Estimation Of Vocal Tract Shape Research Articles

Dual estimation based vocal tract shape computation

This paper presents a new method for direct estimation of vocal tract shape from the speech signal. The method computes cross-sectional areas of uniform-length cylindrical tubes comprising the vocal tract. Cross-sectional areas are calculated from reflection coefficients at tube junctions whose values depend on the areas of adjoining tubes. A new state space representation of the speech production system has been formulated in which reflection coefficients are parameters. The state space model has been constructed using state equations of the glottal flow signal and vocal tract formulated from Liljencrants–Fant model and concatenated tube model respectively. Dual extended Kalman filtering algorithm has been used for estimation of unknown parameters of the system. The estimated reflection coefficients are then used to compute cross-sectional areas of the vocal tract. The performance of proposed technique has been compared to an existing shape estimation method proposed by Wakita. For both synthesized and natural speech signals, the performance of proposed method has been found to be comparable to the existing one. Nevertheless, the Kalman filter algorithm used in proposed method has provisions to tune measurement noise covariance which can be adjusted based on the noise level in speech. Therefore, the performance of proposed method has been seen to be comparatively more robust to noise than the existing technique.

Analysis of Vocal Tract Shape Variability based on Formant Frequency Ratio at Various Conditions of Vowels for Indian English Speakers

The paper presents the notability of variation of vocal tract shape and formant frequency with its adjacent ratios, for the Indian English speakers for the five vowels of the English language. we have estimated the vocal tract shape of the Indian English speakers. For the estimation we have incorporated Autoregressive Model and the same for the formant frequency. The speech samples are considered with three various utterances namely the consumption of Ice cold water, with time relaxation of five minutes compared with normal recordings of the vowels namely /a/, /e/, /I/, /o/ and /u/. These utterances are recorded for 20 individual iterations. the vocal tract shape estimation and formant frequency estimation are done on the Matlab platform. the vocal tract shape of first vowel /a/ comes to normal shape rapidly with time lapse of five minutes. the vocal tract shape of vowel /e/ shrinks after consumption of ice cold water and slowly attains the normal shape. The vowel /I/ and /or/ vocal tract shape changes linearly for all the conditions considered, whereas the vocal tract shape of /u/ compresses for ice cold water and retains to be same even after a time lapse of five minutes. All the above variations are done by considering the vocal tract length of 17cm and it is modelled according to lossless uniform tube model. these outcomes are used for observation of vocal tract infection among the speech disorder patients, it can be adopted for the user authentication system by considering it as a vocal tract signature.

Study of Vocal Tract Shape Estimation Techniques for Children

Accurate depiction of the vocal tract shape is essential for development of speech training aids for hearing impaired. Speech therapists have concluded from their research that if speech disorders are detected at an early stage then the rectification of those becomes faster and to a great accuracy. In case of adults, the vocal tract shape estimation can be performed by using techniques like X-Ray, MRI or using articulatory analysis by synthesis. Due to certain difficulties present in the methods mentioned like radiation effect and loud sound impulses produced by rapid switching of magnetic field are not considered suitable for children. Thus there is lack of availability of vocal tract shape data for children due to inability to use direct estimation methods for children. So it becomes necessary to carry out comparative study of vocal tract shape estimation techniques of children using indirect vocal tract shape estimation techniques. This paper aims to make available a considerable amount of data to researchers for study towards children's vocal tract shape using implemented techniques.The final objective of research work is to perform a detailed study on techniques available for vocal tract shape estimation, to implement and further compare the covariance and lattice methods for children using MATLAB software. Currently, the vocal tract shape estimation based on autocorrelation method is implemented and the results obtained are presented.

Validation of Optimum Algorithm Parameters Required to Estimate Vocal Tract Shape for Children Using LPC Analysis

Severe or profound deafness in hearing impaired children, can curb their ability to speak due to the lack of auditory feedback. There has been a considerable attempt in developing commercial speech training aids for such children which give feedback of acoustic and articulatory parameters. Speech training aids based on visual feedback of vocal tract shape (VTS) are reported to be useful for the improvement in speech production. Since realistic VTS estimation for adult speakers and their validation has already been done successfully, VTS estimation is now necessarily required in case of children too, so that they get trained in speech at an early age. The investigation on vocal tract shape estimation based on LPC analysis of speech by appropriately selecting some of the algorithm parameters such as vocal tract length, LPC order, and speech sampling rate has been done in our previous work. This paper attempts to validate the obtained results for vocal tract shapes corresponding to certain recorded vowels from children belonging to specific age groups. Since MRI images of VTS are unavailable for articulating children, validation of our results is based on the results from researchers who have used other indirect techniques to obtain VTS.

