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Objective Stroke survivors commonly suffer from dysphagia, originating from oro-facial impairments which affect swallowing function. Functional therapy often employs tongue exercises that require the patient to perform short motion sequences. Evaluating the patients performance on those exercises is difficult, because there is no reliable form of visual feedback. Methods We propose an optopalatographic device that does not require a personalized dental retainer and is capable of measuring tongue movement trajectories intraorally. The device features nine optical proximity sensors at 100 Hz and is fixated against the hard palate with a specifically developed palatal adhesive. The sensing capabilities of the device were evaluated on a tongue gesture corpus recorded from nine healthy individuals, containing eight different tongue exercises commonly used in functional dysphagia therapy. Results The measured tongue trajectories contained temporally and spatially resolved information about the tongue movement and location during each exercise. Furthermore, a simple DTW-kNN classifier was able to distinguish the exercises from one another with an average classification accuracy of 97.9 % and 61.4 % (cross-validation and inter-speaker test accuracy, respectively). Conclusion the device can provide real-time feedback for tongue motion and we obtained promising gesture recognition results with relatively few sensors, even in the absence of a personalized dental retainer. Significance Non-personalized optopalatography is readily available and could aid in improving functional dysphagia therapy by providing visual feedback to both the physician and patient.

The influence of non-smooth trachea walls on phonation onset and offset pressures and the fundamental frequency of oscillation were experimentally investigated for three different synthetic vocal fold models. Three models of the trachea were compared: a cylindrical tube (smooth walls) and wavy-walled tubes with ripple depths of 1 and 2 mm. Threshold pressures for the onset and offset of phonation were measured at the lower and upper ends of each trachea tube. All measurements were performed both with and without a supraglottal resonator. While the fundamental frequency was not affected by non-smooth trachea walls, the phonation onset and offset pressures measured right below the glottis decreased with an increasing ripple depth of the trachea walls (up to 20% for 2 mm ripples). This effect was independent from the type of glottis model and the presence of a supraglottal resonator. The pressures at the lower end of the trachea and the average volume velocities showed a tendency to decrease with an increasing ripple depth of the trachea walls but to a much smaller extent. These results indicate that the subglottal geometry and the flow conditions in the trachea can substantially affect the oscillation of synthetic vocal folds.

The estimation of formant frequencies from acoustic speech signals is mostly based on Linear Predictive Coding (LPC) algorithms. Since LPC is based on the source-filter model of speech production, the formant frequencies obtained are often implicitly regarded as those for an infinite glottal impedance, i.e., a closed glottis. However, previous studies have indicated that LPC-based formant estimates of vowels generated with a realistically varying glottal area may substantially differ from the resonances of the vocal tract with a closed glottis. In the present study, the deviation between closed-glottis resonances and LPC-estimated formants during phonation with different peak glottal areas has been systematically examined both using physical vocal tract models excited with a self-oscillating rubber model of the vocal folds, and by computer simulations of interacting source and filter models. Ten vocal tract resonators representing different vowels have been analyzed. The results showed that F1 increased with the peak area of the time-varying glottis, while F2 and F3 were not systematically affected. The effect of the peak glottal area on F1 was strongest for close-mid to close vowels, and more moderate for mid to open vowels.

Self-oscillating bar-mass models of the vocal folds are frequently used as the voice source in articulatory speech synthesis. For these models, a number of ways to handle the entrance loss and the flow separation in the glottis have been proposed. However, the effect of different modeling choices on vocal fold oscillation and glottal flow, and on the quality of synthesized speech has been rarely examined. In this study, a modified two-mass model of the vocal folds was used to simulate phonation for 12 modeling options: three ways to model the entrance loss combined with four ways to model flow separation. For each condition, the following characteristics of the glottal oscillation and flow were determined: the phonation threshold pressure, the frequency range of self-sustained oscillation, the oscillation amplitude for different glottal rest openings, the spectral slope of the flow derivative, the maximum flow declination rate (MFDR), the open quotient (OQ), and the difference between the levels of the first and second harmonics of the flow derivative (H1-H2). In addition, the effect of the modeling options on the perceived naturalness of the synthetic voice was evaluated. There was no effect of the different ways to model entrance loss and flow separation on the phonation threshold pressure and on frequency range, and only a minor effect on MFDR, OQ, and H1-H2. However, there was a strong effect of the flow separation model on the oscillation amplitude, the spectral slope, and on the naturalness of the voice. The voice was perceived as most natural when the flow was assumed to always separate at the minimum glottal diameter.

