Patent ID: 8704533

Claim:
Method of measuring an induced phase or frequency modulation effect of an audio device, wherein the audio device has an input and an output, comprising: coupling two or more signals of different audio frequencies into the input of the audio device; coupling the output of the audio device to an input of a modifier circuit or filter; coupling the output of the modifier or filter circuit to an input of an AM component removed circuit or function including a limiting amplifier, comparator, zero crossing detector, and or a Sgn(x) function; wherein an output of the AM component removal circuit or function effectively removes amplitude modulation sidebands that also provides remaining sidebands around a frequency of a signal from the output of the audio device for spectrum analysis, and wherein the remaining sidebands are indicative of a phase or frequency modulation effect; and providing spectrum analysis of the output of the device via the output of the AM component removal circuit or function which removes amplitude modulation sidebands, to measure the induced phase or frequency modulation effect for one or more signals at the output of the device, wherein the phase or frequency modulation effect on one of the input signals is caused or induced by one or more of the other input signals.