Deconvolution of azimuthal mode detection measurements

Pieter Sijtsma*, Harry Brouwer

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

7 Citations (Scopus)
14 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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