Cross Correlation in Structural Systems: Dispersion and Nondispersion Waves

Abstract

The use of cross correlation as a tool for analyzing propagation of energy in structural systems is investigated. Each energy-transmission path will have a characteristic delay time, and examination of the cross-correlation function of input and response can guide in the determination of the most significant path or paths. Difficulties occur in distributed systems or when the propagation is by a dispersive mechanism. The principles of correlation analysis are examined for both dispersive and nondispersive systems. Experimental evidence is presented that supports the theory and concepts developed. On the basis of these preliminary results, it appears that the technique holds promise and bears further investigation.

Core Noise Diagnostics of Turbofan Engine Noise Using Correlation and Coherence Functions

“…20 The cross-correlation function was used to detect periodic signals in noise by Lee (1950). 21 White (1969) 22 used the cross-correlation function and filters to look for propagation time delays in a system with periodic signals.…”

Experimental Measurement of Picometer Scale Spontaneous Vibrations in a Precision Deployable Boom under Thermal Loading

“…Causality analysis is an analytical method that is often employed in finding the vibration sources and it is very useful in structures with either a few vibration transmission paths or a continuum of transmission paths. However, for structures with a large, finite number of transmission paths, the analysis technique becomes excessively ambiguous, and hence not useful [17]. The IPEX boom contains many battens, longerons and tensioned diagonals making a large but finite number of transmission paths.…”

Control Valve and Regulator Noise Generation, Propagation, and Reduction

“…15 These results were obtained by crosscorrelating filtered ve-Iocity fluctuation measurements (see Ref. 16), using hot-film anemometers in the turbulent-mixing region, with the filtered wall-pressure fluctuations far downstream from the orifice in the fully developed acoustic region inside the pipe. The method is also described by Barger (Ref.…”

“…The designer of new plants involving the control and transport of highpressure gas flows in the chemical, petrochemical, and power (16) plant industries is faced with the need for specifying a piping system that will meet the noise exposure requirements stipulated in the Occupational Safety and Health Act. He must therefore be able to predict the noise environment in the plant, and particularly at locations where operators are stationed for any length of time.…”