gms | German Medical Science

Dreiländertagung D-A-CH
24. Wissenschaftliche Jahrestagung der Deutschen Gesellschaft für Phoniatrie und Pädaudiologie e. V.

Deutsche Gesellschaft für Phoniatrie und Pädaudiologie e. V.

28. - 30.09.2007, Innsbruck, Österreich

Voice Loudness and Gender Effects on Jitter and Shimmer in Healthy Adults

Der Einfluss von Stimmlautstärke und Geschlecht auf Jitter und Shimmer bei stimmgesunden Erwachsenen


  • corresponding author presenting/speaker Meike Brockmann - Department of Speech Pathology, Clinic of Otorhinolaryngology, Head and Neck Surgery, Univ. Hosp. Zurich, Zurich, Switzerland
  • author Claudio Storck - Department of Phoniatrics, Clinic of Otorhinolaryngology, Head and Neck Surgery, Univ. Hospital Basel, Basel, Switzerland
  • author Paul N. Carding - Department of Speech, Voice and Swallowing, Otolaryngology, Freeman Hospital, Newcastle upon Tyne, United Kingdom
  • author Michael J. Drinnan - Medical Physics Department, Freeman Hospital, Newcastle upon Tyne, United Kingdom

Deutsche Gesellschaft für Phoniatrie und Pädaudiologie. Sektion Phoniatrie der Österreichischen Gesellschaft für HNO-Heilkunde, Kopf- und Halschirugie. Schweizerische Gesellschaft für Phoniatrie. Dreiländertagung D-A-CH, 24. Wissenschaftliche Jahrestagung der Deutschen Gesellschaft für Phoniatrie und Pädaudiologie e.V.. Innsbruck, Österreich, 28.-30.09.2007. Düsseldorf: German Medical Science GMS Publishing House; 2007. Doc07dgppV04

The electronic version of this article is the complete one and can be found online at:

Published: August 28, 2007

© 2007 Brockmann et al.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( You are free: to Share – to copy, distribute and transmit the work, provided the original author and source are credited.


The main 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. Fifty-seven healthy adults (1:1 f:m) aged 20 to 40 years were included in this cross-sectional single cohort study. Three phonations of /a/ at “soft”, “medium” and “loud” individual voice 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.

Shimmer and jitter significantly increased with decreasing voice loudness especially in phonations below 75dB and 80dB respectively (Figure 1 [Fig. 1], Figure 2 [Fig. 2]). In soft and medium phonation, males were generally louder and showed significantly less shimmer. However, men had higher jitter when phonating softly. Gender differences in shimmer and jitter at medium loudness appeared to be mainly linked to different habitual voice loudness levels in women and men (Figure 1 [Fig. 1], Figure 2 [Fig. 2]). This pragmatic study shows significant voice loudness and gender effects on perturbation. In clinical assessment, requesting phonations above 80dB, 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 voice loudness is requested, should be further investigated.



This study aims to examine voice intensity and gender effects on jitter and shimmer in vowel phonation in healthy adults between 20-40 years. Furthermore, implications for acoustic voice assessment are discussed.

Jitter and shimmer, objective acoustic voice analysis parameters, are routinely measured in voice assessment as recommended by international research associations [1], [2]. Jitter describes Fundamental Frequency (F0) variability and shimmer voice Sound Pressure Level (SPL) variability from one acoustic cycle to the next. Since acoustic waves correlate with vocal fold vibration, both parameters indirectly assess vibratory properties, and therefore physiological and pathological characteristics of voice.

In clinical and research settings, jitter and shimmer are widely used to evaluate outcomes following voice therapy or voice surgery, to compare intervention types and to describe voice characteristics of specific vocal groups (such as singers or children). Despite frequent application, jitter and shimmer reliability, sensitivity and specificity are presently unsatisfactory [3], [4]. Especially the impact of different voice intensity levels or gender on jitter and shimmer have been inconsistently and contradictorily described. The lack of control for these factors might result in misleading assessment outcome which may consequently negatively affect the diagnostic value of this assessment type.


