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On the Propagation of Ultrasonic Waves of Finite Amplitude in Liquids
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1957
Year
Biomedical AcousticsEngineeringAcoustic FilterFluid MechanicsMechanical EngineeringFinite AmplitudeWave MotionAcoustic CavitationWave TheoryOcean AcousticsVibrationsPower UltrasoundPhysical AcousticUltrasonic Absorption CoefficientUltrasonic WavesSound PropagationInstrumentationAcoustic AnalysisAcoustic MethodsPhysicsUltrasonicsWave PropagationAcoustic PropagationExposimetryUltrasoundHarmonic IntensityApplied PhysicsAcoustic Tweezer
The study measured the ultrasonic absorption coefficient’s dependence on intensity in several liquids (water, ethyl and methyl ethers, toluene, transformer oil, glycerine) at 1.5 MHz using a thermal method (thermocouples) over 0.3–9 W cm⁻², and directly observed finite‑amplitude wave harmonics with quartz‑plate receivers, an acoustic filter to suppress standing waves, and a radiometer for absolute harmonic intensity. Absorption increased by almost two orders of magnitude, and measurements at static pressures up to 15 kg cm⁻² matched atmospheric‑pressure results within error, indicating a negligible cavitation effect.
The dependence of the ultrasonic absorption coefficient on the intensity was measured indifferent liquids (water, ethyl and methyl ethers, toluene, transformer oil, and glycerine) by means of the thermal method (thermocouples). The measurements were made at 1.5 Mc/sec with intensities of 0.3–9 w/cm2. There was found a considerable increase of nearly two orders of magnitude in the absorption. Measurement at higher static pressures, up to 15 kg/cm2, gives results which coincide, within the range of error, with the results of the measurements at atmospheric pressure, suggesting that the influence of cavitation is small. Direct experimental observation of the harmonics in a traveling wave of finite amplitude was accomplished. The receivers were quartz plates with their fundamental frequencies equal to the frequencies of the harmonics; to remove standing waves between the receiver and the transducer, an acoustic filter was used, consisting of a thin plate “transparent” for the appropriate harmonic and opaque for the fundamental at a certain angle. Absolute measurement of the harmonic intensity was obtained by a radiometer which was placed behind the acoustic filter.