Voice quality variations include a set of voicing sound source modifications ranging from laryngealized to normal to breathy phonation. Analysis of reiterant imitations of two sentences by ten female and six male talkers has shown that the potential acoustic cues to this type of voice quality variation include: (1) increases to the relative amplitude of the fundamental frequency component as open quotient increases; (2) increases to the amount of aspiration noise that replaces higher frequency harmonics as the arytenoids become more separated; (3) increases to lower formant bandwidths; and (4) introduction of extra pole zeros in the vocal-tract transfer function associated with tracheal coupling. Perceptual validation of the relative importance of these cues for signaling a breathy voice quality has been accomplished using a new voicing source model for synthesis of more natural male and female voices. The new formant synthesizer, KLSYN88, is fully documented here. Results of the perception study indicate that, contrary to previous research which emphasizes the importance of increased amplitude of the fundamental component, aspiration noise is perceptually most important. Without its presence, increases to the fundamental component may induce the sensation of nasality in a high-pitched voice. Further results of the acoustic analysis include the observations that: (1) over the course of a sentence, the acoustic manifestations of breathiness vary considerably--tending to increase for unstressed syllables, in utterance-final syllables, and at the margins of voiceless consonants; (2) on average, females are more breathy than males, but there are very large differences between subjects within each gender; (3) many utterances appear to end in a "breathy-laryngealized" type of vibration; and (4) diplophonic irregularities in the timing of glottal periods occur frequently, especially at the end of an utterance. Diplophonia and other deviations from perfect periodicity may be important aspects of naturalness in synthesis.

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Analysis, synthesis, and perception of voice quality variations among female and male talkers

The purpose of this study was to evaluate the effectiveness of several acoustic measures in predicting breathiness ratings. Recordings were made of eight normal men and seven normal women producing...

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Acoustic Correlates of Breathy Vocal Quality

In an earlier study, we evaluated the effectiveness of several acoustic measures in predicting breathiness ratings for sustained vowels spoken by nonpathological talkers who were asked to produce nonbreathy, moderately breathy, and very breathy phonation (Hillenbrand, Cleveland, & Erickson, 1994). The purpose of the present study was to extend these results to speakers with laryngeal pathologies and to conduct tests using connected speech in addition to sustained vowels. Breathiness ratings were obtained from a sustained vowel and a 12-word sentence spoken by 20 pathological and 5 nonpathological talkers. Acoustic measures were made of (a) signal periodicity, (b) first harmonic amplitude, and (c) spectral tilt. For the sustained vowels, a frequency domain measure of periodicity provided the most accurate predictions of perceived breathiness, accounting for 92% of the variance in breathiness ratings. The relative amplitude of the first harmonic and two measures of spectral tilt correlated moderately with breathiness ratings. For the sentences, both signal periodicity and spectral tilt provided accurate predictions of breathiness ratings, accounting for 70%-85% of the variance.

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Acoustic Correlates of Breathy Vocal Quality: Dysphonic Voices and Continuous Speech

The aim of the research reported in this paper is to formulate a set of acoustic parameters of the voicing source that reflect individual differences in the voice qualities of female speakers. Theoretical analysis and observations of experimental data suggest that a more open glottal configuration results in a glottal volume-velocity waveform with relatively greater low-frequency and weaker high-frequency components, compared to a waveform produced with a more adducted glottal configuration. The more open glottal configuration also leads to a greater source of aspiration noise and larger bandwidths of the natural frequencies of the vocal tract, particularly the first formant. These different attributes of the glottal waveform can be measured directly from the speech spectrum or waveform. A set of acoustic parameters that are likely to indicate glottal characteristics is described. These parameters are measured in the speech of a group of female speakers, and the glottal configurations of the speakers are hypothesized. This research contributes to the description of normal variations of voicing characteristics across speakers and to a continuing effort to improve the analysis and synthesis of female speech. It may also have applications in clinical settings.

Glottal characteristics of female speakers: Acoustic correlates

Voice diseases have been increasing dramatically in recent times due mainly to unhealthy social habits and voice abuse. These diseases must be diagnosed and treated at an early stage, especially in the case of larynx cancer. It is widely recognized that vocal and voice diseases do not necessarily cause changes in voice quality as perceived by a listener. Acoustic analysis could be a useful tool to diagnose this type of disease. Preliminary research has shown that the detection of voice alterations can be carried out by means of Gaussian mixture models and short-term mel cepstral parameters complemented by frame energy together with first and second derivatives. This paper, using the F-Ratio and Fisher's discriminant ratio, will demonstrate that the detection of voice impairments can be performed using both mel cepstral vectors and their first derivative, ignoring the second derivative

Dimensionality Reduction of a Pathological Voice Quality Assessment System Based on Gaussian Mixture Models and Short-Term Cepstral Parameters

In order to evaluate noise components included in pathologic voice signals, a novel acoustic measure, normalized noise energy (NNE), is proposed and its effectiveness for the detection of laryngeal pathologies is investigated with 250 vowel samples spoken by 64 control (normal) subjects and 186 patients with various laryngeal diseases. The NNE is automatically computed from the voice signals using an adaptive comb filtering method performed in the frequency domain. Experiments with the voice samples show that the NNE is especially effective for detecting glottic cancer, recurrent nerve paralysis, and vocal cord nodules. Specifically, when glottic cancer is represented in terms of the T classification adopted by the UICC (Union Internationale Contre le Cancer), glottic T2-T4 cancer can be perfectly discriminated from normal samples, but 22.6% of patients with glottic T1 cancer are incorrectly classified as normal, with an error rate of 9.4% for normal subjects.

Normalized noise energy as an acoustic measure to evaluate pathologic voice

Longitudinal changes were investigated for selected voice source parameters: fundamental frequency (F0), jitter (period perturbation quotient, PPQ), shimmer (amplitude perturbation quotient, APQ) and glottal noise (normalized noise energy, NNE). Acoustic analyses were made on the sustained phonation of the Japanese vowel /a/ of 20 males and 38 females with no laryngeal disease, which were recorded over periods ranging from 10 to 18 years. The longitudinal change of the parameters was evaluated by the statistical t-test, revealing that: 1) strong individuality existed for significant longitudinal changes in the acoustic parameters, 2) F0 falling is a more typical tendency of vocal aging of females than males, while F0 rising, which has been pointed out in the previous reports for males, was not found, 3) shimmer is a more observable indication of vocal aging than jitter, and 4) glottal noise in a high-frequency region tends to increase with aging.

Satoshi Ebihara

Papers

Normalized noise energy as an acoustic measure to evaluate pathologic voice

Longitudinal changes of selected voice source parameters.