Perception Of Breathiness Research Articles

Prolegomena to a special volume on South Asian phonetics and phonology

Abstract This chapter is a short thematic introduction to the papers that appear in this special volume on the phonetics and phonology of a selective but representative set of languages from the South Asian sprachbund. The volume consists of five papers that engage with a broad set of topics, namely, acoustics of Kalasha affricates, perception of breathiness in Gujarati, syllable structure of Kuki-Chin, syllable structure and incipient vowels in Lamkang, and vowel harmony in Assamese. These papers, we hope, are representative in terms of the choice of theoretical frameworks and methodologies employed in addressing the various linguistic phenomena.

気息性の知覚 ――音響関連量について，また方法論的要因による影響――

気息性の知覚 ――音響関連量について，また方法論的要因による影響――

The perception of breathiness: Acoustic correlates and the influence of methodological factors

The perception of breathiness: Acoustic correlates and the influence of methodological factors

Acoustic models of co-varying vocal roughness and breathiness

Dysphonia is characterized by several vocal qualities including breathiness and roughness. These qualities can coexist within a single voice. To examine the potential interaction between judgments of one voice quality in the presences of another, a large set of synthetic voices that co-varied along the breathiness and roughness continua were created and evaluated by 10 listeners. The perception of roughness (synthesized via amplitude modulation) was unaffected by degree of breathiness. The perception of breathiness, however, was affected by the degree of roughness: for low-breathy voices breathiness increased by about 2 dB as roughness increased from no roughness to maximum roughness; yet for high-breathy voices, breathiness decreased by about 2 dB as roughness increased. Current acoustic models of voice quality (pitch strength, auto-correlation peak, cepstral peak, partial loudness ratio, and glottal-noise-excitation ratio) do not explain the observed interaction of roughness and breathiness. To explain the observed interaction, we evaluate the possibility that roughness perception is dominated by temporal cues (which are unaffected by the presence of breathiness) and that breathiness perception is driven by spectro-temporal cues which are affected by the sub-harmonics generated by amplitude modulation. The sub-harmonics partially contribute to non-harmonic energy (increasing breathiness) and partially mask aperiodic energy (decreasing breathiness).

Perception of breathiness in pediatric speakers

Extensive research has been done to determine acoustic metrics for voice quality. However, few studies have focused on voice quality in the pediatric population. Instead, metrics evaluated on adults have directly been applied to children’s voices. Some variables, such as pitch, that differ between adult and pediatric voices, have been shown to be critical in the perception of breathiness. Furthermore, it is not known whether adults perceive voice quality similarly for pediatric and adult speakers. In this experiment, 10 listeners judged breathiness for 28 stimuli using a single-variable matching task. The stimuli were modeled after four pediatric speakers and synthesized using a Klatt-synthesizer to have a wide range of aspiration noise and open quotient. Both of these variables have been shown to influence the perception of breathiness. The resulting data were compared to that previously obtained for adult speakers using the same matching task. Comparison of adult and pediatric voices will help identify differences in the perception of breathiness for these groups of speakers and to develop more accurate metrics for voice quality in children. [Research supported by NIH (R01 DC009029).]

A model for the prediction of breathiness in vowels

The perception of breathiness in vowels is cued by multiple acoustic cues, including changes in aspiration noise (AH) and the open quotient (OQ) [Klatt and Klatt, J. Acoust. Soc. Am. 87(2), 820-857 (1990)]. A loudness model can be used to determine the extent to which AH masks the harmonic components in voice. The resulting "partial loudness" (PL) and loudness of AH ["noise loudness" (NL)] have been shown to be good predictors of perceived breathiness [Shrivastav and Sapienza, J. Acoust. Soc. Am. 114(1), 2217-2224 (2003)]. The levels of AH and OQ were systematically manipulated for ten synthetic vowels. Perceptual judgments of breathiness were obtained and regression functions to predict breathiness from the ratio of NL to PL (η) were derived. Results show that breathiness can be modeled as a power function of η. The power parameter of this function appears to be affected by the fundamental frequency of the vowel. A second experiment was conducted to determine if the resulting power function could estimate breathiness in a different set of voices. The breathiness of these stimuli, both natural and synthetic, was determined in a listening test. The model estimates of breathiness were highly correlated with perceptual data but the absolute predicted values showed some discrepancies.

Evaluating a model to estimate breathiness in vowels

The perception of breathiness in vowels is cued by changes in aspiration noise (AH) and the open quotient (OQ) [Klatt and Klatt, J. Acoust. Soc. Am. 87(2), 820–857 (1990)]. A loudness model can be used to determine the extent to which AH masks the harmonic components in voice. The resulting partial loudness (PL) and loudness of AH (noise loudness; NL) have been shown to be good predictors of perceived breathiness [Shrivastav and Sapienza, J. Acoust. Soc. Am. 114(1), 2218–2224 (2005)]. The levels of AH and OQ were systematically manipulated for ten synthetic vowels. Perceptual judgments of breathiness were obtained and regression functions to predict breathiness from NL/PL were derived. Results show breathiness to be a power function of NL/PL when NL/PL is above a certain threshold. This threshold appears to be affected by the stimulus pitch. A second experiment was conducted to determine if the resulting power function could be used to estimate breathiness in natural voices. The breathiness of novel stimuli, both natural and synthetic, was determined in a listening test. For comparison, breathiness for the same stimuli was also estimated using the power function obtained previously. Results show the extent to which findings can be generalized. [Research supported by NIH/R21DC006690.]

