Abstract
There are several methods available to determine Eigenmodes of structural objects. These can be calculated by modal analysis. The Eigenmodes cause maximum of displacements in the material at different positions. This effect is similar to a speaker. So the sound pressure is maximum at the points with maximal surface-velocity. With an acoustic camera these sound sources can be visualized with an appropriate signal processing method. A suitable algorithm is the statistically optimal near-field acoustical holography (SONAH). This algorithm shows its power at low frequencies in comparison to other (Beamforming) algorithms. Beamforming is a signal processing method to locate sound sources using an acoustic camera. In this chapter a comparison between the boundary element method (BEM) calculation and the SONAH sound processing method is performed. The BEM method is used to calculate the sound pressure field, which is caused by a vibrating surface of a structure. In a further step, a BEM software calculates with help of a structural harmonic analysis, which contains the displacement, velocity or acceleration of the elements, the sound pressure in the vicinity of the vibrating surface, especially on the surface. The harmonic analysis is given from a linear finite element method (FEM) software in this case. The measurement setup consists of a sawing blade with a diameter of 0.65 m and a thickness of about 0.005 m. In the middle, it is fixed by a clamping spigot. At a small drilled hole at the outer side, the sawing blade is connected to a shaker which impinges the sawing blade with different frequencies.
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Notes
- 1.
The characteristic is more weighted in this direction than in other directions.
- 2.
The software used to operate the acoustic camera.
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© 2012 Springer-Verlag Berlin Heidelberg
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Maier, C., Winkler, R., Pannert, W., Merkel, M. (2012). Comparison Between BEM Analysis and SONAH Measurements Using an Acoustic Camera. In: Öchsner, A., da Silva, L., Altenbach, H. (eds) Materials with Complex Behaviour II. Advanced Structured Materials, vol 16. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-22700-4_43
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DOI: https://doi.org/10.1007/978-3-642-22700-4_43
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