Inverse Numerical Acoustics (INA) is the process by which the measurements of the sound pressure near a vibrating object, such as an engine, can be used to reconstruct the surface velocities of the object. This is required when it is difficult to conduct measurement on the structure or when the full structural FE model is not available. In such scenarios, the INA technique allows to back calculate the operational vibrations based on operational near field pressure measurements. When the surface velocities of a vibrating object are known which are independent of the boundary conditions, then the object can be used as a source in any application to compute the sound pressure levels in the surrounding (far field). This paper describes an experimental procedure that relies on INA to characterize an engine noise source in this manner. To this end, a robotic manipulator first measured sound pressures at multiple points in the near acoustic field. This process resulted in an accurate mapping of the measured data onto the analysis model. INA analysis was then performed to reconstruct the surface velocities. Next, a validation of far field sound pressure levels at 1m away from the engine was carried out by performing forward acoustic analysis with the computed surface velocities as the source input. As a result, the reconstructed sound pressure levels show a good level of correlation with the test. This methodology can be used for integrating the engine as a noise source in various applications.
Engine Sound Source Characterization Based on Inverse Numerical Acoustics
Sae Technical Papers
Noise and Vibration Conference & Exhibition ; 2021
2021-08-31
Aufsatz (Konferenz)
Englisch
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