Mechanical Design Solutions for Reducing Structure-Borne Vibrations in Microphones

Sammanfattning

Structure-borne vibrations can degrade microphone performance by introducing unwanted noise into the recorded audio signal. While vibration isolation principles are well established in larger mechanical systems, limited experimental work has been conducted on compact microphone assemblies. In particular, the influence of mounting geometry, elastic suspension and damping materials on vibration-induced disturbances remains insufficiently explored.This thesis investigates how mechanical design solutions affect structure-borne vibration transmission in compact microphone systems. Several concepts were designed, prototyped and experimentally evaluated under controlled laboratory conditions using analog microphone configurations. The concepts included variations in geometry, contact area, elastic suspension and damping materials. The recorded audio signals were analyzed using waveform inspection, RMS evaluation and frequency-domain analysis.The results demonstrate that the surrounding mechanical configuration strongly influences the recorded vibration response. Concepts based on elastic suspension and reduced rigid coupling generally achieved the greatest attenuation of the vibration-induced signal level recorded by the microphone. The final prototype, combining a circular microphone holder, two elastic bands and a 1 mm layer of Small-Cell CONFOR foam for local damping, reduced the RMS level by 14.78 dB relative to the reference configuration. This corresponds to an approximately 82% reduction in the vibration-induced signal magnitude relative to the reference level.The study demonstrates that compact mechanical isolation can substantially improve vibration robustness in microphone assemblies without relying on signal processing. The results further highlight the importance of the complete mechanical interface surrounding the microphone, where relatively small changes in geometry, stiffness and damping conditions can strongly influence vibration transmission.