The perception of two vocal qualities in a synthesized vocal utterance: ring and pressed voice

Two vocal qualities, ringquality and pressed quality, were analyzed perceptually. Listeners were asked to rate (on a scale from 0 to 10) the “amount of ring” in one listening and the “amount of pressedness” in another listening. The stimulus was the synthesized utterance /ya-ya-ya-ya-ya/. In the continuum representation of ring, the skewing quotient and the cross section of the epilaryngeal tube area were systematically varied, independently and by a covariation rule. In the continuum representation of pressed, the flow amplitude and open quotient were similarly varied. Results indicated that the crossover point between ring and no ring occurred with an epilaryngeal area of around 1.0 cm², and the crossover point between pressed and not pressed quality occurred at an open quotient of about 0.4. Fundamental frequency also had an effect on the perceptions, with a higher fundamental frequency receiving higher ratings of ring and pressed for otherwise the same parameters. Listeners demonstrated highly variable perceptions in both continua with poor intersubject, intrasubject, and intergroup reliability.     

Vocal tract length perturbation and its application to male-female vocal tract shape conversion

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 Hogskolan, 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.     

A real-time LPC-based vocal tract area display for voice development

This article reports the design and implementation of a graphical display that presents an approximation to vocal tract area in real time for voiced vowel articulation. The acoustic signal is digitally sampled by the system. From these data a set of reflection coefficients is derived using linear predictive coding. A matrix of area coefficients is then determined that approximates the vocal tract area of the user. From this information a graphical display is then generated. The complete cycle of analysis and display is repeated at ≈20 times/s. Synchronised audio and visual sequences can be recorded and used as dynamic targets for articulatory development. Use of the system is illustrated by diagrams of system output for spoken cardinal vowels and for vowels sung in a trained and untrained style     

Characteristics of vocal fold adduction related to voice onset

This study examined whether vocal fold kinematics prior to phonation differed between hard (glottal), normal, or breathy onsets in men and women. Glottal landmarks were identified and digitized from videotape recorded with a rigid laryngoscope during different voice onset types. Significant linear relationships (p 0.0055) were found among onset types on measures of (a) gesture duration when moving from 80% to 20% of maximum distance during adduction, (b) maximum velocity, (c) duration between the completion of adduction and phonation onset, and (d) ratios of maximum velocity to maximum distance between the vocal processes, an estimate of stiffness. The gesture duration was greatest for breathy onsets and least for hard onsets, while the maximum velocity, latency between adduction and phonation onset, and estimated stiffness were greatest for hard onsets and least for breathy onsets. The results suggest that one trajectory seems to be used with increases in gesture duration being accompanied by decreases in articulator stiffness when moving from hard to normal to breathy voice onset types.     

The effect of voice amplification on occupational vocal dose in elementary school teachers

Two elementary school teachers, one with and one without a history of vocal complaints, wore a vocal dosimeter all day at school for a 3-week period. In the second week, each teacher wore a portable voice amplifier. Each teacher showed a reduction in vocal intensity during the week of amplification, with a larger effect for the teacher with vocal difficulties. This teacher also showed a decrease in hourly vocal fold distance dose as measured by the dosimeter despite incurring longer phonation times. Fundamental frequency and vocal fold cycle dose did not appear to be affected by the use of amplification during the teaching day. Both teachers showed evidence of a possible moderate effect of adjusting vocal intensity in the week after amplification, possibly as a means to recalibrate their perceived vocal loudness. This study demonstrates the usefulness of both vocal dosimetry and amplification in monitoring and modifying vocal dose in an occupational setting and reinforces previous data suggesting the effectiveness of amplification in reducing the vocal load in schoolteachers. Implications of the data for future research regarding prevention and treatment of occupational voice disorders are discussed.     

Resonances of a bent vocal tract

Analyses of wave propagation in a vocal tract invariably assume the tract to be a variable area tube with a straight axis. No estimates appear to be available of the effect of curvature of the tract on its resonances (or, equivalently, on its transfer function). For arbitrarily varying cross section, the computation is difficult. However, one can choose an idealized bent vocal tract with a uniform cross section for which the wave equation is separable. The resonance frequencies for such a bent tract are computed and compared to those of the corresponding straight tract. The comparison shows that for typical dimensions of the tract the shift in the resonance frequencies below 4 kHz is in the range of 2%-8%.     

Effect of artificially lengthened vocal tract on vocal fold oscillation's fundamental frequency.

The fundamental frequency of vocal fold oscillation (F(0)) is controlled by laryngeal mechanics and aerodynamic properties. F(0) change per unit change of transglottal pressure (dF/dP) using a shutter valve has been studied and found to have nonlinear, V-shaped relationship with F(0). On the other hand, the vocal tract is also known to affect vocal fold oscillation. This study examined the effect of artificially lengthened vocal tract length on dF/dP. dF/dP was measured in six men using two mouthpieces of different lengths. Results: The dF/dP graph for the longer vocal tract was shifted leftward relative to the shorter one. Conclusion: Using the one-mass model, the nadir of the "V" on the dF/dP graph was strongly influenced by the resonance around the first formant frequency. However, a more precise model is needed to account for the effects of viscosity and turbulence.     