This study investigated the intrinsic velocities of raising and lowering movements of the velum that are related to its biomechanical structure and aerodynamic conditions. To this end, five subjects produced cyclic transitions between nasals and fricatives as in /s-n-s-n-s-.../ with flat intonation and at two specific speaking rates to minimize contextual and prosodic effects. The velar movements were inferred from the movements of the lateral pharyngeal wall in ultrasound image sequences, which are strongly correlated. The results indicate that velum raising was significantly faster than velum lowering for the two male subjects (24%–49% faster, depending on the subject and speaking rate), but not for the three female subjects. Possible biomechanical and aerodynamic reasons for the observed velocity differences are discussed. The results can inform the interpretation of kinematic data of velar movements with regard to underlying neural control, and improve movement models for articulatory speech synthesis.

Purpose Psychoacoustical studies on transmission characteristics related to bone-conducted (BC) speech, perceived by speakers during vocalization, are important for further understanding the relationship between speech production and perception, especially auditory feedback. For exploring how the outer ear part contributes to BC speech transmission, this article aims to measure the transmission characteristics of bone conduction focusing on the vibration of the regio temporalis (RT) and sound radiation in the ear canal (EC) due to the excitation in the oral cavity (OC). Method While an excitation signal was presented through a loudspeaker located in the enclosed cavity below the hard palate, transmitted signals were measured on the RT and in the EC. The transfer functions of the RT vibration and EC sound pressure relative to OC sound pressure were determined from the measured signals using the sweep-sine method. Results Our findings obtained from the measurements of five participants are as follows: (a) the transfer function of the RT vibration relative to the OC sound pressure attenuated the frequency components above 1 kHz and (b) the transfer function of the EC relative to the OC sound pressure emphasized the frequency components between 2 and 3 kHz. Conclusions The vibration of the soft tissue or the skull bone has an effect of low-pass filtering, whereas the sound radiation in the EC has an effect of 2–3 kHz bandpass filtering. Considering the perceptual effect of low-pass filtering in BC speech, our findings suggest that the transmission to the outer ear may not be a dominant contributor to BC speech perception during vocalization.

Purpose Recently, efforts have been made to investigate the vocal tract using magnetic resonance imaging (MRI). Due to technical limitations, teeth were omitted in many previous studies on vocal tract acoustics. However, the knowledge of how teeth influence vocal tract acoustics might be important in order to estimate the necessity of implementing teeth in vocal tract models. The aim of this study was therefore to estimate the effect of teeth on vocal tract acoustics. Method The acoustic properties of 18 solid (3-dimensional printed) vocal tract models without teeth were compared to the same 18 models including teeth in terms of resonance frequencies ( f Rn ). The f Rn were obtained from the transfer functions of these models excited by white noise at the glottis level. The models were derived from MRI data of 2 trained singers performing 3 different vowel conditions (/i/, /a/, and /u/) in speech and low-pitched and high-pitched singing. Results Depending on the oral configuration, models exhibiting side cavities or side branches were characterized by major changes in the transfer function when teeth were implemented via the introduction of pole-zero pairs. Conclusions To avoid errors in modeling, teeth should be included in 3-dimensional vocal tract models for acoustic evaluation. Supplemental Material https://doi.org/10.23641/asha.5386771

Optopalatography (OPG) is an optical technique to measure the distance between the hard palate and the tongue surface inside the mouth during articulation. The conventional way to measure this distance is only accurate for the special case that the tongue surface is oriented perpendicular to the optical axes of the optical sensors. It introduces an error in the much more common case that the tongue is angled with respect to the sensor axes. In this paper, we present a technique to compensate that error by using a newly devised complete model of light propagation for arbitrary source-reflector-detector setups that considers the complex reflective properties of the tongue surface due to sub-surface scattering. Optimal parameters for our model are found by fitting it to a data set of real-world measurements. For any given arrangement of sensors, simulations of this model can be used to obtain optimal coefficients for a distance error correction term. This term reduces the mean distance error of in vivo data recorded with our electrooptical stomatography (EOS, a multi-modal technique that includes OPG) hardware prototype from 7.38% to 2.25% and the standard deviation from 2.79% to 1.9%. The results are used to significantly improve the precision and accuracy of the distance measurements in real-time EOS recordings and example tongue contours of five German vowels are presented.

