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

A method for measuring a change in a pitch or a frequency from an audio device, wherein the audio device having an input terminal and an output terminal, comprising:

• coupling to the input of the audio device a test signal comprising a modulated signal wherein the modulated signal includes a first modulating signal, a first carrier signal, and wherein the first carrier signal is modulated by the first modulating signal;
• the modulated signal having a first pitch variation or a first frequency variation of the first carrier signal, wherein the first pitch variation or the first frequency variation of the first carrier signal is determined by the first modulation signal;
• coupling an output signal from the output terminal of the audio device to an input terminal of a demodulator to measure the change in the pitch or the change in the frequency at the output terminal of the audio device and further comprising an output terminal from the demodulator to provide a signal indicative of the pitch variation or the frequency variation from the output of the audio device, wherein the pitch variation or the frequency variation from the output of the audio device is changed from the first pitch variation or is changed from the first frequency variation;
• wherein the audio device includes a digital audio device including data compression and wherein the test signal includes a frequency modulated signal that generates sideband signals related to the test signal and wherein the output of the audio device attenuates one or more sideband signals, and wherein the output of the audio device provides a change in pitch different from a change in pitch of the test signal.

An apparatus for measuring a change in a pitch or a frequency from an audio device, wherein the audio device having an input terminal and an output terminal, comprising:

• coupling to the input of the audio device a test signal comprising a modulated signal wherein the modulated signal includes a first modulating signal, a first carrier signal, and wherein the first carrier signal is modulated by the first modulating signal;
• the modulated signal having a first pitch variation or a first frequency variation of the first carrier signal, wherein the first pitch variation or the first frequency variation of the first carrier signal is determined by the first modulation signal;
• coupling an output signal from the output terminal of the audio device to an input terminal of a demodulator to measure the change in the pitch or the change in the frequency at the output terminal of the audio device and further comprising an output terminal from the demodulator to provide a signal indicative of the pitch variation or the frequency variation from the output of the audio device, wherein the pitch variation or the frequency variation from the output of the audio device is changed from the first pitch variation or is changed from the first frequency variation;
• wherein the audio device includes a digital audio device including data compression;
• wherein the test signal includes a frequency modulated signal that generates sideband signals related to the test signal and wherein the output of the audio device attenuates one or more sideband signals, and wherein the output of the audio device provides a change in pitch different from a change in pitch of the test signal.