Objectively measured and subjectively perceived distortion in nonlinear systems.

A method for measuring nonlinear distortion, which is applicable to almost any transmission system and which can use any input signal as a test signal, is proposed. The method exploits the fact that a pair of signals, generated to form the real and imaginary parts of the analytical signal corresponding to the input signal to a system, lose their property of being a Hilbert pair after being passed through a nonlinear system. The method was tested by measuring 12 different hearing aid compression systems. These objective measurements were compared with the subjectively perceived amount of distortion, assessed by a group of 10 otologically normal subjects. A reasonably monotonic relation between the subjective and objective measures of distortion was observed. The objective Hilbert pair based measure can be related to both traditional total harmonic distortion and traditional signal to noise ratio.