Deconvolution of azimuthal mode detection measurements

Pieter Sijtsma, Harry Brouwer

Research output: Contribution to journalArticleScientificpeer-review

5 Citations (Scopus)
8 Downloads (Pure)

Abstract

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.

Original languageEnglish
Pages (from-to)1-14
Number of pages14
JournalJournal of Sound and Vibration
Volume422
DOIs
Publication statusPublished - 26 May 2018

Keywords

  • Acoustic beamforming
  • Azimuthal mode detection
  • Deconvolution
  • Non-equally spaced array

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