Coherence-function relations between simultaneous measurements at three transducers are used and the power spectrum of the signal as received at each transducer is extracted from the flow-noise background using digital data processing. The method was first developed for on-board measurement of noise in moving vehicles, but it can be used also to reject other types of noise, such as instrument electronic noise. It is assumed that the flow noise at the three transducers is mutually uncorrelated, but this condition may not be satisfied if there is large-scale eddy formation in the flow. A multivariant random-process model is used to derive the coherence-function relations, and stationary random signals may be rejected as well as periodic signals. An experimental test is described using a loudspeaker as sound source. The power spectra were computed using a four-channel Fourier Analyser, and a 10-15 dB reduction in flow-noise interference was achieved. The extent of the noise rejection should be unlimited for ideal Gaussian noise. In the experiment the reduction was limited by the dynamic range of the analyser.
Rejection of flow noise using a coherence function method
Unterdrueckung des Stromgeraeusches mit Hilfe einer Kohaerenzfunktions-Methode
Journal of the Acoustical Society of America ; 62 , 2 ; 388-395
1977
8 Seiten, 5 Quellen
Article (Journal)
English
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