Volume 117, Issue 1, January 2005
Index of content:
- ULTRASONICS, QUANTUM ACOUSTICS, AND PHYSICAL EFFECTS OF SOUND 
Fine-tuning molecular acoustic models: sensitivity of the predicted attenuation to the Lennard–Jones parameters117(2005); http://dx.doi.org/10.1121/1.1828547View Description Hide Description
In a previous paper [Y. Dain and R. M. Lueptow, J. Acoust. Soc. Am. 109, 1955 (2001)], a model of acoustic attenuation due to vibration-translation and vibration-vibration relaxation in multiple polyatomic gas mixtures was developed. In this paper, the model is improved by treating binary molecular collisions via fully pairwise vibrational transition probabilities. The sensitivity of the model to small variations in the Lennard–Jones parameters—collision diameter (σ) and potential depth (ε)—is investigated for nitrogen-water-methane mixtures. For a test mixture, the transition probabilities and acoustic absorption curves are much more sensitive to σ than they are to ε. Additionally, when the 1% methane is replaced by nitrogen, the resulting mixture becomes considerably more sensitive to changes of The current model minimizes the underprediction of the acoustic absorption peak magnitudes reported by S. G. Ejakov et al. [J. Acoust. Soc. Am. 113, 1871 (2003)].
117(2005); http://dx.doi.org/10.1121/1.1828500View Description Hide Description
The electroacoustic efficiency of high-power actuators used in thermoacoustic coolers may be estimated using a linear model involving a combination of six parameters. A method to identify these equivalent driver parameters from measured total electrical impedance and velocity-voltage transfer function data was developed. A commercially available, moving-magnet driver coupled to a functional thermoacoustic cooler was used to demonstrate the procedure experimentally. The method, based on linear electrical circuit theory, allowed for the possible frequency and amplitude dependence of the driver parameters to be estimated. The results demonstrated that driver parameters measuredin vacuo using this method can be used to predict the driver efficiency and performance for operating conditions which may be encountered under load.
117(2005); http://dx.doi.org/10.1121/1.1828675View Description Hide Description
This paper deals with the reflection of a two-dimensional harmonic Lamb wave at the beveled end of a plate. The existence of a resonant edge mode is described by a numerical model. It is proved that the edge mode is the resonance of different complex modes. The behavior of this mode as a function of the bevel angle is studied. Its amplitude decreases and its resonance frequency shifts as the bevel angle decreases from 90 to 85 deg. An unexpected strong variation of the repartition of the reflected energy is linked to this phenomenon.