Deconvolution of azimuthal mode detection measurements

Deconvolution of azimuthal mode detection measurements

Sijtsma, P. (TU Delft Aircraft Noise and Climate Effects; PSA3: Pieter Sijtsma Advanced AeroAcoustics)
Brouwer, Harry (Royal Netherlands Aerospace Centre NLR)

2018-05-26

Unequally spaced transducer rings make it possible to extend the range of detectable azimuthal modes. The disadvantage is that the response of the mode detection algorithm to a single mode is distributed over all detectable modes, similarly to the Point Spread Function of Conventional Beamforming with microphone arrays. With multiple modes the response patterns interfere, leading to a relatively high “noise floor” of spurious modes in the detected mode spectrum, in other words, to a low dynamic range. In this paper a deconvolution strategy is proposed for increasing this dynamic range. It starts with separating the measured sound into shaft tones and broadband noise. For broadband noise modes, a standard Non-Negative Least Squares solver appeared to be a perfect deconvolution tool. For shaft tones a Matching Pursuit approach is proposed, taking advantage of the sparsity of dominant modes. The deconvolution methods were applied to mode detection measurements in a fan rig. An increase in dynamic range of typically 10–15 dB was found.

Acoustic beamforming
Azimuthal mode detection
Deconvolution
Non-equally spaced array

http://resolver.tudelft.nl/uuid:ce77a3b5-11dc-47d9-a116-4c058d9a5b45

https://doi.org/10.1016/j.jsv.2018.02.029

2020-02-22

0022-460X

Journal of Sound and Vibration, 422, 1-14

Institutional Repository

journal article

© 2018 P. Sijtsma, Harry Brouwer