Coherence analysis applied to structural acoustic problems

Abstract

This presentation discusses signal processing techniques and engineering requirements for solving structural acoustic multiple input/output problems using ordinary, partial, and multiple coherence functions. Practical matters are included on formulation of models, selection of input records, time delay bias errors, measurement interference effects, and statistical sampling errors. These topics are covered in the book by J. S. Bendat and A. G. Piersol [Engineering Applications of Correlation and Spectral Analysis (Wiley-Interscience, New York, 1980)]. Recent two-input/one-output models employing these methods are: (1) space shuttle tile problems where it is required to determine the response of tiles due to pressures from acoustic noise inputs over the tiles, versus that from correlated panel vibration inputs under the tiles (performed by A. G. Piersol); (2) a noise source identification problem where it is required to determine the relative contributions of a structure-borne noise input generated in an engine, versus a correlated cooling fan noise input from a fan mounted on the engine, to a farfield sound output (performed by W. G. Halvorsen).