Tag Archives: acoustics

Ken-Ichi Sakakibara*1, Tomoko Konishi, Emi Zuiki Murano*2, Hiroshi Imagawa*2, Masanobu Kumada*3, Kazumasa Kondo*4, and Seiji Niimi*5 : Observation of Laryngeal Movements for Throat Singing Vibrations of two pairs of folds in the human larynx, JAPAN


First Pan-American/Iberian Meeting on Acoustics, Cancun


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Observation of Laryngeal Movements for Throat Singing 
Vibrations of two pairs of folds in the human larynx

Ken-Ichi Sakakibara*1, Tomoko Konishi, Emi Zuiki Murano*2, Hiroshi Imagawa*2, Masanobu Kumada*3, Kazumasa Kondo*4, and Seiji Niimi*5 

*1 NTT Communication Science Laboratories, 3-1, Morinosato Wakamiya, Atsugi-shi, 243-0198, Japan
http://www.brl.ntt.co.jp/people/kis/ ,kis@brl.ntt.co.jp or k_i_s@hotmail.com 
*2 The University of Tokyo, Japan
*3 National Rehabilitation Center for the Disabled, Japan
*4 Asian University, Japan
*5 International University of Health and Welfare, Japan

Popular version of paper 2pMUa1
Presented Tuesday Afternoon, December 3, 2002
144th ASA Meeting, Cancun, Mexico


1. Singing voices of the world

In the world, there are various styles of singing. These variations in voices are mainly associated with variations in timbre. Such diversity of singing voices might have arisen due to cultural diversity such as climate, geography, language, racial physical feature, religion, musical structure, and so on. As a matter, we can find considerable differences between European traditional or classical singing voice, such as bel canto and German lied, and the Asian traditional pressed singing voices, such as throat singing around the Altai mountains, Japanese Youkyoku, and Korean Pansori. For instance, European traditional singing styles were developed as a result of performing in stone-made acoustical environment. Therefore, it requires constant timbre. On the other hand, most Asian singing styles were developed as result of performing in acoustical environment of softer material such as wood and mud. Therefore, it requires a rich and varied timbre. It’s possible to infer that singing styles and music structures (polyphonic in Europe and homophonic in Asia) have evolved by interacting with each other. Here, we study throat singing, which is one of the most sophisticated styles of pressed-type singing voices, and how its laryngeal voice is generated.

2. Throat singing

Throat singing is the traditional singing style of people who live around the Altai mountains. Khöömei in Tyva and Khöömij in Mongolia are representative styles of throat singing. Throat singing is sometimes called biphonic singing, or overtone singing because two or more distinct pitches (musical lines) are produced simultaneously in one tone. One is a low sustained fundamental pitch, called a drone, and the second is a whistle-like harmonic that resonates high above the drone. Sometimes throat singing mean wider styles including all the biphonic singing styles not restricted to the styles around the Altai mountains: e.g. Inuit, Xhosa, and so on. But here we use the term “throat singing” for the common styles around the Altai mountains: Khöömei, Khöömij, Kai in Altai, and so on.

The production of the highly pitched overtone of throat singing is mainly due to the pipe resonance of the cavity from the larynx to the point of articulation in the vocal tract, which appear as the 2nd formant in its sound spectrum. On the other hand, the laryngeal voice of throat singing has a special pressed timbre and supports the generation of the overtone.

The laryngeal voices of throat singing can be classified into two voices: (i) squeezed voice (soundfile); and (ii) kargyraa voice ( soundfile). based on the listener’s impression, acoustical characteristics, and the singer’s personal observation on voice production. The pressed voice is the basic laryngeal voice in throat singing and used as drone. The equivalent voice is used in Japanese Naniwabsuhi. The kargyraa voice is a very low pitched voice that ranges out of the modal register. The kargyraa voice is very basic in Kai and perceptually identical to Tibetan chant.


Fig. 1: Coronal section of human larynx

3. Ventricular folds (or false vocal folds): Another pair of folds than vocal folds in human larynx

The ventricular folds or false vocal folds (VTFs) are a pair of soft and flaccid folds which exist above the vocal folds (Fig. 1). While the vocal folds (VFs) have a mechanism that change the stiffness, thickness, and longitude by the muscles (mainly by the action of thyroarytenoid muscle), the VTFs are incapable of becoming tense, since they contain very few muscle fibres. It seems that the VTFs are capable of moving with the arytenoid cartilages. They are also abducted and adducted by the action of certain laryngeal muscles. The VTFs as well as the VFs act as air traps from lungs and prevent foreign substances from entering the lower respiratory tract. In normal phonation, the VTFs do not vibrate. But among some patients with dysphonia, the vibration of the VTFs is sometimes observed. 

