Effect of a high-pass filter on triple correlation measurements

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Abstract
An experimental investigation has been made of the effect of a high-pass filter on triple correlation measurements. A random noise signal with a non-symmetrical distribution is generated and passed through a variable high-pass filter. The triple correlation (originally symmetric in time) is measured as a function of cut-off frequency using a modified averaging device. It is found that the high-pass filter introduces a perturbation, anti-symmetric in time, of order ωt / ω0 , where ωt is the filter frequency and ω0 the typical power spectrum frequency. These results agree with an approximate mathematical analysis. It is concluded that the symmetric part of the triple correlation observed in some measurements of fluid turbulence cannot be due to a high-pass filter.