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Messung und Modellierung der akustischen Eigenschaften von Streckmetall

Authors Fuhs, S.
Year 2003
Thesis Type Diploma thesis
Topic Audio Signal Processing
Keywords Technische Akustik
Abstract In architecture expanded metal gratings are often used for encasing ceilings with ventilating systems behind. The mounting of the expanded metal gratings in large surfaces has a bearing on the room acoustics which can’t be disregarded. First ambition of this diploma thesis is to develop a simple and cost-effective measuring system for determining the octave absorption coefficients of expanded metal gratings. Because of the large hole-ratio and the three-dimensional structure of the expanded metal gratings, the absorption coefficients have to be determined in oblique incidence as well. The absorption coefficient is defined on the concept of insertion loss. The impulse response measurement is implemented with the swept-sine technique. With the insertion-loss method the measurement is carried out twice, with and without the expanded metal gratings on a rigid floor. After fading out the unwanted reflections by using the window- technique the results of the two measurements are related to each other. Furthermore several methods for eliminating the impulse response of the loudspeaker from the reflection of the specimen under test are discussed. The second part of this diploma thesis is to develop a MATLAB-application which simulates the measurement setup. These calculations are based on the wavefield theory, where the measuring error due to the finite dimension of the specimen and the affecting surrounding area is calculated.
Supervisors Höldrich, R.