PubMed · 6052079
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B B Bauer, A J Rosenheck, L A Abbagnaro. 1967. External-ear replica for acoustical testing.. https://doi.org/10.1121/1.1910553
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Sonic noise between 300 and 1600 Hz is introduced into the mouths of 11 healthy adult male subjects at resting lung volume and is detected over the anterior extrathoracic trachea and at three sites on the right posterior chest wall. To overcome the difficulties associated with non-parametric phase unwrapping due to thoracic anti-resonances, the phase delay tau(f) of propagation between the trachea and the chest wall is estimated using a linear parametric ARX-type statistical model with the non-parametric magnitude spectra as a guide. The resulting tau(f) estimates are unambiguous and reliable, and show a clear trend of decreasing tau(f) with increasing frequency, indicating that sound at higher frequencies reaches the chest wall faster than that at lower frequencies. This finding indicates that respiratory sound transmission is highly dispersive, most probably owing to frequency-dependent airway and parenchymal wavespeeds.
A parametric phase delay estimation technique is used to determine the spatial and inhaled gas composition dependencies of sound propagation time through an intact human lung at frequencies of 150-1200 Hz. Noise transmission measurements from the mouth to the extrathoracic trachea and six sites on the posterior chest wall are performed in 11 healthy adult subjects at resting lung volume after equilibration with air, an 80% helium-20% oxygen mixture, and an 80% sulfurhexafluoride-20% oxygen mixture. The phase delay, tau(f), exhibits a bilateral asymmetry with relatively decreased delays to the left posterior chest as compared with the right. The phase delay to lower lung sites is greater than to upper sites at frequencies below 300 Hz; yet the opposite is found at higher frequencies, indicating changing propagation pathways with frequency. There is no measurable effect of inhaled gas composition on tau(f) below 300 Hz. At higher frequencies, changes in tau(f) that reflect the relative sound speed of the particular inhaled gas are observed. These findings support and extend previous measurements and hypotheses concerning the strong frequency dependence of the acoustical properties of the intact respiratory system.
Authors present the analysis of the voice in 88 normal subjects and 159 dysphonic patients by simultaneously measurements of Jitter (acoustical short-term indicator of aperiodicity) and "Glottal Leakage" (aerodynamic parameter calculated by the ratio of Oral Airflow and Intensity). All the measurements were performed, with EVA apparatus, on the most stable part of a steady-state vowel /a/. The reference method was the rating by a jury along a global perceptual scale. Statistical tests confirm that Jitter and "Glottal Leakage" are relevant to evaluate the quality of the voice. Discriminant analysis allows to find out a fairly-good rate of discrimination of 63.1% (Randomly rating would have been 25%) The authors conclude on the interest of such a protocol and present suggestions to improve it by taking in count phénomena during the vocal attack and middle-term variations.