Methods to characterize acoustic sources in flow ducts have been investigated. In the first part of this thesis a measurement procedure to characterize an air terminal device using an acoustic one-port source model based on the two microphone technique has been tested and validated. In order to provide a prediction of flow noise generation at different operating points for the device a scaling law was derived. Successful validation experiments were performed. In the second part a new method based on the multi-load technique was developed and used to characterise the source data of various piston-engines with non-linear behaviour. The source characterisation results were compared to results obtained using the well-known linear two-load technique. It was shown that the new non-linear multi-load technique gave improved results when the source was slightly non-linear. In the third part an improved method to characterize noise sources in high temperature flowducts has been suggested. As a test environment for the standard two microphone technique a helium-air mixture has been used to simulate acoustical conditions similar to hot exhaust gas systems. In order to test the method the passive acoustic properties of automotive diesel engine and an unflanged flow duct termination have been experimentally determined. The experimental results for duct termination have been compared to theoretical predictions. Keywords: Acoustic source, one–port, source model, duct termination, source impedance, reflection coefficient, source strength, IC-engine, flow duct, multi-load method, non-linear / QC 20120208
| Identifer | oai:union.ndltd.org:UPSALLA1/oai:DiVA.org:kth-77701 |
| Date | January 2005 |
| Creators | Rämmal, Hans |
| Publisher | KTH, MWL Marcus Wallenberg Laboratoriet, Stockholm |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Licentiate thesis, comprehensive summary, info:eu-repo/semantics/masterThesis, text |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess |
| Relation | Trita-AVE, 1651-7660 ; 2005:38 |
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