gms | German Medical Science

25. Wissenschaftliche Jahrestagung der Deutschen Gesellschaft für Phoniatrie und Pädaudiologie e. V.

Deutsche Gesellschaft für Phoniatrie und Pädaudiologie e. V.

12.09. - 14.09.2008, Düsseldorf

How to minimise gender and voice intensity effects in acoustic assessments

Wie der Einfluss von Geschlecht und Lautstärke in der klinischen akustischen Stimmuntersuchung minimiert werden kann

Vortrag

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  • corresponding author presenting/speaker Meike Brockmann - Abt. Phoniatrie-Klinische Logopädie, ORL Klinik, Universitätsspital Zürich, Zürich, Schweiz
  • author Michael J. Drinnan - Critical Care Physics, Medical Physics, General Hospital Newcastle upon Tyne, Newcastle upon Tyne, Großbritannien
  • author Paul N. Carding - Dept. of Speech, Voice and Swallowing, Freeman Hospital, Newcastle University, Newcastle upon Tyne, Großbritannien

Deutsche Gesellschaft für Phoniatrie und Pädaudiologie. 25. Wissenschaftliche Jahrestagung der Deutschen Gesellschaft für Phoniatrie und Pädaudiologie. Düsseldorf, 12.-14.09.2008. Düsseldorf: German Medical Science GMS Publishing House; 2008. Doc08dgppV49

Die elektronische Version dieses Artikels ist vollständig und ist verfügbar unter: http://www.egms.de/de/meetings/dgpp2008/08dgpp66.shtml

Veröffentlicht: 27. August 2008

© 2008 Brockmann et al.
Dieser Artikel ist ein Open Access-Artikel und steht unter den Creative Commons Lizenzbedingungen (http://creativecommons.org/licenses/by-nc-nd/3.0/deed.de). Er darf vervielf&aauml;ltigt, verbreitet und &oauml;ffentlich zug&aauml;nglich gemacht werden, vorausgesetzt dass Autor und Quelle genannt werden.


Zusammenfassung

Various reports have shown marked gender and habitual voice intensity effects on jitter and shimmer measurements in clinical practice. The aim of this cross-sectional single cohort study was to compare voice intensity and gender effects in healthy adults under a range of assessment protocols, and to derive guidelines to control for these effects in practice.

Forty healthy adults (1:1 f:m) aged 20–40 years were recorded. All phonated a prolonged /a/ under eleven protocols: a) at subjective soft, normal and loud intensity to model routine clinical assessment b) at prescribed intensities: 65, 75, 85 and 95 dB, maintained by visual feedback; c) at prescribed intensities and with fixed fundamental frequency (auditory feedback). Recordings were analysed with Praat software. Gender effects were assessed with inferential (ANOVA) statistics.

Lowest jitter and shimmer were found at highest SPL. The difference between male and female measurements was smallest with control for SPL but not for pitch. When asked for soft, medium or loud phonations without SPL control, men were always louder. But at prescribed voice intensities women and men phonated comparably loud; 75 dB and 85 dB were matched best. Inter-individual SPL differences, and therefore also jitter and shimmer differences were considerably lower in controlled phonations.

Gender and habitual voice intensity effects in voice measurements can be efficiently minimised by asking the patients to control for voice intensity by visual feedback. In acoustic assessments patients should maintain their voice intensity at 85 dB. Future work should investigate which patients groups are able to fulfil these requirements.


Text

Introduction

The aim of this study was to compare voice intensity and gender effects on jitter and shimmer in healthy adults under eleven clinically realistic protocols and to derive guidelines to control for these effects in practice. Investigated were phonations at subjectively soft, medium and loud voice intensity levels, at four different prescribed voice intensity levels and at prescribed intensity levels with control of fundamental frequency (FF).