70 healthy volunteers between 20 and 40 years were recruited to this cross-sectional single cohort study. Exclusion criteria were (a) a hoarse voice on the day of recording (b) a voice disorder history (c) reported medication or diseases affecting voice function (d) reported formal individual voice training or therapy (e) a tumor or surgery in the torso, head and neck region in the last 18 months (f) an intubation in the last 18 months (g) the inability to phonate 5 seconds of /a/. Voice recordings were not used, if the mean GRBAS scale score [5], rated by two independent experts on the basis of three phonations, was 1 or higher.

A total of 57 participants, 28 women aged from 20 to 39 years (mean: 28.8 years), and 29 men from 20 to 39 years (mean: 28.1 years), were included for acoustic voice analysis. Each subject provided 9 phonations, giving a total of 513 individual phonations for analysis. Of all 70 recruited participants, 12 with a mean GRBAS score of >1 in one voice characteristic, and one person unable to phonate for 5 seconds were excluded.


Participants were recorded in a sound-proof room, using a head-mounted off-axis positioned microphone with 10cm microphone-mouth distance, and a portable DAT recorder. Recordings were converted to digital sound files (WAV format) with a sampling rate of 48000 Hz and 32-bit resolution. Acoustic analysis was conducted with Praat [6] using second 0.5 to 3.5 from voice onset. Perturbation parameters were “Jitter %” and “Shimmer dB”.

During a training phase of ten minutes maximum, participants were asked to “sustain /a/ for 5 seconds at normal pitch and habitual loudness”. Then they were asked to phonate “as loud as possible” and “as soft as possible”. When participants could produce three distinguishable loudness levels, five seconds of /a/, at each loudness level, repeated 3 times in randomised order, were recorded. After acoustic analysis, phonation level (soft/medium/loud) and gender (f/w) effects on voice SPL, F0, jitter and shimmer were assessed using descriptive and inferential statistics (ANOVA).


The differences between phonation levels (soft/medium/loud) were significant (p<0.05) for SPL, F0, shimmer and jitter. Shimmer and jitter significantly increased with decreasing voice amplitude (Figure 1 [Fig. 1], Figure 2 [Fig. 2]). Considerably higher shimmer and jitter variability was observed below 75 and 80dB in both genders.

Men had significantly smaller mean shimmer when asked to produce soft and medium phonations. However, Figure 1 [Fig. 1], which illustrates actual voice SPL distribution and not phonation levels, shows no obvious gender effect at medium Sound Pressure Levels. Men had higher mean jitter in soft phonation. But in medium and loud phonation jitter was similar between genders.


This pragmatic study modelling a typical clinical task provides baseline data for the effects of voice loudness and gender on acoustic voice parameters in healthy young adults between 20 and 40 years. Both jitter and shimmer increase dramatically as SPL decreases especially between “medium” to “soft” individual voice intensity. Below 80dB and 75dB respectively, small SPL variations lead to large changes in jitter and shimmer. These low SPL intensities are likely associated with small intrinsic vocal fold tension and vibration amplitudes, potentially causing more mucosa movement variability, and resulting in higher perturbation.

The levels of shimmer and jitter appeared comparable between men and women at any given SPL (Figures 1 [Fig. 1], Figure 2 [Fig. 2]). However, in a pragmatic clinical situation, when asked for “comfortable” voice loudness, women tend to phonate quieter, and so may appear more pathologic. So gender differences at normal voice loudness may be mainly linked to different habitual voice intensities between women and men. This effect was particularly evident in shimmer measurements. For this reason normative values can not be simply transferred between genders.

Problematic in clinical practice is, that “normal” or “comfortable” voice loudness is normally below 75 dB [7]. In our work, women and men produced voice below 75dB and 80dB respectively in “medium” phonation. Therefore, SPL control could be used to enhance voice assessment reliability, for example by requesting phonations above 80dB. However, it is unclear how jitter and shimmer respond to SPL control, or how SPL effects perturbation in disordered voices or other age groups. These questions have to be addressed in further research to ensure jitter and shimmer measurement reliability.


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