Detecting inaudible vocal organ changes through glottal inverse filtering.

The aim of this study was to investigate if there were objective quantities extracted from the speech pressure waveforms that underlay inaudible changes in the symptoms of the vocal organ. This was done through analyzing 180 voice samples obtained from nine subjects (five females and four males) before and after exposure to a placebo substance (lactose) and an organic dust substance. Acoustical analysis of the voice samples was achieved by using glottal inverse filtering. Results showed that the values of primary open quotient and primary speed quotient changed significantly (P<0.05) as did the amplitude quotient (P<0.01). Exposure to lactose resulted in significant changes of secondary open quotient (P<0.05) but opposite to effects found for exposure to organic dust. Modeling of the vocal tract into cross-sectional planes revealed that the immediate plane above the vocal folds correlates inversely with the feeling that voice is tense, or feeling the need to make an effort when speaking in addition having a feeling of shortness of breath or the need to gasp for air. Such results may point to acoustically detected subclinical changes in the vocal organ that the subject him/herself feels while they remain perceptually undetected by others.

Pilot study on acute voice and throat symptoms related to exposure to organic dust: preliminary findings from a provocation test.

The aim of this pilot research was to investigate acute voice and throat symptoms related to organic dust exposure among nine subjects with suspected occupational rhinitis or asthma. Subjective voice and throat symptoms were recorded before and after an occupational exposure test. In addition, the study included perceptual assessment of subjects' voice samples recorded before and after the exposure tests. The results showed a number of (statistically) significant voice and throat changes in symptoms based on subjects' own assessments. These symptoms included a hoarse, husky, or tense voice, requiring an extra effort when speaking and difficulty in starting phonation (P < 0.05). Other significant symptoms included feeling of shortness of breath or the need to gasp for air and feeling that the voice is weak or that it does not resonate (P < 0.01). Such changes were not, however, detected by voice clinicians in the listening test of subjects' voice samples recorded before and after the exposure. These results suggest that the larynx reacts to organic dust with symptoms that are felt by the patient rather than heard by the voice clinician. The voice disorder in such cases is a diagnosis based on symptoms expressed by subjects.