Using the full linearized Navier Stokes equations to numerically model losses comes at a high computational cost. This is especially the case in micro-acoustic devices such as hearing aids, condenser microphones and MEMS devices. The increasing interest in miniaturizing acoustic devices has made accurate and efficient models of acoustic viscous and thermal losses progressively more important. The results presented in this research assume that complete design and production freedom are available. The results show that a completely flat on-axis response is achievable even for very broad frequency ranges and that a reasonably flat response over a wide directivity can be obtained as well. The targeted frequency range is from 600 Hz up to 10 kHz and the range for the directivity is from 0 to 30. This is accomplished using a density and gradient-based optimization technique in conjunction with a fully coupled finite element model of the loudspeaker and the surrounding acoustic domain. The results are generated by optimizing the values and layout of stiffness, mass, and damping of both the speaker diaphragm and surround. Performance is investigated as the considered frequency range and off-axis requirements are progressively expanded. This paper demonstrates how significant improvement in frequency response and directivity of a loudspeaker may be obtained by optimizing the local properties of the materials for the diaphragm and surround.
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