Beacause transmission characteristics of bone-conducted (BC) speech from the larynx to auditory systems have not yet been clarified, this paper investigates the transmission characteristics related to the BC speech perception focusing on temporal bone (TB) vibration signals and ear canal (EC) radiated speech signals. First, long-term average spectra (LTAS) of the normally produced speech signals recorded at the lips, TB and EC were analyzed. It was found that the frequency components above 2 kHz were relatively decreased in the TB vibration and those below 1 kHz and above 3 kHz were relatively decreased in the EC-radiated speech. Second, transfer functions from the larynx to the observation positions (the lip, TB, and EC) were measured using transcutaneous excitation at the larynx. It was found that the larynx-to-TB transfer functions partially emphasized the frequency region below 1 kHz and the larynx-to-EC transfer functions attenuated the frequency components below 1 kHz and above 3 kHz. These results indicate that the lower frequency components of BC speech are transmitted through TB vibration and the higher frequency components are transmitted through EC-radiated speech.

Acoustic and articulatory differences between spoken and shouted vowels were analyzed for two male and two female subjects by means of acoustic recordings and midsagittal magnetic resonance images of the vocal tract. In accordance with previous acoustic findings, the fundamental frequencies, intensities, and formant frequencies were all generally higher for shouted than for spoken vowels. The harmonics-to-noise ratios and H1-H2 measures were generally lower for shouted vowels than for spoken vowels. With regard to articulation, all subjects used an increased lip opening, an increased jaw opening, and a lower tongue position for shouted vowels. However, the changes of vertical larynx position, uvula elevation, and jaw protrusion between spoken and shouted vowels were inconsistent among subjects. Based on the analysis results, a perception experiment was conducted to examine how changes of fundamental frequency, subglottal pressure, vocal tract shape, and phonation type contribute to the perception of stimuli created by articulatory synthesis as being shouted. Here, fundamental frequency had the greatest effect, followed by vocal tract shape and lung pressure, with no measurable effect of phonation type.

Fricative voicing distinction was tested for European Portuguese.Stimuli were generated with articulatory synthesis.Voicing maintenance is main perceptual cue, but other acoustic cues strongly interact. This study examined the conditions under which European Portuguese (EP) intervocalic fricatives are perceived as voiced/voiceless with respect to varying voiced-to-devoiced fricative portions, durations, pharyngeal widths and glottal heights. Articulatory speech synthesis incorporating a sophisticated noise source model was used to produce /aCa/ sequences (C=/f v s z ? ?/) for two perception experiments (forced choice voiced/voiceless decision). This approach has the main advantage that all relevant articulatory settings can be manipulated independently. The proportion of fricative voicing was varied between fully devoiced to fully voiced; phoneme durations were varied corresponding to natural EP speech. Glottal height and pharyngeal width each varied amongst three different states. The results showed strong interaction between the cues phoneme duration and voicing maintenance. A voiced-to-devoiced ratio of only 25% was enough to guarantee robust perception of fricative voicing. Phoneme duration and place of articulation had a significant effect on listener decisions, but only for voiced-to-devoiced ratios of 25-50%. Vowel duration, pharyngeal width and glottis height had no significant effect. The study provides new evidence for cue-trading in fricative perception. Furthermore, new insights into laryngeal vs. supra-laryngeal gestural coordination are gained which may facilitate the development of fricative models.

Tongue shape reconstruction based on safe and convenient measurement techniques is of great interest for speech research and speech therapy. Two potentially useful and related measurement techniques for this purpose are electropalatography (EPG) and optopalatography (OPG). While EPG measures the time-varying contact pattern between the hard palate and the tongue, OPG measures distances between the two. Here, we examined the potential of EPG, OPG, and their combination for predicting the whole tongue contour using a multiple linear regression model. The model was trained and tested with tongue shapes and virtual sensor data obtained from Magnetic Resonance Images of sustained articulations of two speakers. When the model was trained and tested with the same speaker, the error of tongue contour reconstruction was significantly lower for predictions based on OPG data than for predictions based on EPG data. When the model was trained with one speaker and tested with the other, the error pattern was less consistent and the overall error was higher. Hence, especially OPG is well suited for tongue contour prediction, but an adaptation method is needed to transfer the model to a new speaker.

Surface electromyography (sEMG) is a well-established procedure for recording swallowing-related muscle activities. Because the use of a large number of sEMG channels is time consuming and technically sophisticated, the aim of this study was to identify the most significant electrode positions associated with oropharyngeal swallowing activities. Healthy subjects (N = 16) were tested with a total of 42 channels placed in M. masseter, M. orbicularis oris, submental and paralaryngeal regions. Each test subject swallowed 10 ml of water five times. After having identified 16 optimal electrode positions, that is, positions with the strongest signals quantified by the highest integral values, differences to 26 other ones were determined by a Mann-Whitney U test. Kruskal-Wallis H test was utilized for the analysis of differences between single subjects, subject subgroups, and single electrode positions. Factors associated with sEMG signals were examined in a linear regression. Sixteen electrode positions were chosen by a simple ranking of integral values. These positions delivered significantly higher signals than the other 26 positions. Differences between single electrode positions and between test subjects were also significant. Sixteen most significant positions were identified which represent swallowing-related muscle potentials in healthy subjects.

