The determination of acoustic reflection coefficients by using cepstral techniques, II: Extensions of the technique and considerations of accuracy

1986 ◽  
Vol 110 (2) ◽  
pp. 203-222 ◽  
Author(s):  
J.S. Bolton ◽  
E. Gold
Keyword(s):  
Reflection Coefficients ◽  
Acoustic Reflection

Nasal airway geometry: comparison between acoustic reflections and magnetic resonance scanning

1993 ◽  
Vol 75 (6) ◽  
pp. 2811-2819 ◽  
Author(s):  
O. Hilberg ◽  
F. T. Jensen ◽  
O. F. Pedersen
Keyword(s):  
Magnetic Resonance ◽  
Nasal Cavity ◽  
Posterior Part ◽  
Interindividual Variation ◽  
Acoustic Measurements ◽  
Cross Sectional ◽  
Acoustic Reflection ◽  
Magnetic Resonance Imaging Mri ◽  
Magnetic Resonance Scanning

To evaluate the accuracy of the acoustic reflection (AR) technique for determination of nasal cavity cross-sectional areas, the area-distance function of both sides of the nose was determined in 10 subjects and compared with magnetic resonance imaging (MRI). Interindividual variation for the correlation between MRI and AR was seen, but in general the areas from 1 to 6 cm into the nasal cavity measured by AR were larger than areas measured by MRI, especially where the surface was most convoluted. The total volume for this region was 6.47 +/- 1.83 (SD) cm3 for AR and 5.65 +/- 1.34 cm3 for MRI. It was demonstrated that this could be due to errors in calculation of the areas on the basis of MRI and AR. In the posterior part of the nasal cavity and the epipharynx, there was a convincingly higher correlation between acoustic measurements and a scan perpendicular to the assumed geometrical axis of the epipharynx than between acoustic measurements and coronal scanning. This indicates that the sound axis roughly follows the geometrical axis. In a model of two tubes (nasal cavities) joined in a larger tube (the epipharynx), closure of the posterior part of the latter revealed that the contralateral nasal cavity is likely to cause overestimation of the posterior part of the epipharynx during AR compared with MRI.

On: “Special Report of the Subcommittee on Polarity Standards” by Ben B. Thigpen, A. E. Dalby, and Ralph Landrum (GEOPHYSICS, August 1975, p. 694–699)

Geophysics ◽  
1976 ◽  
Vol 41 (2) ◽  
pp. 324-324
Author(s):  
W. T. Valenta
Keyword(s):  
Reflection Coefficient ◽  
Compressional Wave ◽  
Velocity Versus ◽  
Reflection Coefficients ◽  
Special Report ◽  
Sonic Logs ◽  
The Relationship

In their report, the authors recommend that the arrival of a compressional wave at a geophone or hydrophone shall ultimately produce a trough (downward or leftward kick) on a seismogram; but they don’t say why. On sonic logs and displays of velocity versus time, velocity increases are up; likewise for density increases on density logs; likewise for positive reflection coefficients on reflection coefficient logs computed from the previously mentioned logs. Should not seismograms, which ideally are bandlimited reflection coefficient logs, conform to the same convention? The committee succeeded in the objectives of establishing the relationship between impulse‐source systems and vibratory‐source systems and of establishing tests for the determination of the polarity of a given system. I feel strongly that the committee should recommend that a compressional arrival shall produce a peak on a seismogram.

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