[Nika]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:<HR>Originally posted by QuikDraw:
This is simply not correct. If the creation of these subtones were a function of the ear, and are not an actual electrical component of the output signal resulting from the mixing of two tones, then the science behind that could be applied just as correctly to higher frequencies as well. If that were true then a superhetrodyne radio receiver would not work.

To simplify, a superhet combines radio waves from an antenna with a set Intermediate Frequency ocsillator and then filters out all but either the sum or the difference frequency, leaving only one of these (supposedly only produced in the human ear) subtones for further processing in the receiver.

No, these subtones, the sum and difference frequencies of the two mixed tones, are a real electrical component of the output signal. Mix two sine waves, both within range of your digital system, and also whose sum and difference frequencies lie within your digital range, and look at the result in a spectrum analyzer. You will see all 4 frequencies!

Mike<HR></BLOCKQUOTE>

Sorry, I should have been more specific.

I should have stipulated that this only happens in a non-linear system. In a linear system the distortion that causes these tones does not manifest until it hits the non-linearity of the ear. Thus, the properties we are discussing are indeed caused by the non-linearity of the ear, but that is not the only place that they can happen. IM distortion is a property of any non-linear system - including the air. But the non-linearity is so small on any of these systems that it is undectable by the ear.

With the systems that we are talking about, indications of IM distortion may indeed show up on a spectrograph, but will be undectable by the ear. As soon as both tones are in the ear's range, however, the distortion components become audible.

I hope that this clarifies the phrase of contention. If in doubt, try it.

Nika.