Purpose: The aim of this study was to investigate voice loudness and gender effects on jitter and shimmer in healthy young adults, since previous descriptions have been inconsistent.
Method: Fifty-seven healthy adults (28 women, 29 men) aged 20 to 40 years were included in this cross-sectional single cohort study. Three phonations of /a/ at soft, medium and loud individual loudness were recorded and analysed using Praat (software). Voice loudness and gender effects on measured sound pressure level, fundamental frequency, jitter and shimmer were assessed using descriptive and inferential (ANOVA) statistics.
Results: Jitter and shimmer significantly increased with decreasing voice loudness, especially in phonations below 75 dB and 80 dB. In soft and medium phonation, males were generally louder and showed significantly less shimmer. However, men had higher jitter measures when phonating softly. Gender differences in jitter and shimmer at medium loudness may be mainly linked to different habitual voice loudness levels.
Conclusions: This pragmatic study shows significant voice loudness and gender effects on perturbation. In clinical assessment, requesting phonations above 80 dB, at comparable loudness between gender, would enhance measurement reliability. However, voice loudness and gender effects in other age-groups, in disordered voices, or when a minimal loudness is requested, should be further investigated.
Brockmann M, Storck C, Carding P, Drinnan MJ. Voice loudness and gender effects on jitter and shimmer in healthy adults. Journal of Speech, Language and Hearing Research 2008; 50: In press.
Dr. Michael J. Drinnan, Freeman Unit, Newcastle upon Tyne. Tel: +44 (0)191-223-6161.
Regional Medical Physics Department, Freeman Hospital, Newcastle upon Tyne, NE7 7DN, UK.
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