Fig. 2: High speed digital imaging system

4. Vocal fold and ventricular fold vibrations

We observed laryngeal movements in throat singing directly and indirectly by simultaneous recording of high-speed digital images, and EGG (Electroglottography) and sound waveforms (Fig. 2). The high-speed digital images were captured at 4500 frames/s through a flexible endoscope inserted into the nose cavity of a singer. 

We obtained the following results from our observation. The common features of the squeezed and kargyraa voices which are an overall constriction of the supra-structures of the glottis and vibration of the VTFs. The difference lies in the narrowness of the constriction and the manner of VTF vibration. In the squeezed voice, the VTFs vibrate at the same frequency as the VFs and both vibrate in the opposite phase (Fig. 3). In the kargyraa voice, the VTFs can be assumed to close once for every two periods of closure of the VFs, and contribute to the generation of the subharmonic tone of kargyraa (Fig. 4).

Fig. 3: High-speed images of the laryngeal movement for squeezed voice
Fig. 4: High-speed images of the laryngeal movement for kargyraa voice


5. What is a beautiful singing voice?

Throat singers are able to keep healthy, clear, and beautiful voices though they use pressed-type voices which are regarded to be a non-preferable phonation in European traditional musical pedagogy. They are able to use VTFs as well as VFs and produce their preferable voices without hurting their phonatory organs. Moreover, anyone can become skilled at producing these laryngeal voices. 

Thus, the phonation of throat singing is natural and not mysterious.



We would like to thank Kiyoshi Honda, Koichi Makigami, Caroline Menezes, Johan Sundberg, and Masahiko Todoriki for their helpful discussions.


  1. S.Adachi and M.Yamada, An acoustical study of sound production in biphonic singing, Xöömij. J. Acoust. Soc. Am., 105, pp.2920–2932, 1999.
  2. T.C.Levin and M.E.Edgerton, The throat singers in tuva. Scientific American , Sep-1999, pp.80–87, 1999.
  3. L.Fuks, B.Hammarberg, and J.Sundberg, A self-sustained vocal-ventricular phonation mode: acoustical, aerodynamic and glottographic evidences. KTH TMH-QPSR, 3/1998, pp.49–59, 1998.
  4. H.Imagawa, K.-I.Sakakibara, T.Konishi, and S.Niimi, Throat singing synthesis by a laryngeal voice model based on vocal fold and false vocal fold vibrations. Proc. of Study Group on Musical Info., 01-MUS-39, pp. 71–78, Info. Processing Soc. Jpn., in Japanese, 2001.
  5. P.-Å. Lindestat, M.Sodersten, B.Merker, and S.Granqvist, Voice source characteristics in mongolican “throat singing” studied with high-speed imaging technique, acoutic spectra, and inverse filtering. J. Voice, 15, pp. 78–85, 2001.
  6. K.-I.Sakakibara, S.Adachi, T.Konishi, K.Kondo, E.Z.Murano, M.Kumada, M.Todoriki, H.Imagawa, and S. Niimi, Analysis of vocal fold vibrations in throat singing. Tech Rep. Musical Acoust. of Acoust. Soc. Jpn., 19-4, pp. 41–48, in Japanese, 2000.
  7. 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 khoomei. Proc. of ICMC, pp. 135– 138, 2001.
  8. K.-I.Sakakibara, H.Imagawa, S.Niimi, and N.Osaka, Synthesis of the laryngeal source of throat singing using a 2×2-mass model.Proc. of ICMC, pp. 5 — 8, 2002.




Nathalie Henrich, John Smith and Joe Wolfe: Harmonic singing (or overtone singing) vs normal singing


Harmonic singing (or overtone singing) vs normal singing

Harmonic singing shares techniques with diphonic singing, overtone singing, xoomi singing, sygyt singing, throat singing, Tuva singing etc. We explain some of the acoustics of this style of singing in terms of the measured acoustical response of the vocal tract. In this technique, the singer emphasises one high harmonic of the voice to such an extent that it is heard separately from the low pitched note being sung. Different notes in the harmonic series may be chosen by changing the frequency of the resonance in the vocal tract that gives rise to it.

For background information on speech and ordinary singing, see our Introduction to the acoustics of the vocal tract. For background about our research and techniques, see this link. On this page, we begin by looking at how the vocal tract behaves for a whisper, where the resonances of the tract are most clear, then for normal singing, then for harmonic singing. But first, some sound examples:


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In the first, Jer Ming Chen (a postdoctoral researcher in this lab) sings his own tune, called Desert Lullaby. In the second, he sings up a harmonic series, starting at the fourth harmonic. No treatment of the recording. How does he do that? We’ll need to start with some background first.

