Separation of Core Noise and Jet Noise

Abstract

A method of identificatio n and measurement of c*re W\«» and let noise separately has been developed based on cross-correlation of signals from microphones located at yi<<My sep 4?ated angles in the far field of a jet. The different coherent properties of core noise and jet! v\o»<*? Aft *&&L fa ^H^ method to achieve this separation. Experimental data obtained in a small scale facility ara 3v&tyt& t$ ^e$tanstrate that this method can be used successfully to separate the mean-square pressures of ccnre «0ise and jet fx/jf^ Nomenclature A = autocorrelation function C = cross-correlation function or Doppler factor in Eq. (3) M = Mach number TV = index in Eq. (10) p = sound pressure q = source fluctuation, Eq. (10) r = radius 5 = spectral density t =time t' = retarded time U,V = velocity W - speed of tape recording a = ratio defined in Eq. (4) /3 = ratio defined in Eq. (5) 6 - density exponent A = difference 6 = angle with respect to the downstream jet axis 0 = angle to the direction of motion (Fig .13) p - density T = time delay \l/ = autocorrelation of moving source w = ciruclar frequency Subscripts and Superscripts