[LAD] A little quiz about audio measurements...

[Gabriel M. Beddingfield]

On Fri, 28 May 2010, Ralf Mardorf wrote:

>>> The 100 Hz (being 2x 50Hz, the power freq. in Italy)
>>> suggests that it is probably related to some manner of
>>> power supply.  However, I have no theory why we're
>>> getting 2x 50Hz (and I think I need one :-)).
>>> 
>> 
>> Doh!  When the AC wave is rectified, it results in a signal that is 2x
>> the freq. because the negative part gets inverted.  That's why we see
>> 100 Hz instead of 50 Hz.
>> 
>> -gabriel
>> 
>
> On card A or X?

X.  A has already been "proven" -- unless it's a trick 
question that we can't trust that "proof."

> Why AM and not additive signals?

Because the peaks shift with the input signal.  If the 
signals were just added (mixed) then the peaks would always 
be at 100Hz, 200Hz, 300Hz... etc. and have the same 
amplitude.

Try modelling it up with AMS (that's what I did).

-gabriel