Acoustic vocal tract model of one-year-old children

The physical shape of vocal tract and its formant (resonant) frequencies are directly related. The study of this functional connectivity is essential in speech therapy practice with children. Most of the perceived children's speech anomalies can be explained on a physical level: malfunctioning movement of articulation organs. The current problem is that there is no enough data on the anatomical shape of children's vocal tract to create its acoustic model. Classical techniques for vocal tract shape imaging (X-ray, magnetic resonance, etc.) are not appropriate for children. One possibility is to start from the shape of the adult vocal tract and correct it based on anatomical, morphological and articulatory differences between children and adults. This paper presents a method for vocal tract shape estimation of the child aged one year. The initial shapes of the vocal tract refer to the Russian vowels spoken by an adult male. All the relevant anatomical and articulation parameters, that influence the formant frequencies, are analyzed. Finally, the hypothetical configurations of the children's vocal tract, for the five vowels, are presented.

Estimation of Place of Articulation During Stop Closures of Vowel–Consonant–Vowel Utterances

Production of vowel-oral stop consonant-vowel utterances involves movement of articulators from the articulatory position of the initial vowel towards that of the oral stop closure, and then to that of the final vowel. As the closure segments have zero or low signal energy, linear predictive coding (LPC)-based estimation of vocal tract shape fails during stop closure. This paper reports a technique for estimation of place of articulation during stop closures by performing bivariate polynomial modeling on vocal tract area values during transition segments preceding and following the closure. The technique with second-degree polynomial modeling was found to be suitable for estimating the place of maximum constriction during stop closure segments of vowel-consonant-vowel utterances with bilabial, alveolar, and velar stops. The estimated places compared well with the actual constriction locations observed from the articulatory data. The technique may be useful for improving effectiveness of speech-training aids for production of stop consonants by providing visual feedback of the estimated place of articulation.

Vocal tract shape estimation using three noninvasive transducers

Sentence-level speech simulation requires a description of vocal tract shape parameters as a function of time. Vowel-like configurations can often be derived from a microphone signal; however, the influence of consonants may be more easily detected with the use of additional signals. The electroglottograph (EGG) and an articulatory transducer [McGarr and Lofqvist, J. Acoust. Soc. Am. 72, 34–42 (1982)] are employed to increase the accuracy of vocal tract shape estimation. The microphone signal is analyzed on a frame-by-frame basis for spectral features, energy, and zero-crossing rate. The EGG provides information regarding voicing onset and offset, and the articulatory signal is used to indicate closure and lip rounding. These data are combined to select an appropriate area function for each frame of the sentence. The resulting temporal map of area functions is interpolated and sent to a wave reflection simulator to reconstruct the speech. [Work supported by NIH Grant No. DCO2532.]

The geometric vocal tract variables controlled for vowel production: proposals for constraining acoustic-to-articulatory inversion

Studies on vocal tract shape estimation from the speech signal have thoroughly established that no unique inversion from the acoustic speech signal to the vocal tract area function is possible. However, by emphasizing the non-uniqueness of vocal tract shapes, these studies have exaggerated the possibilities of compensatory articulation, which in turn challenges the traditional classification in terms of place of articulation. We suggest, in the light of more recent studies, that this phonetic concept was too hastily discarded. These studies show that certain geometric variables are very important in the process of motor control and in the typology and description of vowel systems. The aim of this paper is to show the possibility and the value of deriving these controlled variables, rather than the entire vocal tract geometry, from acoustic parameters. For this purpose, using a statistical model of the vocal tract integrating articulatory constraints, we generated a 60 000 item look-up table of vocalic configurations. The analysis of 10 French vowels shows that, for the majority of them, it is possible to associate the formant patterns with the well known geometric parameters, namely the lip area and the location and dimension of the tongue constriction. This result seems to confirm that some geometric variables controlled during production can be inferred from the acoustic signal if articulatory constraints are taken into account in the inversion procedure.