Two-mass models of the vocal cords for natural sounding voice synthesis

Three new two-mass models of the vocal cords are treated. First, the features, structure, and differential equations of motion are described for each of the new models and compared with those of previous models. Second, performances of the models are discussed in terms of glottal volume flow, glottal area, radiated sound pressure, trajectories of mass movement, running spectra of the output sound pressure, and perceptual naturalness of the output sound. Finally, the major effects of glottal source-vocal tract interaction including skewing, truncation, and superposition are investigated, using one of the simplest types of two-mass models and two types of load representing the vocal tract.     

Irregularity of vocal period and amplitude: A first approach to the fractal analysis of voice

Fractal geometry, a relatively young branch of mathematics, offers new ways of evaluating the irregularity of the physiologic and acoustic aspects of speech. The validity and reliability of a box-counting method for estimating the fractal dimension (D_F) of the period and amplitude of vocal signals were demonstrated, and the method was applied to sustained vowels produced by four men and four women. Mean D_F of the fundamental period was 1.46; D_F of the amplitude records averaged a slightly, but significantly, higher 1.54. The potential of D_F as a research and clinical tool is considered.     

Effects of vocal training on the acoustic parameters of the singing voice

Vocal training (VT) has, in part, been associated with the distinctions in the physiological, acoustic, and perceptual parameters found in singers' voices versus the voices of nonsingers. This study provides information on the changes in the singing voice as a function of VT over time. Fourteen college voice majors (12 females and 2 males; age range, 17–20 years) were recorded while singing, once a semester, for four consecutive semesters. Acoustic measures included fundamental frequency (F₀) and sound pressure level (SPL) of the 10% and 90% levels of the maximum phonational frequency range (MPFR), vibrato pulses per second, vibrato amplitude variation, and the presence of the singer's formant. Results indicated that VT had a significant effect on the MPFR. F₀ and SPL of the 90% level of the MPFR and the 90–10% range increased significantly as VT progressed. However, no vibrato or singers' formant differences were detected as a function of training. This longitudinal study not only validates previous cross-sectional research, ie, that VT has a significant effect on the singing voice, but also it demonstrates that these effects can be acoustically detected by the fourth semester of college vocal training.     

Analysis of vocal tract parameters in parkinsonian speech

A method for the analysis of vocal tract parameters is developed, aimed to perform quantitative analysis of rigidity from speech signals of Parkinsonian patients. The cross-sectional area function of the vocal tract is calculated using pitch synchronous autoregressive moving average (ARMA) analysis. The changes in Parkinsonian subjects of the cross-sectional area during the utterance of sustained sounds are attributed to both Parkinsonian tremor and rigidity. In order to isolate the effects of the rigidity on the vocal tract from those of the tremor, an adaptive tremor cancellation (ATC) algorithm is developed, based on the correlation of tremor signals extracted from different locations of the speech production system.     

Dependence of phonation threshold pressure on vocal tract acoustics and vocal fold tissue mechanics

Analytical and computer simulation studies have shown that the acoustic impedance of the vocal tract as well as the viscoelastic properties of vocal fold tissues are critical for determining the dynamics and the energy transfer mechanism of vocal fold oscillation. In the present study, a linear, small-amplitude oscillation theory was revised by taking into account the propagation of a mucosal wave and the inertive reactance (inertance) of the supraglottal vocal tract as the major energy transfer mechanisms for flow-induced self-oscillation of the vocal fold. Specifically, analytical results predicted that phonation threshold pressure (Pth) increases with the viscous shear properties of the vocal fold, but decreases with vocal tract inertance. This theory was empirically tested using a physical model of the larynx, where biological materials (fat, hyaluronic acid, and fibronectin) were implanted into the vocal fold cover to investigate the effect of vocal fold tissue viscoelasticity on Pth. A uniform-tube supraglottal vocal tract was also introduced to examine the effect of vocal tract inertance on Pth. Results showed that Pth decreased with the inertive impedance of the vocal tract and increased with the viscous shear modulus (G") or dynamic viscosity (eta') of the vocal fold cover, consistent with theoretical predictions. These findings supported the potential biomechanical benefits of hyaluronic acid as a surgical bioimplant for repairing voice disorders involving the superficial layer of the lamina propria, such as scarring, sulcus vocalis, atrophy, and Reinke's edema.     

