AB, of course when distortion gets high enough it can be heard as a difference in sound. How high is "high enough" depends to a large extent on what type of material is being reproduced. On music, testing has shown that THD has to be higher than 1%(sometimes 2-3%) before a difference is identified in blind tests. There's no way that distortions so far below the threshhold of audibility as .04% and .08% could be differentiated. They would have to be at least 20 times as much. So yes, of course very high levels of noise and distortion, along with big frequency deviations could be heard, but they don't occur in well-designed equipment, whether it costs $200 or $2,000.
