be perceived equivalently as subharmonic or rough. However, their production mechanisms are different. In the human larynx, there is a three-tiered sphincter comprising the vocal folds, the ventricular folds, and the aryepiglottic sphincter [11]. Besides the vocal and ventricular folds, the aryepglottic constriction caused by the approximation of the tubercle of the epiglottis (anterior), aryepiglottic folds (lateral), and arytenoids (posterior) may generate sustained vibration in the supraglottal region of the larynx (Figure 1). Pyriform sinus Epiglottis Aryepiglottic fold Ventricular fold Laryngeal ventricle Vocal fold Figure 1: Coronal view of the human larynx, as seen from behind 1

2 In vocal fry, the approximation of the ventricular folds are observed, however, only the vocal folds vibrate and contribute to produce its sound. On the other hand, in karygraa, besides the vocal folds, the ventricular folds vibrate, and in growl, aryepiglottic folds vibrate. These supraglottal vibrations contribute to produce their subharmonic sounds. In this paper, we summarize the subharmonic vibratory phenomena and examine them from the physiological viewpoint. 2 Vocal fry (vocal fold phonation) The vocal fry phonation reveals very complicated variations in its vibratory patterns: (1) periodic with small O q ; (2) periodic and subharmonic (double and triple); (3) aperiodic or a very long period. The variation of phonatory phenomena makes it difficult to effectively extract the common acoustic characteristics. The F 0 of vocal fry approximately ranges from 20 to 80 Hz, with its mean about 50 Hz, and there is no significant difference between male and female. The airflow and air pressure in vocal fry is smaller than in modal [3, 5, 9, 10, 12, 18]. By using an X-ray laminagraph, laryngeal configuration for vocal fry were observed [1]. It resulted that the vocal folds are very thick, the ventricular fold contacted on the vocal fold, and the space of the laryngeal ventricle is small. Our fibrescopic observation of the laryngeal configuration during vocal fry phonation supports their results (Figure 2). However, vocal fry has variation in its phonatory pattern and, as we will discuss later, phonations with supraglottal structure vibration have perceptual similarities with vocal fry. Therefore, further verification of their results and careful physiological investigation are required. Some styles of folks music in Russia and Papua New Guinea, and the onset of certain special musical expression (e.g. in ballads of R&B music) are examples of singing in which vocal fry is used. Figure 2: Two different fibrescopic images of the laryngeal configuration in vocal fry 3 Vocal-ventricular phonation Kargyraa In some singing styles, ventricular fold vibration is observed. Throat singing is very representative of such styles. Throat singing is the traditional singing found around the Altai mountains. Khöömei in Tyva, Khöömij in Mongolia, and Kai in Altai are its representatives. In throat singing, two different phonation manners are used. One is called a drone voice, which is used as a basic voice for singing with whistle-like high overtone. The drone voice is perceptually analogous to so-called Damigoe, which is a kind of pressed-type voice used in some Japanese traditional singing, such as Naniwabushi. Another is called a kargyraa voice which is perceptually subharmonic[16]. A similar style is also found in the Tibetan Buddhists chants [17]. In both the drone and kargyraa voices, overall constriction of the supraglottal structure of the larynx was commonly observed. The constriction in kargyraa is looser than that in drone. In both voices, the inside edge of the vibrating portion is presumably the ventricular fold [16]. The supraglottal constriction makes direct observation of vocal fold vibrations difficult, especially in drone. However, by observing the EGG waveforms, high-speed digital images, and physical model simulation [14], we can reasonably state that both the vocal and ventricular folds vibrated. In drone, the period of the ventricular fold vibration was equal to that of the vocal fold vibration detected 2

