摘要:

This investigation concerns free linear gas bubble oscillations in liquids. Of prime interest is the eigenfrequency, and in particular its real part, here named as the transient frequency. The conceptual difference between the more frequently consulted resonance frequency and the transient frequency is first addressed by means of the classical mechanical oscillator. Next, bubble pulsations in liquids are discussed and an existing model is used for the gas–liquid interaction from which an approximate expression for the eigenfrequency is derived. A rationale for the approximate evaluation of the functions modeling the thermal processes is suggested which is independent of the frequency content of any possible pressure excitation. Moreover, compressibility effects are not approximated in the derivation presented here. The quantitative difference between the adiabatic resonance frequency and the derived estimate of the transient frequency is found to be of significance for small bubbles. Finally, the similarity between a standard mechanical oscillator and a bubble in a liquid for the case of liquid-compressibility effects only is discussed.

ISSN:0001-4966    

DOI:10.1121/1.420113

出版商:Acoustical Society of America    

年代:1997

数据来源: AIP

摘要:

Members of our group have previously demonstrated that TV holography may be used to measure the amplitude and the phase distributions of a sound field in air. This technique is not limited to acoustic fields in air, but may be applied to acoustic fields in any transparent medium. Its applicability to ultrasonic fields in water is demonstrated in this Letter.

ISSN:0001-4966    

DOI:10.1121/1.420114

出版商:Acoustical Society of America    

年代:1997

数据来源: AIP

摘要:

Masked thresholds were measured for five subjects in an anechoic chamber. The signal (a 500-Hz tone, an 8000-Hz tone, or a broadband noise) was presented from a movable loudspeaker located in the horizontal plane at ear level. A continuous noise masker came from two fixed loudspeakers at±14°azimuth. In different threshold runs the signal was either stationary (positioned at 0° or at 15° azimuth), or it moved during its on-time (at a velocity of 30°/s or 90°/s) through an arc from−15°to+15°.There was no evidence that any of the moving signals was more detectable than a stationary signal when threshold variation due to position changes of the stationary signal was taken into account. Likewise, there was no evidence that signal velocity affected detectability when signal duration was taken into account. These results agree with previous reports obtained with simulated moving signals presented via earphones and suggest that if horizontal motion-sensitive mechanisms exist in the auditory system, such mechanisms do not contribute to signal detectability.

ISSN:0001-4966    

DOI:10.1121/1.421013

出版商:Acoustical Society of America    

年代:1997

数据来源: AIP