Whisper. In the first figure, a subject whispers the vowel in ‘hoard’. We show the frequency response of the vocal tract (For an explanation of the measurements, follow this link.) The sound of the whisper itself is masked by the injected signal used to measure the vocal tract resonances. The figure shows several peaks, indicated by the arrows. At these frequencies, the sound produced at the vocal folds is most effectively transmitted as sound produced in the external air. (Technically, these are peaks in the acoustic impedance of the vocal tract. At these resonant frequencies, the tract operates most effectively as an impedance transformer between the relatively high acoustic impedance of the tract and the low impedance of the radiation field at the mouth.)


graph showing the frequency response of the vocal tract for a whisper

Normal singing. In the figure below, the subject sings the same vowel at the pitch Bb3 (117 Hz). In this graph, you can see the harmonics of the voice, and you can see that the fourth and sixth harmonics appear stronger in the sound spectrum because they are near resonances of the tract.


graph showing the frequency response of the vocal tract for a sung vowel OR

Over the range shown and for this vowel, this subject’s vocal tract has six resonances, which are indicated by the arrows. Note that the subject changes the first two resonances a little between whispering and singing. The frequencies of these two resonances determine the vowel in a particular accent. It is not unusual for people to have different accents when whispering, speaking and singing. The higher resonances are also substantially changed, probably because rather different vocal mechanisms are used in whispering and singing.

Harmonic singing. The next graphs show two examples of harmonic singing. In this technique, one of the vocal tract resonances is made much stronger, while all the others are weakened. The strong resonance can be made so strong that it selects one of the harmonics and makes it so much stronger than its neighbours that we can hear it as a separate note. Hear it is the eighth harmonic that is amplified. Although the fundamental is only 8 dB lower than the selected harmonic, the fundamental lies in a range in which our ears are much less sensitive, so it sounds much less loud.


graph showing the frequency response of the vocal tract for harmonic singing

How do you do it? With some difficulty! One way to strengthen the second resonance, at the expense of the others, is to make a small mouth opening and also a relatively tight constriction between the tongue and the roof of the mouth. But mainly it takes a lot of practice, using feedback. Usually the feedback comes from finding a reasonably reverberant environment (bathroom, stairwell) and listening for the individual harmonics. (Another type of feedback is to use a of the spectrum, using your computer’s sound card. Yet another display uses the graphs shown here, but this last is not readily available.)

In traditional practice, some singers hold the sung pitch (fundamental) constant, and then tune the vocal tract resonances to choose one or another harmonic. They can therefore play the ‘instrument’ using the natural harmonics, just like players of the natural trumpet or horn. Skilled practitioners can vary the voice pitch and the resonant frequency independently. In the next graph, the fundamental has been lowered and the resonance has been raised, with the result that it is the twelfth harmonic that is amplified.


graph showing the frequency response of the vocal tract for armonic singing

For some harmonic singers, more complicated effects than those described here may be involved. It has been suggested that, for some sygyt singers, the strong resonance in the vocal tract may drive an oscillation in the false vocal folds. This could produce a stronger signal at the high pitch. Further, because the false vocal folds would be nonlinear oscillators, they would produce strong components at integral multiples of the high pitch frequency, ie at n*f0, 2n*f0, 3n*f0 etc. An example of such a spectrum and an explanation of the false vocal fold mechanism is given by Chen-Gia Tsai at this link.

This research is part of a project investigation the acoustics of singing in general. It is undertaken by Nathalie HenrichJohn Smith and Joe Wolfe.



Some related pages and explanatory notes

Some explanatory notes


Orpheo’s Angel – Overtone Singing – Jan Heinke, GERMANY


Uploaded on Jan 6, 2009
Spectrogram of german overtone singer Jan Heinke http://www.stahlquartett.de singing his own composition “Orpheo’s Angel”.
Spectrogram created with Overtone Analyzer http://www.sygyt.com

Normalized Spectrum for easy comparison of relative harmonic intensity in Overtone Analyzer


Published on Apr 11, 2013
This video shows how to compare the relative intensity of the harmonics in a recording with the new normalized spectral display in Overtone Analyzer. Instead of showing the absolute intensity in the spectrum, each point in time is scaled so that the loudest harmonic at that point has zero decibel, and the intensity of all other harmonics is relative to the loudest one. This makes it easier to visualize the spectral composition and the timbre of the sound.

The overtone singing is done by Wolfgang Saus (http://www.oberton.org), and the software is Overtone Analyzer (http://www.sygyt.com).