Audio Engineering Society

Chicago Section

Meeting Review, December 1998

other meeting reports 12/15/98 Meeting Highlights
by Bob Zurek

On Tuesday December 15th, Tim Coats the Business Development Manger of LMS North America gave a presentation entitled Numerical Acoustics for Transducer Development with Applications to Performance in Architectural Design. Tim began his presentation, with an overview of LMS' concepts for virtual prototype refinement. This system involves simulation, analysis, and refinement of vibro-acoustic systems within software. Tim then went on to define the bounds of the vibro-acoustic systems that LMS can work with. The first consideration in the process is transduction. The techniques developed by LMS are capable of simulating traditional loudspeakers which one would find in a home, car, or sound reinforcement audio systems; microloudspeakers such as those found in computers or phones; and chimes and buzzers, that one would find in automotive environments. The next considerations, deal with the frequency range of interest, and the size of the acoustic system. The final considerations deal with the bending wavelength of the system and the actuated media. Once all of these factors are weighed, one can then determine which method of acoustic simulation to use. The methods that Tim went into during the presentation were the Finite Element method (FEM), Boundary element method (BEM), Hybrid methods such as FBS, Statistical Energy Analysis (SEA), Load Path analysis (TPA), and Ray Tracing. Tim gave and overview of the LMS products that cover these areas such as SYSNOISE, RAYNOISE, VIOLINS, and MOZART. Tim discussed how these tools allow for prediction of acoustic performance in 3D porous materials as in the VIOLINS product, quick estimates of acoustic systems using SEA, coupled acoustic response using FEM and BEM, and prediction of high frequency response within complex enclosures using ray tracing. The combination of all of these tools along with multidiscipline analysis and optimization make up what LMS refers to as Virtual Prototype Refinement. Tim briefly discussed the multidiscipline analysis and optimization that is possible with LMS' LINK and OPTIMUS packages. After a lively discussion of the pros and cons of the various methods, Tim presented five examples of acoustic simulation problems that LMS typically deals with. The first example was a simplified model of a speaker in a box as would be found in a home loudspeaker. This example utilized a coupled Structural FEM to Acoustic BEM approach. The results of this analysis were directivity and pressure measurements. The second example explored the field of micro-transducers. In this example, a structural FEM, acoustic FEM, and IFEM approach was utilized. The model was meant to simulate a small electret microphone. The third and fouth examples utilized ray tracing methods to simulate the acoustic charateristics of a train station and a sports stadium. Reverberation time and speech transmission index were calculated from the analysis. The final example dealt with industrial noise control and used sensitivity analysis to improve the working conditions on a factory floor. Tim finished by summing up the need for acoustical analysis and virtual prototype refinement in product design.