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Abstract
This thesis describes the development of a numerical model of the propagation of sound waves in fluids with viscous and thermal losses, with application to the simulation of acoustic transducers, in particular condenser microphones for measurement. The theoretical basis is presented, numerical tools and implementation techniques are described and performance tests are carried out.
The equations that govern the motion of fluids with losses and the corresponding boundary conditions are reduced to a form that is tractable for the Boundary Element Method (BEM) by adopting some hypotheses that are allowable in this case: linear variations, absence of flow, harmonic time variation, thermodynamical equilibrium and physical dimensions much larger than the molecular mean free path.
A formulation of the BEM is also developed with an improvement designed to cope with the numerical difficulty associated with very close surfaces, as found in condenser microphones, where the membrane has a backplate very close behind. This improvement could be useful for many other problems where the BEM is applied.
The numerical implementation that includes both viscous and thermal effects is then worked out. Some numerical manipulations are developed to satisfy the more complicated boundary conditions, and a model of a condenser microphone with a coupled membrane is developed. The model is tested against measurements of ¼ inch condenser microphones and analytical calculations. A detailed discussion of the results is given.
The equations that govern the motion of fluids with losses and the corresponding boundary conditions are reduced to a form that is tractable for the Boundary Element Method (BEM) by adopting some hypotheses that are allowable in this case: linear variations, absence of flow, harmonic time variation, thermodynamical equilibrium and physical dimensions much larger than the molecular mean free path.
A formulation of the BEM is also developed with an improvement designed to cope with the numerical difficulty associated with very close surfaces, as found in condenser microphones, where the membrane has a backplate very close behind. This improvement could be useful for many other problems where the BEM is applied.
The numerical implementation that includes both viscous and thermal effects is then worked out. Some numerical manipulations are developed to satisfy the more complicated boundary conditions, and a model of a condenser microphone with a coupled membrane is developed. The model is tested against measurements of ¼ inch condenser microphones and analytical calculations. A detailed discussion of the results is given.
Original language  English 

Place of Publication  Lyngby, Denmark 

Publisher  Technical University of Denmark 
Number of pages  181 
ISBN (Print)  8791184096 
Publication status  Published  Jun 2002 
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 1 Finished

Numerical Transducer Modelling
Cutanda Henriquez, V., Jacobsen, F., Tarnow, V., Hamdi, M. A. & Gramtorp, J.
01/09/1998 → 17/06/2002
Project: PhD