On Mon,5/23/2016 6:36 AM, brian wrote:
1 dB is generally agreed upon to be the minimum detectible difference
in audio that people can detect.
Of course, these measurements don't include QRM, QSB or AGC action.
Exactly right on both counts. That "generally agreed" is actually the
result of research done nearly a century ago.
For absolute level (loudness), it takes a change of 6-10 dB to be
perceived as "twice as loud" or "half as loud." But when the desired
signal is near the level of noise or other signals, a change of only a
dB or two can make a BIG difference in whether or not we make the QSO.
One of the things I did professionally was mix live sound, both for
sound reinforcement and recording/broadcast. When a given instrument or
voice needed to be louder to balance well, the needed change was rarely
more than a dB or two unless I had the mix very wrong to begin with or a
musician changed something a lot (like moving too far from the mic, or
playing a different instrument).
So -- when conditions are marginal (on the edge of the other guy's
noise), every dB matters. That's why the best operators work to optimize
their antenna systems and squeezing every last dB of loss out of the coax.
73, Jim K9YC
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