Ilse B. Labuschagne’s research while affiliated with University of British Columbia and other places

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Publications (5)


Noise thresholds in harmonic series maskers
  • Article

April 2021

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18 Reads

The Journal of the Acoustical Society of America

Ilse B. Labuschagne

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Valter Ciocca

The presence of noise is a salient cue to the perception of breathiness and aspiration in speech sounds. The detection of noise within harmonic series (maskers) composed of unresolved components was found to depend on the fundamental frequency (fo) and the overall level of the masker [Gockel, Moore, and Patterson (2002). J. Acoust. Soc. Am., 111 (6), 2759–2770]. In the present study, noise detection thresholds were measured as a function of the frequency range, the fo, and the overall level of harmonic maskers. Frequency range was specified in equivalent rectangular bandwidth (ERB) units (3–13, 13–23, 23–33, or 3–33 ERBs). The results were consistent with the idea that listeners rely on spectral cues when maskers comprise only resolved components (3–13 ERBs), and on temporal (dip listening) cues when maskers contain only unresolved components (23–33 ERBs). Noise detection thresholds were generally lower when masker level was high (70 dBA) than when it was low (50 dBA). Masker fo affected thresholds only when listeners relied on spectral cues for noise detection. With the wideband (3–33 ERBs) masker, listeners likely detected noise by focusing on the frequency band (23–33 ERBs) with the most advantageous noise-to-harmonic ratio.


The effect of vocal tract parameters on aspiration noise discrimination

February 2020

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20 Reads

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2 Citations

The Journal of the Acoustical Society of America

Previous research showed that aspiration noise difference limens in moderately breathy /a/ vowels decreased as the spectral slope of the glottal source spectrum became increasingly steep [Kreiman and Gerratt, J. Acoust. Soc. Am. 131(1), 492–500 (2012)]. The current study investigated whether discrimination of aspiration noise levels was affected by differences in spectral shape due to vowel quality (/æ/ and /i/) and speaker identity (three male speakers) when the slope of the glottal source spectrum was fixed. The results showed that discrimination performance was worse overall for /i/ than /æ/, but the result may have resulted from relatively poor performance for the /i/ vowel of one speaker. Acoustic analyses of the stimuli were performed to estimate the association between acoustic properties and the perceptual outcomes. The results showed that both the smoothed cepstral peak prominence and the harmonic energy level between 2 and 5 kHz may account for the observed differences in aspiration noise discrimination among speakers within each vowel, but not for differences between vowel categories. It is possible that the relationship between the aspiration noise discrimination and aforementioned acoustic properties may be modulated by the spectral distribution of energy across frequency.


Thresholds of noise in harmonic series maskers

September 2018

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8 Reads

The Journal of the Acoustical Society of America

Numerous studies have investigated the detection of pure tones and harmonic series in noise, but far fewer studied the perception of noise in harmonic series. One such study [Gockel, Moore and Patterson, J. Acoust. Soc. Am., 111(6), 2759–2770 (2002)] demonstrated that the masking thresholds of noise in harmonic series maskers were affected by the fundamental frequency (F0) and the overall level of the series, and by the relative phase of the harmonic components. The maskers used by Gockel et al. comprised unresolved harmonics (10th and higher harmonics below 5 kHz) for which F0 and frequency range covaried. The current study investigated noise detection for three non-overlapping spectral bands of equal auditory filter bandwidths (ERBs). Bands included either resolved harmonics (B1), unresolved harmonics (B3), or both resolved and unresolved harmonics (B2). Masker F0 and overall level were also varied. A Bayesian linear mixed-effects analysis showed that noise detection was better for higher F0s in B1 and B2, and that a higher presentation level resulted in a small improvement in noise detection in B2. Noise detection was better for higher presentation levels in B3. The findings will be discussed in relation to predictions of auditory processing models [Patterson, Allerhand, Giguère, J. Acoust. Soc. Am. 98(4), 1890–1894 (1995)].



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

September 2016

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61 Reads

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11 Citations

Acoustical Science and Technology

Research on the acoustic correlates of breathiness has been plagued by a lack of consistent findings across studies and low intra- and inter-rater agreement. Sources of variability can arise from different sources including: differences in stimulus types (recorded or synthesized); differences in speaker groups (for recorded stimuli) or in synthesis parameters (for synthesized stimuli); differences in experimental methodologies (task type, number of repetitions, listener backgrounds and experience). This review discussed these sources of variability, and described solutions that have the potential to address the variability and the inconsistencies often reported in the literature. A critical appraisal of the evidence about the relative importance of various acoustic measures resulted in the identification of measures of periodicity, noise content, and high-to-low frequency energy as the most likely acoustic correlates of breathiness.

Citations (2)


... For this reason, formant frequencies and bandwidths were re-adjusted to provide the best possible match to the natural target voice in the context of each of the 3 new harmonic sources, so that any mismatches in overall quality between the synthetic and natural tokens could be unambiguously attributed to differences among source models. Levels for the noise-to-harmonics ratio were also reset, to compensate for changes in the perceptual prominence of spectral noise as a result of changes to the harmonic source spectrum (Kreiman and Gerratt, 2012;Labuschagne and Ciocca, 2020). All other model parameters remained unchanged from their values in experiment 1. ...

Reference:

Validating a psychoacoustic model of voice quality
The effect of vocal tract parameters on aspiration noise discrimination
  • Citing Article
  • February 2020

The Journal of the Acoustical Society of America

... To give an example of how a column is filled up in Table I, lets look at the voice quality of 'Breathiness'. [32]- [35] demonstrates that breathiness has a negative correlation with loudness, alphaRatio (the ratio of the summed energy from 50-1000 Hz and 1-5 kHz), hammerbergIndex (the ratio of the strongest energy peak in the 0-2 kHz region to the strongest peak in the 2-5 kHz region), a positive correlation with spectral flux (a measure of the change in the spectral content of a sound over time), has a positive correlation with F1, F2 and F3 bandwidth and [36] shows that breathiness has a negative correlation with F2 and F3 frequency. ...

The perception of breathiness: Acoustic correlates and the influence of methodological factors
  • Citing Article
  • September 2016

Acoustical Science and Technology