Papers - KITAMURA Tatsuya
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MRI-Based Study on Morphological and Acoustic Properties of Mandarin Sustained Vowels
WANG Gaowu, KITAMURA Tatsuya, LU Xugang, DANG Jianwu, KONG Jiangping
J Signal Process 12 ( 4 ) 311 - 314 2008.7
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Deformation of the hypopharyngeal cavities due to F0 changes and its acoustic effects Reviewed
Hironori Takemoto, Tatsuya Kitamura, Kiyoshi Honda, Shinobu Masaki
Acoustical Science and Technology 2008.4
Joint Work
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Single-matrix formulation of a time domain acoustic model of the vocal tract with side branches
MOKHTARI Parham, TAKEMOTO Hironori, KITAMURA Tatsuya
Speech Communication 50 ( 3 ) 179 - 190 2008.3
Joint Work
Publisher：ELSEVIER SCIENCE BV
Although it has been found that the piriform fossae play an important role in speech production and acoustics, the popular time domain articulatory synthesizer of [Maeda, S., 1982. A digital simulation method of the vocal-tract system. Speech Comm. 1 (3–4), 199–229] currently cannot include any more than one side branch to the acoustic tube that represents the main vocal tract. To overcome this limitation, in this paper we extended Maeda's (1982) simulation method, by mathematical reformulation in terms of a single-matrix equation having a system matrix that is both sparse and symmetric. Using vocal tract area functions measured by MRI, the simulation results showed that the piriform fossae suppress the energy in the higher frequencies by introducing spectral zeros around 4–5 kHz, and also tend to lower the second formant of vowels. These spectral changes agree with results produced using a well-tested frequency domain transmission-line method, thus validating our new formulation of the time domain synthesizer. The reformulation can be easily extended to accommodate any number of vocal tract side branches, thus enabling more realistic, physiologically correct acoustic simulation of speech production.
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Effects of acoustic modification on perception of speaker characteristics for sustained vowels
Tatsuya Kitamura, Takeshi Saitou
Acoustical Science and Technology 2007.6
Joint Work
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Vocal tract length perturbation and its application to male-female vocal tract shape conversion
Seiji Adachi, Hironori Takemoto, Tatsuya Kitamura, Parham Mokhtari, Kiyoshi Honda
Journal of the Acoustical Society of America 121 ( 6 ) 3874 - 3885 2007.6
Joint Work
Publisher：ACOUSTICAL SOC AMER AMER INST PHYSICS
An alternative and complete derivation of the vocal tract length sensitivity function, which is an equation for finding a change in formant frequency due to perturbation of the vocal tract length [Fant, Quarterly Progress and Status Rep. No. 4, Speech Transmission Laboratory, Kungliga Teknisha H6gskolan, Stockholm, 1975, pp. 1-14] is presented. It is based on the adiabatic invariance of the vocal tract as an acoustic resonator and on the radiation pressure on the wall and at the exit of the vocal tract. An algorithm for tuning the vocal tract shape to match the formant frequencies to target values, such as those of a recorded speech signal, which was proposed in Story [J. Acoust. Soc. Am. 119, 715-718 (2006)], is extended so that the vocal tract length can also be changed. Numerical simulation of this extended algorithm shows that it can successfully convert between the vocal tract shapes of a male and a female for each of five Japanese vowels. (c) 2007 Acoustical Society of America.
DOI： 10.1121/1.2730743
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Principal components of vocal tract area functions and inversion of speech by linear regression of cepstrum coefficient
Parham Mokhtari, Hironori Takemoto, Tatsuya Kitamura, Kiyoshi Honda
Journal of Phonetics 2007.1
Joint Work
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A bone-conduction system for auditory stimulation in MRI Reviewed
Yukiko Nota, Tatsuya Kitamura, Hironori Takemoto, Hiroyuki Hirata, Kiyoshi Honda, Yasuhiro Shimada, Ichiro Fujimoto, Yuko Syakudo, Shinobu Masaki
Acoustical Science and Technology 2007.1
Joint Work
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Principal components of vocal-tract area functions and inversion of vowels by linear regression of cepstrum coefficients
Parham Mokhtari, Tatsuya Kitamura, Hironori Takemoto, Kiyoshi Honda
JOURNAL OF PHONETICS 35 ( 1 ) 20 - 39 2007.1
Joint Work
Publisher：ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD
This paper addresses the following two hypotheses: (1) vocal-tract area functions of Japanese vowels can be accurately represented by a linear combination of only a few principal components which, furthermore, are similar to those reported in the literature for different languages; and (ii) the principal components' weights can be predicted and area functions thereby accurately estimated from acoustics by linear regression of cepstrum parameters. To test these hypotheses, synchronized acoustic and vocal-tract 3D MRI data were recorded from an adult male Japanese speaker for both sustained and dynamic vowel utterances. The first two principal components explained covariations in vocal-tract shape and length accounting for 94-97% of the total variance, and indeed provided a cross-linguistic validation of the two underlying components of vowel production emergent from the literature. Multiple linear regression models were then evaluated for their accuracy in reconstructing the area functions of the dynamic utterance by predicting the first two PC coefficients, using either carefully measured formants or cepstral coefficients defined in various frequency bands. The best formant-based regression model required all four formants, with a mean adjusted correlation of 0.93 and mean absolute errors of 0.187 cm(2) in area and 0.131 em in vocal-tract length. The best cepstrum-based regression model prescribed 24 cepstral coefficients defined in the frequency band 0-4 kHz, with a mean adjusted correlation of 0.92 and mean absolute errors of 0.102 cm(2) in area and 0.082 cm in vocal-tract length. These results suggest that vowel production features, properly constrained by PCA modeling, can be mapped with sufficient accuracy from easily measured cepstrum parameters. More work is required to reduce the dependence on MRI data, to extend the applicability of these methods to different voice qualities and different speakers, and to select a smaller subset of acoustic parameters for more robust, real-time inversion. (c) 2006 Elsevier Ltd. All rights reserved.
