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In Reply to: RE: -75 dB posted by bjh on June 25, 2014 at 13:19:12
What a -75 dB null means is the difference between the two was 1 part in about 30,000,000.
If one were to change the level of the signal you were listening to by that amount, it would be a change of about 1.4^-8 dB, or "pretty small".
If you're working up to say something then by all means spit it out.
Never trust an Atom, they Make Up everything!
I am not sure what you mean but I can explain without using dB which is a log scale and can be confusing.
As the dB scale is commonly used, maybe explain that would be better.
dB in this use refers to the difference between two things, a 3dB difference is a factor of two in power, 6dB is 4 times, 12dB is 16 times, 20dB is 100 times, 60dB is a million times.
So, if the distortion in an amplifier were -40dB down from the real signal, the THD would be about 1/10,000 the power or level of the desired signal or 1/100 the Voltage level.
-75 dB here means the difference between the two is about 1/30,000,000 the power of the desired signal.
Is that much change audible?
Now this is more complicated because ears are not microphones, what we experience as “audible reality” is FAR more than just the sound pressure reaching ones ears and includes what we see and know as well.
It is the lifetime of hearing that has allowed us to learn to use all the weird things our ears do as a function of angle and height, to create the 3d mental image we experience as reality.
That stuff is usually disconcerting to audiophiles as we know nothing else but that experience and yet it is also well known to audiologists that our ears aren’t “flat” in their frequency response at all and have all kinds of complications.
Hope that helps
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