Impedance tube testing to measure acoustical properties of noise absorbing materials
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Abstract
Noise is a major concern across engineering disciplines. In aerospace engineering, sound absorbing materials are used to reduce noise in airplane cabins. The sound absorption coefficient is a measure of a material's ability to absorb sound at a given frequency. This is traditionally measured with an impedance tube where sound is emitted through a tube into a material, then two microphones measure how much sound was absorbed and reflected by the material. The goal of this project was to use this method to determine the sound absorption coefficients of fiberglass, three types of foam, and a 3D printed absorber across low, medium and high frequency ranges. The 3D printed structure had higher absorption in the low frequency range compared to the traditional insulators, while the foams and fiberglass had better broadband absorption across frequencies. The measurements were validated against previous data from our lab. My current and future work involves investigating other 3D printed geometries to achieve improved acoustical properties compared to traditional materials.
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Research project completed at the Department of Aerospace Engineering.