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Entwicklung einer akustischen Kamera zur Lokalisation der drehzahlenabhängigen Geräusche von Antriebsstrangkomponenten

Authors Neugebauer, U.
Year 2011
Thesis Type Diploma thesis
Topic Audio Signal Processing
Keywords Aufnahmetechnik, technical acoustics, signal processing
Abstract Acoustic-metrology-related analysis of powertrain components requires in-depth testing on an appropriate test stand. In a majority of cases, acceleration sensors can be considered an appropriate tool for analysing structure-borne sound when researching into the acoustic characteristics of devices under test. However, specific recording of the share of noise emitted into the air requires employing specific microphone test arrays. This thesis aims at developing an opto-acoustic measurement system for localising noise emitting areas of powertrain components. Such systems are commonly referred to as ’acoustic camera’ and, in essence, consist of an optical camera system, a microphone array and a signal-processing unit for analysing data downstream (usually a software application). Visualisation of localised acoustic sources is achieved via semi-transparent overlap of optical imaging with calculated sound pressure mapping. The respective development task comprises both dimensioning, combination and prototyping of corresponding hardware as well as implementation of appropriate software modules. In order to achieve this, a 40-channel plane wheel array was designed to perform the scope of operations desired, in concert with a camera and a Delay&Sum Beamforming algorithm. Particular emphasis was put on rotation speed dependency of sound events occurring. In order to accommodate for such events, in addition to time-frequency analysis of measurement signals, the software allows for evaluation of occurring orders. Software implementation was entirely accomplished in MATLAB ® and allows easy handling and upgrading based on an integrated graphical user interface and modular software configuration. System performance evaluation is achieved by means of numerical simulations, via measurements under laboratory conditions, real-life test-stand application measurement of established and controllable sound source configurations, as well as reference point measurement of a select electric axle drive. This thesis was developed in cooperation with Magna Powertrain AG & Co KG in Lannach, Austria.
Supervisors Sontacchi, A., Ottowitz, L., Sigl, J.