Airborne noise characterisation of a complex machine using a dummy source approach

Abstract : The characterisation of vibrating sound sources is a challenge in noise and vibration engineering. In this thesis, an experimental approach to the characterisation of air-borne sound from a complex machine is investigated. A proper characterisation has to account for both radiation and diffraction phenomena in order to describe the sound source when inserted into an arbitrary space which enables prediction of sound pressure. A particular technique — a dummy source — has been conceived to deal with this problem. The dummy is a closed cabinet of similar size but much simpler shape than the complex machine, and it serves as a model of sound diffraction. The dummy is equipped with a flush-mounted array of loudspeaker drivers. The superposition of sound fields created by the individual drivers models sound radiation of the complex machine. This thesis introduces the concept of a dummy source and discusses three problems that need to be addressed for its practical application: (1) estimation of the transfer impedance of the space (the Green’s function), (2) the specification of the cabinet and the driver array, and (3) the estimation of the equivalent source strengths in terms of volume velocity. The approach is investigated via experimental and numerical case studies.
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Anders Sven Axel Lindberg. Airborne noise characterisation of a complex machine using a dummy source approach. Acoustics [physics.class-ph]. INSA de Lyon, 2015. English. ⟨NNT : 2015ISAL0082⟩. ⟨tel-01368596⟩

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