The relationship among voice onset, voice quality, and fundamental frequency: a dynamical perspective

In dynamical motor theory, skill acquisition occurs as a modification of preexisting coordination patterns or attractor states. The purpose of this study was to assess how different levels of voice onset, voice quality, and fundamental frequency (F₀) combine to form the attractor states common to voice motor control. Three levels of voice onset (glottal, simultaneous, and breathy), voice quality (modal speech, mixed, and falsetto), and fundamental frequency (low, mid, and high) were manipulated by vocally untrained, female subjects. Percent correct of acquisition trials and self-report of effort were used as measures of stable phonations indicative of an attractor state. Using intensity as a covariate, the results provided support for two of the three predicted triads representing attractor states in female speakers: (1) glottal onset/modal speech quality/low F₀; and (2) breathy onset/falsetto quality/high F₀. The results of this study suggest that certain parameters of voice motor control, such as onset, quality, and F₀, exist as part of a dynamical system that can be identified and manipulated in voice motor acquisition and learning.     

利用声带动力学模型参数反演方法进行病变嗓音分类

提出一种声带动力学模型参数反演方法,从发声机理角度对声带病变嗓音进行有效区分。依据声带生理组织和伯努利定律构建声带动力学模型,确定模型优化参数向量,耦合声门气流获取模型声门波;利用迭代自适应逆滤波算法获得实际嗓音声门波作为目标声门波;采用遗传优化算法提出通过匹配目标和模型声门波特征参数实现模型参数反演。实验结果表明,表征声门波的各时频域参数匹配相对误差不超过2%;依据反演所获模型参数提出去除声门下压影响的平均归一化缩放系数,克服声带非对称性特征在区分病变嗓音方面的不足,实现病理嗓音的全面有效区分。     

Resonances of a branched vocal tract with compliant walls

The calculation of the resonance frequencies from experimental cross-sectional areas of a vocal tract under the assumption that its walls are perfectly rigid provides values that noticeably differ from the measured resonance frequencies. The compliance of the walls affects the first resonance and almost does not affect the higher-order resonances. The presence of branching in the tract at the level of the larynx affects the second and third resonances stronger than the first resonance. The parameters of the wall impedance (the loss, mass, and elasticity) and the length and cross-sectional area of the branchings are determined by minimizing the rms discrepancy between the measured and calculated resonance frequencies. The error in the frequency calculation with allowance for the wall compliance and branching in the tract proves to be within the accuracy of the formant estimation.     

Comparison of vocal tract formants in singing andnonperiodic phonation

The skilled use of nonperiodic phonation techniques in combination with spectrum analysis has been proposed here as a practical method for locating formant frequencies in the singing voice. The study addresses the question of the degree of similarity between sung phonations and their nonperiodic imitations, with respect to both frequency of the first two formants as well as posture of the vocal tract. Using magnetic resonance imaging (MRI), linear predictive coding (LPC), and spectrum analysis, two types of nonperiodic phonation (ingressive and vocal fry) are compared with singing phonations to determine the degree of similarity/difference in acoustic and spatial dimensions of the vocal tract when these phonation types are used to approximate the postures of singing. In comparing phonation types, the close similarity in acoustic data in combination with the relative dissimilarity in spatial data indicates that the accurate imitations are not primarily the result of imitating the singing postures, but have instead an aural basis.     

基于嗓音源变换函数的声门发声效率估计方法

在澄清嗓音源概念的基础上提出了一种以嗓音源变换函数为基础的声门发声效率估计方法。将嗓音源变换函数定义为声门上声学嗓音源与声门气流体积速度波在频域上的比值。通过精心设计的活体犬喉及人体发声实验分别在不同元音、压紧嗓音、气声、假声和典型喉病变条件下。采用稳态元音发声方式对这一新的声门发声效率估计方法实验研究;并与其他发声效率方法综合比较。结果表明,该方法能消除上声道传输与共鸣作用的影响,能反映不同发声方式的差异;频域平均声门发声效率反映了物理定义上的声门发声效率的变化,而声门基频发声效率的变化与AC/DC比值变化一致。     

Aerodynamic and acoustic voice measurements of patients with vocal nodules: variation in baseline and changes across voice therapy.

An important clinical issue concerns the efficacy of current voice therapy approaches in treating voice disorders, such as vocal nodules. Much research focuses on finding reliable methods for documentation of treatment results. In this second treatment study of ten patients with vocal nodules, who participated in a behaviorally based voice therapy program, 11 aerodynamic (transglottal air pressure and glottal waveform) and acoustic (spl, f0, and spectrum slope) measures were used. Three pretherapy baseline assessments were carried out, followed by one assessment after each of five therapy phases. Measurements were made of two types of speech materials: Strings of repeated /pae/ syllables and sustained /ae/ phonations in two loudness conditions: comfortable loudness and loud voice. The data were normalized using z-scores, which were based on data from 22 normal subjects. The results showed that the aerodynamic measures reflected the presence of vocal pathology to a higher degree than did the acoustic spectral measures, and they should be useful in studies comparing nodule and normal voice production. Large individual session-to-session variation was found for all measures across pretherapy baseline recordings, which contributed to nonsignificant differences between baseline and therapy data.