Decibals
 

In our house there are 3 recievers hooked up to different stereo systems. I've had to fiddle with all of them from time to time to get them to work properly, and one thing I've noticed on them is how the sound measurement always goes from 100 up to 0 dB. Does anybody know why this is? I've been wondering about it for quite some time.

No, and frankly, I've often wondered the same thing.

It is especially confusing since the decibel scale is logrithmic as opposed to linear.

In other words, when measuring sound energy, every 10 decibels is represents a tenfold in increased sound energy. This means going from say 60dB to 80dB does NOT represent a 20 fold increase in energy, but rather a hundred fold increase (60 to 70 = 10 fold, 70 to 80 = 10 fold, 60 to 80 = 10x10 = 100 fold).

So anyway, it appears to me to be a linear relationship when I crank the knob on my stereo, so I really don't get inverse dB's as a stereo volume scaler.

Decibels are meaningless without a reference level. For your stereo, the reference is the power at maximum volume. Here, dB=10*log(Pmax/P). When you crank up the volume, P increases until it's equal to Pmax, giving a dB of 0.

I'm not sure how to relate power to apparent sound volume, but my guess is that there is an exponential relationship, P^2 or P^3 or something. In that case, a linear increase in dB will give a linear increase in percieved volume.

I've noticed the sound increase not being linear, but I didn't imagine there would be math involved like that.....

The decibel scale is logarithmic partially because our ears don't work linearly. We can hear sound intensities over something like 12 orders of magnitude between the faintest whisper and a painful rock concert.

I guess you learn something new everyday....