Purpose: To explore possible effects of tongue piercing on perceived speech quality. Methods: Using a quasi-experimental design, we analyzed the effect of tongue piercing on speech in a perception experiment. Samples of spontaneous speech and read speech were recorded from 20 long-term pierced and 20 non-pierced individuals (10 males, 10 females each). The individuals having a tongue piercing were recorded with attached and removed piercing. The audio samples were blindly rated by 26 female and 20 male laypersons and by 5 female speech-language pathologists with regard to perceived speech quality along 5 dimensions: speech clarity, speech rate, prosody, rhythm and fluency. Results: We found no statistically significant differences for any of the speech quality dimensions between the pierced and non-pierced individuals, neither for the read nor for the spontaneous speech. In addition, neither length nor position of piercing had a significant effect on speech quality. The removal of tongue piercings had no effects on speech performance either. Rating differences between laypersons and speech-language pathologists were not dependent on the presence of a tongue piercing. Conclusions: People are able to perfectly adapt their articulation to long-term tongue piercings such that their speech quality is not perceptually affected.

Previous studies related to auditory feedback have found that hearing one's own voice has important roles in maintaining one's speech production. However, it is still unclear how perception of one's bone-conducted (BC) speech affects one's speech production, since most studies have just presented white/pink noise for masking speakers’ BC speech without enough consideration of acoustical and transmission characteristics of BC speech itself. This study aims to investigate spectral characteristics of the observable parts of BC speech (temporal bone (TB) vibration and ear canal (EC) speech) and transmission characteristics related to them. Spectral envelopes of vowel utterances and long-term average spectrum (LTAS) of sentence utterances were analyzed. Moreover, transfer functions from larynxes to TB and EC were measured using transcutaneous vibration signals. As results of these analyses, although the spectral shapes are different among the vowels in TB vibration and EC speech, it was found that the transmission from larynxes to TB emphasizes lower frequency components and the transmission from larynxes to EC emphasizes the higher frequency components. [Work supported by JSPS KAKENHI Grant No. JP. 17J03679, and Grant in Aid for Scientific Research Innovative Areas (Grant No. 16H01669, 18H05004) from MEXT, Japan.] Previous studies related to auditory feedback have found that hearing one's own voice has important roles in maintaining one's speech production. However, it is still unclear how perception of one's bone-conducted (BC) speech affects one's speech production, since most studies have just presented white/pink noise for masking speakers’ BC speech without enough consideration of acoustical and transmission characteristics of BC speech itself. This study aims to investigate spectral characteristics of the observable parts of BC speech (temporal bone (TB) vibration and ear canal (EC) speech) and transmission characteristics related to them. Spectral envelopes of vowel utterances and long-term average spectrum (LTAS) of sentence utterances were analyzed. Moreover, transfer functions from larynxes to TB and EC were measured using transcutaneous vibration signals. As results of these analyses, although the spectral shapes are different among the vowels in TB vibration and EC speech, it was found that the transmis...

We are currently developing a technology called “electrooptical stomatography” to measure and visualize articulatory movements within the vocal tract using electrical contact sensors and optical proximity sensors. To measure tongue movements with the optical sensors in this system, a mapping between the raw sensor values and actual tongue positions has to be determined. This mapping is non-linear and different for every tongue and sensor. The lack of an accurate, reliable calibration method has so far prevented wide-spread use of optical measurements within the vocal tract. Here, we present a calibration method based on a multi-linear regression model that maps the sensor value at a single distance of 0mm to calibration values at 0, 5, 10, 15, 20, 25, and 30mm. The coefficients of the model are determined by a least-squares regression in 25 training data sets (recorded with 5 subjects and 5 sensors). Evaluation in a leave-one-out cross-validation and on five more data sets recorded with another, different subject on 5 additional sensors yields very good results with maximum median position errors close to 1mm. The calibration of the optical sensors can therefore be semi-automatically accomplished based on a single, easily obtainable measurement during direct tongue contact.

