Volume 126, Issue 5, November 2009
Index of content:
- TRANSDUCTION 
126(2009); http://dx.doi.org/10.1121/1.3216911View Description Hide Description
A broadband cluster transducer, based on barrel-stave flextensional transducer technology, was designed, built, and tested in air and seawater at Defence R&D Canada—Atlantic. The design goal was to develop a transducer that exhibited a transmitting voltage response of greater than from 1 to 7 kHz and have the potential for beamsteering. Six orthogonal piezoceramic-driven class I barrel-stave transducer elements mounted on a central manifold were wired separately, allowing each to be driven individually or in combination with the other elements. The resonance modes under the following drive conditions were determined from in-air conductance measurements: each of the six elements excited individually as mass-loaded class I flextensionals, three collinear pairs driven separately as class III flextensionals, and all six elements driven in phase simultaneously. The fully-driven cluster was found to have a transmitting voltage response of greater than from 800 Hz to more than 10 kHz and its topology is amenable to beamsteering that is yet to be characterized.
126(2009); http://dx.doi.org/10.1121/1.3212943View Description Hide Description
The orthotropic model of the plate is established and the genetic simulated annealing algorithm is developed for optimization of the mode distribution of the orthotropic plate. The experiment results indicate that the orthotropic model can simulate the real plate better. And optimization aimed at the equal distribution of the modes in the orthotropic model is made to improve the corresponding sound pressure responses.
126(2009); http://dx.doi.org/10.1121/1.3212917View Description Hide Description
Simple analytical expressions of mechanical resistance, such as those formulated by Škvor/Starr, are widely used to describe the mechanical-thermal noise performance of a condensermicrophone. However, the Škvor/Starr approach does not consider the location effect of acoustic holes in the backplate and overestimates the total equivalent mechanical resistance and mechanical-thermal noise. In this paper, a modified form of the Škvor/Starr approach is proposed to address this hole location dependent effect. A mode shape factor, which consists of the zero order Bessel and modified Bessel functions, is included in Škvor’s mechanical resistance formulation to consider the effect of the hole location in the backplate. With reference to two B&K microphones, the theoretical results of the -weighted mechanical-thermal noise obtained by the modified Škvor/Starr approach are in good agreements with those reported experimental ones.