3 from the EGG waveform. In kargyraa, the vibration of the ventricular folds was double periodic to that of the vocal folds. Vibration of the vocal folds was observed during the open period of the ventricular fold vibration (subharmonic). The period of the ventricular fold vibration estimated from the high-speed images and EGG were equal to the period of the sound waveform [7, 12, 16]. The vibration of the ventricular folds clearly contributes to the generation of subharmonic voice (Figures 3, 4). Figure 3: The fibrescopic high-speed images in kargyraa, by male Khöömei singer. Frame rate: 4/4500 s. Amplitude Less contact area Figure 4: Laryngeal flow obtained by inverse-filtering (left) and EGG waveform (right) for 40 ms in kargyraa, by male throat singer. (A1= 55 Hz) 4 Vocal-aryepiglottic phonation Growl The term growl is originally referred to as low-pitched sounds uttered by animals, such as dogs, or similar sounds by humans, and therefore is mainly described by auditory-perceptual impression. Growl is widely observed in singing as well as in shouting and aroused speech. The growl phonation has been also referred to as the phonation observed in some singing styles, such as the jazz singing style of Louis Armstrong (Satchmo s voice quality revealed roughness in the vocal fold level, however, he often used growl) and Cab Calloway, [4, 6]. Many jazz, blues, and gospel singers often use growl in a similar manner. Besides such pop musics from North America, growl styles are widely found in pop music of other areas: in Brazil, samba singers, and in Japan, Enka (a popular emotive style) singers, employ it frequently. Some singers use growl extensively through a song, while others use it as a vocal effect for expressive emphasis. In ethnic music, one of the most prominent use of growl is found in umngqokolo, which is a vocal tradition of the Xhosa people in South Africa [19]. In Japanese theatre, Noh percussionist s voice, Kakegoe, may present growl at the beginning of phonation. We observed laryngeal movements in growl directly and indirectly by simultaneous recording of high-speed digital images, EGG (Electroglottography) waveforms, and sound waveforms. The high-speed digital images were captured at 4500 frames/s through a endoscope inserted into the mouth cavity of a singer. Sound and EGG waveforms were sampled at 12 b/s and 18 khz sf [13]. In growl phonation, the aryepglottic region is compressed antero-posteriorly, and the tubercle of the epiglottis and the arytenoid cartilages come into contact (Figure 5). This antero-posterior compression is in good agreement with the lateral view of growl phonation in [2, 13]. Two-sided chinks generated by the contact of the epiglottic tubercle and arytenoids were observed. Each chink is surrounded by the epiglottis, arytenoid, and aryepiglottic fold. In some cases, both aryepiglottic folds vibrate in almost same phase (Figure 7), and in other cases, the phases of both seem to be slightly different. Furthermore, in some cases, the vibration of the aryepiglottic folds is unstable and seems to be aperiodic. 3

4 Figure 6 shows the sound waveform (top), EGG waveform (bottom, ordinate corresponds to total contact area of the larynx), and Figure 7 shows high-speed images. Vertical lines in the sound and EGG are synchronous to the last frames in each column of the high-speed images. The vibrations of the aryepglottic folds are observed in the high-speed images. In this case, the aryepiglottic fold vibration is likely to be periodic and the vibration of each side is mostly synchronous. From the EGG and sound waveform, it is reasonable to conclude that the vocal folds vibrate half-periodically to the aryepiglottic fold vibration. This vibration pattern of the vocal and aryepiglottic folds is same as the vocal-ventricular phonation, such as kargyraa, with F 0 /2. The period-double vibration of the aryepiglottic folds generates subharmonics. Neither the vocal nor ventricular folds were directly observed because the aryepiglottic folds were strongly constricted. Therefore, it is difficult to prove whether the vocal and ventricular fold vibrate or not. However, we conclude that the vocal and aryepiglottic folds vibrate and ventricular folds do not. The basis of this conclusion is as follows. Smooth transition from modal to growl is frequently achieved by various singers and the subjects, therefore, it is reasonable to claim that, in growl, the vocal folds vibrate at almost opposite phases. To take account of the delay of the sound to the EGG, we consider that the maximal excitation of sound and the shape of the EGG waveform were mainly due to the vocal fold vibration. we also consider, if all three folds had simultaneously vibrated, the phases of their vibration would most likely have been different from each other by aerodynamical constraint. Arytenoid Epiglottis Figure 5: Aryepiglottic region in growl, as seen from above. Upper part is posterior Pressure frame # Contact Area Figure 6: Sound (top) and EGG (bottom) waveforms in growl Figure 7: High-speed images of growl. In images, frame step is 1/4500 ms. 4

