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On the sound field from a moving source in a viscous medium
1Marine Physical Laboratory, Scripps Institution of Oceanography, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0238, USA. mjb@mpl.ucsd.edu
The Journal of the Acoustical Society of America
|January 13, 2004
Summary
A moving sound source in a viscous medium creates distinct waves. Sound waves are attenuated and frequency-shifted, with higher attenuation when the source approaches the receiver.
Area of Science:
- Acoustics
- Fluid Dynamics
- Wave Propagation
Background:
- Understanding sound propagation in dissipative media is crucial for acoustics.
- The behavior of sound waves from moving sources is complex, especially in viscous environments.
Purpose of the Study:
- To develop a wave-theoretic model for sound fields generated by a moving harmonic source in a viscous medium.
- To analyze the characteristics of propagating and evanescent waves, including frequency and attenuation.
Main Methods:
- A one-dimensional model was used for wave-theoretic analysis.
- Formulated expressions for frequency and attenuation coefficients of different wave types.
Main Results:
- Identified inbound and outbound propagating waves with Doppler frequency shifts.
- Observed an evanescent wave upon source passage, highly attenuated and dependent on motion and dissipation.
- Attenuation scales with the square of frequency, characteristic of viscous dissipation.
- Significant asymmetry in attenuation was found, with higher attenuation during approach.
Conclusions:
- The study provides a detailed analysis of sound fields from moving sources in viscous media.
- Viscous dissipation leads to frequency-dependent and asymmetrical attenuation.
- The Mach number significantly influences the attenuation asymmetry.