Objective acoustic assessments form part of a comprehensive voice examination protocol and indirectly assess the vibratory properties of the vocal folds [1], [2]. Jitter and shimmer measure FF and voice intensity variation from one vocal fold vibration to the next. Acoustic measurements are mainly done in vowel phonations at subjectively “comfortable” voice loudness. However various reports have shown marked gender and voice intensity effects on jitter and shimmer in healthy and dysphonic voices. Higher voice intensities were generally associated with dramatically lower jitter and shimmer [3], [4], [5]. Even the habitual intensity differences between individuals at “comfortable” or “medium” voice loudness may influence clinical jitter and shimmer measurements considerably. In addition gender effects appear to be mainly linked to different habitual voice loudness levels between women and men when asked to phonate at “comfortable” voice intensity [6], [7]. This clearly reduces the diagnostic value and usefulness of acoustic assessments. We believe that current assessment guidelines are not sufficient to control for voice intensity and gender effects in clinical practice, the aim addressed in this work.

Materials

A total of 40 participants from 20 to 39 years, 20 women with a mean age of 28;3 years, and 20 men with a mean age of 30;1 years, were included in this cross-sectional single cohort study. Participants were excluded if they met one or more the following criteria: (a) a hoarse voice on the day of recording, (b) recent voice problems or a voice disorder history, (c) any previous formal voice training or voice therapy, (d) medication or a medical condition that might affect normal voice function, (e) recent intubation for any surgical intervention, (f) surgery in the torso, head and neck region in the last 18 months, (g) inability to phonate /a/ for 5 seconds. The native language (usually Swiss German or High German) and smoking habits of all participants was noted. Each subject provided 22 phonations, giving a total of 880 individual phonations for acoustic analysis.

Methods

All voice recordings were made in a sound proof room. The microphone was head-mounted at 10 cm distance from the mouth and positioned laterally. Audacity [8] was used to record onto a laptop with a sampling rate of 48000 Hz and 24-bit resolution. Calibration of the recording system was performed with Speech Weighted Noise [9] at different intensities ranging from 65 dB to 95 dB (10 dB steps).

All participants phonated the vowel /a/ for 5 seconds under eleven protocols: (a) at subjective soft, normal and loud intensity to model routine clinical assessment; (b) at prescribed intensity levels of 65, 75, 85 and 95 dB; to control their voice intensity all participants could see a Sound Pressure Level meter with the prescribed intensity levels (visual feedback); (c) at 65, 75, 85 and 95 dB (also with visual feedback) but with a fixed fundamental frequency at their own habitual pitch; for this, the mean FF was analysed from 3 seconds of normal speech, the measured tone was played to the participants by piano (auditory feedback).

Acoustic analysis was conducted with Praat [10] using second 0.5 to 3.5 from voice onset. Voice perturbation parameters measured from each phonation were “jitter %” and “shimmer %”. The effects of phonation task (the 11 protocols) and gender (f/w) on voice SPL, FF, jitter % and shimmer % were assessed using descriptive and inferential statistics (ANOVA).

Results

Lowest jitter and shimmer were found at highest SPL in all phonatory tasks.

When asked for soft, medium or loud phonations without SPL control, men were always louder. But at prescribed voice intensities women and men phonated comparably loud. 75 dB and 85 dB were matched best and could be produced by most participants. Around half of all participants were not able to keep their own pitch at 65 and 95 dB.

Inter-individual SPL differences, and therefore also jitter and shimmer differences were considerably lower in controlled phonations. The difference between male and female jitter and shimmer measurements was smallest with control for SPL but not for pitch (Figure 1 [Fig. 1], Figure 2 [Fig. 2]). Women had lower jitter and shimmer in phonations at prescribed SPL.

Discussion

Gender and habitual voice intensity effects in acoustic measurements can be efficiently minimised by asking the patients to control for voice intensity by visual feedback. However controlling voice intensity and FF at the same time is not achievable for a number of adults with normal voices especially at 65 and 95 dB. In acoustic assessments patients should maintain their voice intensity at 85 dB without control of FF. Future work should investigate which patients groups are able to fulfil these requirements.


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