5 Discussions and Conclusions Both in vocal-ventricular and -aryepiglottic phonations, supraglottal structures in the larynx vibrate, as well as vocal folds, and contribute to the subharmonic oscillation. The mechanism of the supraglottal constriction is still controversial. The supraglottal constriction is widely considered to be caused by an activity of the aryepiglottic and thyroepiglottic muscles, however, from our physiological observations and previous histological observation of the supraglottal muscles [8, 15], the constrictions of the aryepiglottic and ventricular folds are presumably caused by different mechanisms. The power of the subharmonics in growl is seemingly lower than in kargyraa, but further analysis is needed to clarify this. Perceptual evaluation of differences among various subharmonic phonations, such as growl, kargyraa, and vocal fry, will be addressed as future work. Analysis of other perceptually similar singing styles, such as Sardinian singing, will also be addressed as future work. Acknowledgements A part of this study was supported by SCOPE ( ) of Ministry of Internal Affairs and Communications (MIC), Japan. References [1] E. L. Allen and H. Hollien. A laminagraphic study of pulse (vocal fry) register phonation. Folia Phoniat., 25: , [2] S. Araújo and L. Fuks. Prácticas vocais no samba carioca: un diálogo entre a acústica musical e a etnomusicologia. In N. M. Claudia, T. M. Refnanda, and T. Elizabeth, editors, Ao encontro da Palavra Cantada: poesia, música e voz, pages Viveiros de Castro Ltda., [3] M. Blomgren, Y. Chen, M. L. Ng, and H. R. Gilbert. Acoustic, aerodynamic, physiologic, and perceptual properties modal and vocal fry registers. J. Acoust. Soc. Am., 103(5): , [4] J. C. Catford. Fundamental Problems in Phonetics. Edinburgh Univ. Press, [5] D. G. Childers and C. K. Lee. Vocal quality factors: analysis, synthesis, and perception. J. Acoust. Soc. Am., 90(5): , [6] J. H. Esling. Pharyngeal consonants and the aryepiglottic sphincter. J. International Phonetics Association, 26(2):65 88, [7] L. Fuks, B. Hammarberg, and J. Sundberg. A self-sustained vocal-ventricular phonation mode: acoustical, aerodynamic and glottographic evidences. KTH TMH-QPSR, 3/1998:49 59, [8] M. Kimura, K.-I. Sakakibara, H. Imagawa, R. Chan, S. Niimi, and N. Tayama. Histological investigation of the supra-glottal structures in human for understanding abnormal phonation. J. Acoust. Soc. Am., 112(5):2446, [9] S. Kiritani. High-speed digital image recording for observing vocal fold vibration. In Voice Quality Measurement. Singular Publ., [10] S. Niimi and M. Miyaji. Vocal fold vibration and voice quality. Folia Phoniatr. Logop., 52:32 38, [11] J. J. Pressman. Sphincters of the larynx. A. M. A. Arch. Otolaryngol., 59(2): , [12] K.-I. Sakakibara. Production mechanism of voice quality. J. Phonetic Soc. Jpn., 7(3):27 39, [13] K.-I. Sakakibara, L. Fuks, H. Imagawa, and N. Tayama. Growl voice in pop and ethnic styles. In Proc. International Symposium on Musical Acoustics 2004, [14] K.-I. Sakakibara, H. Imagawa, S. Niimi, and N. Osaka. Synthesis of the laryngeal source of throat singing using a 2 2-mass model. In Proc. ICMC 2002, pages 5 8, [15] K.-I. Sakakibara, H. Imagawa, S. Niimi, and N. Tayama. Physiological study of the supraglottal structure. In Proc. International Conference on Voice Physiology and Biomechanics, [16] K.-I. Sakakibara, T. Konishi, K. Kondo, E. Z. Murano, M. Kumada, H. Imagawa, and S. Niimi. Vocal fold and false vocal fold vibrations and synthesis of khöömei. In Proc. ICMC 2001, pages , [17] H. Smith, K. N. Stevens, and R. S. Tomlinson. On an unusual mode of chanting by certain Tibetan Lamas. J. Acoust. Soc. Am., 41(5): , [18] R. L. Whitehead, D. E. Metz, and B. H. Whitehead. Vibratory patterns of the vocal folds during pulse register phonation. J. Acoust. Soc. Am., 75(4): , [19] H. Zemp, Ed. Les voix du monde une anthologie des expressions vocales. 3 vol. CDs with book, CNRS/Musée de l Homme, CMX