Method and apparatus to evaluate audio equipment for dynamic distortions and or differential phase and or frequency modulation effects

An apparatus for measuring a de-sensing effect on a phase response of an audio device, wherein the audio device having an input terminal and an output terminal, comprising:

• coupling to the input of the audio device at least two signals including at least a first signal, and a second signal wherein the amplitude of the first signal is larger than the amplitude of the second signal;
• coupling an output signal from the output terminal of the audio device to an input of a phase measuring system to measure the phase response of a signal related to the second signal at the output terminal of the audio device;
• providing a first phase response measurement when the first signal is adjusted to a first amplitude level and providing a second phase response measurement when the first signal is adjusted to a second amplitude level, wherein when the first signal is adjusted to the first amplitude level or when the first signal is adjusted to the second amplitude level the de-sensing effect is provided, and wherein the de-sensing effect changes the phase response of the signal related to the second signal at the output of the audio device.