Quadratic phase coupling detection using higher order statistics

Abstract

If a speech signal exhibits quadratic phase coupling (QPC) then this is a strong indication that the signal is produced by some nonlinear mechanism. QPC can be detected by testing for certain properties in the signal bicoherence, but previous measures based only on the magnitude of the bicoherence fail if certain phase randomization assumptions cannot be made. To get around this problem, the bicoherence phase can also be utilized. In the paper a QPC detector is described which comprises a magnitude test (based on the Hinich (1982) Gaussianity test) and a phase test (based on empirical results of Sebert and Elgar, 1989). A new visualisation of the problem is presented, and the properties of the QPC detector are investigated with some simulations.