Quantitative spectral evaluation of shimmer and jitter

Area of Science:

• Acoustic analysis of speech
• Voice disorders
• Signal processing

Background:

• Jitter and shimmer are acoustic measures of voice perturbation.
• Understanding their impact on speech acoustics is crucial for diagnosing voice disorders.
• Noise in speech signals can arise from harmonic amplitude variations.

Purpose of the Study:

• To investigate the acoustic impact of jitter and shimmer on synthesized speech.
• To determine the relationship between jitter, shimmer, and noise levels in speech spectra.
• To evaluate the clinical relevance of jitter and shimmer in differentiating functional voice disorders.

Main Methods:

• Synthesized speech waves were perturbed with controlled jitter and shimmer levels.
• Signal-to-noise ratio was calculated from speech wave spectra.
• Acoustic analysis of voices from 32 women with functional voice disorders was performed.

Main Results:

• Jitter introduced significantly higher noise levels compared to shimmer.
• Noise emerged at low frequencies and formant regions due to harmonic amplitudes.
• Jitter, not shimmer, was found to be relevant for differentiating hypo- and hyperfunctional voice disorders.
• Reduced jitter was observed in hyperfunctional voice disorders.

Conclusions:

• Jitter significantly contributes to noise in speech, particularly at lower frequencies and formant regions.
• Jitter is a key acoustic parameter for distinguishing between hypo- and hyperfunctional voice disorders.
• The reduction in jitter in hyperfunctional voice disorders may be linked to increased vocal fold tension.