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That maybe true in your perception. Still my first statement is not all that wrong. With communication receivers that I deal with have high pass filters centered near 300Hz along with low pass filters to filter above about 3000Hz. So if a 100Hz signal is causing interference, it should not be heard if it is passing through the audio block. I did forget that there is means for a low frequency(below 300Hz) signals can bypass the audio block and get to a speaker. Even still the quality of speakers in low tier CB radios probably do not have that great of a frequency response. Then also a harmonic of the 100Hz signal if large enough could pass through the audio block.
LIke I said I never intended to get off on a tangent on audible or hearable signal levels and human hearing response. I still thought that I was in part correct with my first statement that a 100Hz signal is at the low end of "hearable" and is best detected with a scope. What I did forget is that the third harmonic and greater would be very audible. I findeed that were the case.
If I am at fault of anything it is not taking enough to to be more explicit and to general in my comments.
james