Predicting changes in breathiness resulting from variations in aspiration noise and open quotient using a loudness model

Previous studies have reported that increases in high-frequency aspiration noise (AH) and open quotient (OQ) are correlated with an increase in the perception of breathiness in vowels [Klatt and Klatt, J. Acoust. Soc. Am. 87, 820–857 (1990)]. However, a system based on psychoacoustic loudness models has been shown to predict the level of breathiness in vowels to a greater extent than AH and OQ themselves [Shrivastav and Sapienza, J. Acoust. Soc. Am. 114, 2217–2224 (2003)]. The goal of this experiment was to verify the significance of AH and OQ in the perception of breathiness and to determine how each of these influences the output of the loudness model, individually and in combination. Ten vowels, five male and five female, were synthesized using a Klatt synthesizer. Each vowel was used to generate three continua varying in terms of their OQ and/or AH. Ten listeners rated breathiness for each continuum using a magnitude estimation task. Results show that normalized partial loudness as well as the loudness of aspiration noise predicted changes in breathiness resulting from an increase in AH. Increase in OQ resulted in very small changes in perceived breathiness, resulting in poor correlation with loudness measures. [Research supported by NIH/R21DC006690.]

Effects of spectral slope on perceived breathiness in vowels

Previous studies have indicated that breathiness is correlated with changes in spectral slope as well as aspiration noise [Klatt & Klatt, ‘‘Analysis, synthesis, and perception of voice quality variations among female and male talkers,’’ J. Acoust. Soc. Am. 87, 820–857 (1990)]. In a recent study, Shrivastav and Pinero [Shrivastav & Pinero ‘‘Effect of aspiration noise and spectral slope on perceived breathiness in vowels,’’ J. Acoust. Soc. Am. 117, 2622 (2005)] observed that varying spectral slope resulted in minimal changes on the perceived breathiness for synthetic vowels. However, the stimuli tested in this experiment included a relatively narrow range of spectral slope variation. The goal of the present experiment was to verify the role of spectral slope on the perception of breathiness by testing stimuli that had a wider range of variation in spectral slope. Ten voices (5 male and 5 female) were synthesized using a Klatt synthesizer. Each of these was manipulated to generate two continua varying in their spectral slope from −3 to −30 dB/octave. One continuum had a constant cutoff frequency of 500 Hz, while the other continuum had a cutoff frequency between the second harmonic (H2) and the third harmonic (H3). Ten listeners judged the degree of breathiness using a 7-point rating scale. Preliminary results suggest that spectral slope has minimal effect on the perception of breathiness in synthetic vowels. [Research supported by NIH/R21 DC006690.]

Multidimensional Scaling of Breathy Voice Quality: Individual Differences in Perception

Experiments on disordered voice quality with multidimensional scaling (MDS) have resulted in solutions with low R-square and have failed to show consistent dimensions across different listeners. These findings have been suggested to indicate large individual differences in the perception of voice quality. However, these inconsistencies may originate from several factors, including random stimulus selection, instructions that encourage listeners to respond to global difference in pairs of voices, and noisy perceptual data. This experiment used MDS techniques to study individual differences in perception of breathiness. The voices in the experiment were selected to have a relatively wide variation in breathiness but only minimal variation in roughness, strain, and fundamental frequency. Additionally, listeners were instructed specifically to rate similarities in breathiness rather than judging global differences in voices, and several judgments from each listener were averaged to minimize noise in the data. It was hypothesized that these modifications would result in an MDS solution that accounted for greater variance in perceptual data than previously shown. Results show that averaging multiple responses from each listener increased the R-square from 45% to approximately 75%. The poor R-square and large individual differences in voice quality perception observed in past research may have partly resulted from the experimental procedures in previous studies. These findings suggest that individual differences in the perception of voice quality are not as large as previously thought, and a model of voice quality perception for an "average" listener may be a good representation for the general population.

Effect of aspiration noise and spectral slope on perceived breathiness in vowels

Breathy voice quality is frequently encountered in both normal and dysphonic voices. Breathiness has been associated with an increase in the intensity of aspiration noise as well as changes in spectral slope [Childers and Ahn, 1995; Fischer-Jorgenson, 1967; Huffman, 1987; Klatt and Klatt, 1990]. Shrivastav and Sapienza (2003) found that subjective ratings of breathiness obtained from a group of listeners were highly correlated with certain measures calculated from the auditory spectrum of the vocal acoustic signal. One of these measures, the partial loudness of the harmonic energy, was related to both the aspiration noise and the spectral slope of the voices. In the present experiment, 10 young adult listeners with normal hearing were presented with voices that varied systematically in terms of their aspiration noise and spectral slope. The stimuli, five male and five female voices, were generated using the Klatt synthesizer and were modeled after naturally occurring voices. Listeners rated breathiness for each of these stimuli using a 7-point rating scale. Results show the relative contribution of spectral slope and aspiration noise to the perception of breathiness.

A new index for evaluation of the turbulent noise in pathological voice.

The validity of the parameter Br index, which was designed as an indicator of the turbulent noise in breathy voice, was tested. The parameter was determined by the ratio between energy of the second derivative of the high-pass filtered wave and that of the nonderived high-pass filtered wave. The principle of this method is the utilization of the difference in the frequency range between the turbulent noise and other components present. The parameter was found to correlate with the perception of breathiness. Clinical applications of this index suggest the possibility of using it further as a detection tool for diseases that generate turbulent noises.