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An MRI-based time-domain speech synthesis system Reviewed
Tatsuya Kitamura, Hironori Takemoto, Parham Mokhtari, Toshio Hirai
Journal of the Acoustical Society of America 120 ( 5 ) 3037 2006.12
Joint Work
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Changes in vocal tract resonance during a pitch cycle Reviewed
Tatsuya Kitamura, Seiji Adachi
Journal of the Acoustical Society of America 120 ( 5 ) 3351 2006.12
Joint Work
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Measurements of MRI scanning noise by an optical microphone
Kitamura Tatsuya, Masaki Shinobu, Shimada Yasuhiro, Fujimoto Ichiro, Syakudo Yuko, Honda Kiyoshi
The Journal of the Acoustical Society of Japan 62 ( 5 ) 379 - 382 2006.5
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Investigation of effectiveness to estimate vocal tract transfer functions by FEM
Nishimoto Hironori, Akagi Masato, Kitamura Tatsuya, Suzuki Noriko
The Journal of the Acoustical Society of Japan 62 ( 4 ) 306 - 315 2006.4
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Acoustic roles of the laryngeal cavity in vocal tract resonance Reviewed
Hironori Takemoto, Seiji Adachi, Tatsuya Kitamura, Parham Mokhtari, Kiyoshi Honda
Journal of the Acoustical Society of America 2006.4
Joint Work
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Cyclicity of laryngeal cavity resonance due to vocal fold vibration Reviewed
Tatsuya Kitamura, Hironori Takemoto, Seiji Adachi, Parham Mokhtari, Kiyoshi Honda
Journal of the Acoustical Society of America 120 ( 4 ) 2239 - 2249 2006.4
Joint Work
Publisher：ACOUSTICAL SOC AMER AMER INST PHYSICS
Acoustic effects of the time-varying glottal area due to vocal fold vibration on the laryngeal cavity resonance were investigated based on vocal tract area functions and acoustic analysis. The laryngeal cavity consists of the vestibular and ventricular parts of the larynx, and gives rise to a regional acoustic resonance within the vocal tract, with this resonance imparting an extra formant to the vocal tract resonance pattern. Vocal tract transfer functions of the five Japanese vowels uttered by three male subjects were calculated under open- and closed-glottis conditions. The results revealed that the resonance appears at the frequency region from 3.0 to 3.7kHz when the glottis is closed and disappears when it is open. Real spectra estimated from open- and closed-glottis periods of vowel sounds also showed the on-off pattern of the resonance within a pitch period. Furthermore, a time-domain acoustic analysis of vowels indicated that the resonance component could be observed as a pitch-synchronized rise-and-fall pattern of the bandpass amplitude. The cyclic nature of the resonance can be explained as the laryngeal cavity acting as a closed tube that generates the resonance during a closed-glottis period, but damps the resonance off during an open-glottis period.
DOI： 10.1121/1.2335428
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Difference in vocal tract shape between upright and supine postures: Observations by an open-type MRI scanner
KITAMURA Tatsuya, TAKEMOTO Hironori, HONDA Kiyoshi, SHIMADA Yasuhiro, FUJIMOTO Ichiro, SYAKUDO Yuko, MASAKI Shinobu, KURODA Kagayaki, OKU-UCHI Noboru, SENDA Michio
Acoustical Science and Technology 26 ( 5 ) 465 - 468 2005.9
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Individual variation of the hypopharyngeal cavities and its acoustic effects
Tatsuya Kitamura, Kiyoshi Honda, Hironori Takemoto
Acoustical Science and Technology 26 ( 1 ) 16 - 26 2005.1
Joint Work
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A method of tooth superimposition on MRI data for accurate measurement of vocal tract shape and dimensions Reviewed
Hironori Takemoto, Tatsuya Kitamura, Hironori Nishimoto, Kiyoshi Honda
Acoustical Science and Technology 25 ( 6 ) 468 - 474 2004.11
Joint Work
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Exploring human speech production mechanisms by MRI
Kiyoshi Honda, Hironori Takemoto, Tatsuya Kitamura, Satoru Fujita, Sayoko Takano
IEICE Transactions on Information and Systems E87-D ( 5 ) 1050 - 1058 2004.5
Joint Work
Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG
Recent investigations using magnetic resonance imaging (MRI) of human speech organs have opened up new avenues of research. Visualization of the speech production system provides abundant information on the physiological and acoustic realization of human speech. This article summarizes the current status of MRI applications with respect to speech research as well as our own experience of discovery and re-evaluation of acoustic events emanating from the vocal tract and physiological mechanisms.
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Development of a Japanese reading resource bank using the Internet
Yoshiko Kawamura, Tatsuya Kitamura
6 241 - 255 2001
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Yoshiko Kawamura, Tatsuya Kitamura, Rei Hobara
24 7 - 12 2000.8