Vocal emotions are signaled by specific patterns of prosodic parameters, most notably pitch, phone duration, intensity, and phonation type. Phonation type was so far the least accessible parameter in emotion research, because it was difficult to extract from speech signals and difficult to manipulate in natural or synthetic speech. The present study built on recent advances in articulatory speech synthesis to exclusively control phonation type in re-synthesized German sentences spoken with seven different emotions. The goal was to find out to what extent the sole change of phonation type affects the perception of these emotions. Therefore, portrayed emotional utterances were re-synthesized with their original phonation type, as well as with each purely breathy, modal, and pressed phonation, and then rated by listeners with respect to the perceived emotions. Highly significant effects of phonation type on the recognition rates of the original emotions were found, except for disgust. While fear, anger, and the neutral emotion require specific phonation types for correct perception, sadness, happiness, boredom, and disgust primarily rely on other prosodic parameters. These results can help to improve the expression of emotions in synthesized speech and facilitate the robust automatic recognition of vocal emotions.

Gender dysphoria (also known as “transsexualism”) is characterized as a discrepancy between anatomical sex and gender identity. Research points towards neurobiological influences. Due to the sexually dimorphic characteristics of the human voice, voice gender perception provides a biologically relevant function, e.g. in the context of mating selection. There is evidence for a better recognition of voices of the opposite sex and a differentiation of the sexes in its underlying functional cerebral correlates, namely the prefrontal and middle temporal areas. This fMRI study investigated the neural correlates of voice gender perception in 32 male-to-female gender dysphoric individuals (MtFs) compared to 20 non-gender dysphoric men and 19 non-gender dysphoric women. Participants indicated the sex of 240 voice stimuli modified in semitone steps in the direction to the other gender. Compared to men and women, MtFs showed differences in a neural network including the medial prefrontal gyrus, the insula, and the precuneus when responding to male vs. female voices. With increased voice morphing men recruited more prefrontal areas compared to women and MtFs, while MtFs revealed a pattern more similar to women. On a behavioral and neuronal level, our results support the feeling of MtFs reporting they cannot identify with their assigned sex.

Voice, as a secondary sexual characteristic, is known to affect the perceived attractiveness of human individuals. But the underlying mechanism of vocal attractiveness has remained unclear. Here, we presented human listeners with acoustically altered natural sentences and fully synthetic sentences with systematically manipulated pitch, formants and voice quality based on a principle of body size projection reported for animal calls and emotional human vocal expressions. The results show that male listeners preferred a female voice that signals a small body size, with relatively high pitch, wide formant dispersion and breathy voice, while female listeners preferred a male voice that signals a large body size with low pitch and narrow formant dispersion. Interestingly, however, male vocal attractiveness was also enhanced by breathiness, which presumably softened the aggressiveness associated with a large body size. These results, together with the additional finding that the same vocal dimensions also affect emotion judgment, indicate that humans still employ a vocal interaction strategy used in animal calls despite the development of complex language. © 2013 Xu et al., published_or_final_version

This paper describes the development of a device that combines the electropalatographic measurement of tongue-palate contact with optical distance sensing to measure the mid-sagittal contour of the tongue and the position of the lips. The device consists of a thin acrylic pseudopalate that contains both contact sensors and optical reflective sensors. Application areas are, for example, experimental phonetics, speech therapy, and silent speech interfaces. With regard to the latter, the prototype of the system was applied to the recognition of vowels from the sensor signals. It was shown that a classifier using the combined input data from both the contact sensors and the optical sensors had a higher recognition rate than classifiers based on only one type of sensory input.

We present a novel 3D vocal tract model and a method to control the articulatory movements of the model. The vocal tract model consists of 7 wireframe meshes that represent the three dimensional surfaces of the articulators and the vocal tract walls. 23 parameters determine the shape of the meshes. The articulatory movements in terms of the parameter curves are generated from a gestural description of an utterance. The work presented here is an integral part of a complete articulatory speech synthesizer for high quality synthesis.

This paper presents an animated 2D articulation model of the tongue and the lips for biofeedback applications. The model is controlled by real-time optopalatographic measurements of the positions of the upper lip and the tongue in the anterior oral cavity. The measurement system is an improvement on a previous prototype with increased spatial resolution and an enhanced close-range behavior. The posterior part of the tongue was added to the model by linear prediction. The prediction coefficients were determined and evaluated using a corpus of vocal tract traces of 25 sustained phonemes. The model represents the tongue motion and the lip opening physiologically plausible during articulation in real-time. Index Terms: optopalatography, glossometry, linear prediction, animated vocal tract model, biofeedback