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Parametric phase-delay estimation of sound transmitted through intact human lung
S Lu1, P C Doerschuk, G R Wodicka
1School of Electrical Engineering, Purdue University, West Lafayette, IN 47907-1285, USA.
Medical & Biological Engineering & Computing
|May 1, 1995
Summary
Respiratory sound transmission is frequency-dependent, with higher frequencies traveling faster to the chest wall than lower frequencies. This dispersion is likely due to variations in airway and lung tissue properties.
Area of Science:
- Respiratory acoustics
- Pulmonary physiology
Background:
- Understanding respiratory sound transmission is crucial for diagnosing lung conditions.
- Previous methods for analyzing sound propagation faced challenges with thoracic anti-resonances.
Purpose of the Study:
- To accurately estimate the phase delay of sound propagation from the trachea to the chest wall.
- To investigate the frequency-dependent characteristics of respiratory sound transmission.
Main Methods:
- Sonic noise (300-1600 Hz) was introduced into the mouths of 11 healthy adult males.
- Phase delay (tau(f)) was estimated using a linear parametric ARX statistical model.
- Non-parametric magnitude spectra guided the phase unwrapping process.
Main Results:
- Unambiguous and reliable phase delay estimates were obtained.
- A clear trend of decreasing phase delay with increasing frequency was observed.
- Higher frequency sounds reached the chest wall faster than lower frequency sounds.
Conclusions:
- Respiratory sound transmission is highly dispersive.
- This dispersion is likely caused by frequency-dependent wave speeds in the airways and lung parenchyma.
- The findings provide insights into the physical mechanisms of respiratory sound propagation.