Acoustic Perturbation Measures Improve with Increasing Vocal Intensity in Individuals With and Without Voice Disorders.
M Brockmann-Bauser, J E Bohlender, D D Mehta
PMID 28528786WHAT IT FOUND
In women with and without voice disorders, jitter, shimmer, and HNR changed with loudness.
Louder voice lowered jitter and shimmer and raised HNR. Loudness affected these measures, and pathology did not consistently separate groups.
Key findings
01Loudness and voice SPL had a significant effect on jitter, shimmer, and HNR, and jitter and shimmer decreased while HNR increased as voice SPL increased.
02When loudness and voice SPL were considered, jitter, shimmer, and HNR did not significantly differ between patient and control groups or among diagnoses.
03Professional voice use level had significant differences in jitter, shimmer, and HNR when loudness was controlled.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
The sample was all women, so the findings may not apply to men. 60% of participants were Level I elite vocal performers, so voice training effects may be overrepresented. Only stable voice recordings were analyzed, and exclusions left unequal numbers of recordings across loudness levels and before and after treatment. Before and after comparisons involved only 33 patients and included either laryngeal surgery or voice therapy, so they cannot separate the effect of any single treatment. The matched-pair HNR difference was 1.2 dB, and the spread was 12.5 dB in controls and 19.1 dB in patients. This makes it difficult to use HNR alone for diagnosis.
The easy way to misread this
Do not conclude that jitter, shimmer, or HNR can diagnose voice disorders from this study. Louder voice changed these measures, jitter and shimmer did not separate patient and control groups, and the HNR difference was small with large spread.