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An inverse analytical method for extracting liner impedance from pressure measurements
KTH, Superseded Departments, Aeronautical and Vehicle Engineering.
KTH, Superseded Departments, Aeronautical and Vehicle Engineering.ORCID iD: 0000-0002-8474-8563
2004 (English)In: Collection of Technical Papers: 10th AIAA/CEAS Aeroacoustics Conference, 2004, Vol. 1, 434-450 p.Conference paper (Refereed)
Abstract [en]

The in-situ method has been used for a long time as an easy, quick and direct method for measuring the acoustic impedance of locally reacting liners with and without flow. Several drawbacks and problems have been reported with the use of this method, which motivated the development of indirect methods to deduce the impedance from the measurement of the pressure field. A new inverse analytical technique is presented in this paper. The liner sample is placed inside a rectangular duct. The amplitude of the plane wave incident towards the lined section is measured using the two-microphone technique. The reflection coefficient at the exit plane is also measured using the same technique. These measured values are fed to an analytical model for sound propagation through the lined section, which is constructed using mode-matching. A minimization scheme is used to find the liner impedance value in the complex plane to match the calculated sound field to the measured one at the microphone positions already used for the two microphone measurements. The results show that the proposed technique can educe or measure the impedance to an acceptable accuracy.

Place, publisher, year, edition, pages
2004. Vol. 1, 434-450 p.
Keyword [en]
Acoustic fields, Acoustic impedance, Aircraft engines, Algorithms, Ducts, Mathematical models, Microphones, Optimization, Pressure measurement, Acoustic materials, Impedance measurements, Inverse analytical method, Liner impedance, Aviation
National Category
Engineering and Technology
URN: urn:nbn:se:kth:diva-61822ScopusID: 2-s2.0-19644393098ISBN: 1563477130OAI: diva2:479704
Collection of Technical Papers - 10th AIAA/CEAS Aeroacoustics Conference. Manchester- 10 May 2004 - 12 May 2004

QC 20120125

Available from: 2012-01-18 Created: 2012-01-18 Last updated: 2016-09-02Bibliographically approved

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