V.V.Krizhanovskii, V.V.Krizhanovskii (jr.) Estimating the efficiency of inhomogeneity detection in a wall of a piecewise-homogeneous cylinder |
Acoustic bulletin, Vol. 8 ¹ 1-2, (2005) |
| The paper deals with efficiency of detecting of acoustic inhomogeneity layer in the wall of a piecewise-homogeneous finite cylinder from the field excited by the incoherent axisymmetric source on an internal surface of the cylinder and recorded by the sensors on its external wall. The informative parameters of layer inhomogeneity are its width and density, propagation velocity of longitudinal acoustic vibration and their attenuation. A statistical problem of detecting a signal from discontinuity layer on a background of uncorrelated interference is formulated for vibrational velocity field recorded on the external wall of the layered cylinder. A cross power spectral density of the acoustic field in the given set of receiving points spatially distributed on the cylinder's surface is used as the informative statistical parameter. The detection efficiency is estimated by the Neumann-Pearson criterion. The contours of inhomogeneity zones detected by the group of receivers are presented for a number of practically interesting variants of relative positioning of the sources, receivers and inhomogeneous layer. The effect of spatial extension of the sources and inhomogeneous layer, as well as signal frequency band, on the inhomogeneity detection efficiency is considered. The model situation studied in this paper reflects some characteristic features of forming and propagation of acoustic signals in human respiratory tract with pathological modifications of the lung tissue (parenchyma). In so doing, the inhomogeneity layer is supposed to describe pathological changes in the parenchyma. |
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KEY WORDS: acoustic inhomogeneity layer, statistical problem of detecting a signal, uncorrelated interference, cross power spectral density, Neumann-Pearson criterion |
| TEXT LANGUAGE: Russian |