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godsinhisheaven 2 days ago

This doesn't make any sense to me. Isn't this completely backwards? Wouldn't this behavior be expected from a logarithmic knob, and not a linear knob? I know what a logarithmic curve looks like, it rises quickly and then it tapers off, exactly the behavior you describe. But then you attribute that to a lineae knob! The parent comment confuses the hell out of me too, I am just really not putting 2 and 2 together here.

msandford 2 days ago | parent | next [-]

You're missing a critical piece of information. Human hearing (and vision) are logarithmic sensors.

Ears can register sounds from maybe 20-30 dB upwards of 120ish which isn't a factor of 4-6 in terms of power but rather a factor of 120-30=90 decibels or 9 bels or 10^9 or one billion.

Because your ears have absolutely enormous range you need the potentiometer (pot) to have a logarithmic taper to it. The amplifier has an essentially fixed amount of amplification so that's a fixed sound dB output. Your ears can hear a vast range. A linear pot essentially locks the entire output into the same 10 decibels as the amplifier maximum output through its linearity. Once you've turned it to 10% of the range it has precisely 10 decibels worth of range left. If you want to turn the volume down by 40 decibels you have to do that within the 0-10% part of the pot's range.

A logarithmic pot will give you maybe 40-60 decibels worth of adjustment by dividing things up differently. Every 20% of the range increases the output not by 20% but by a factor of 10 let's say. That gives you a pot with a range of 50 decibels which is enough that it roughly matches the absolutely miraculous range of the ear.

hansvm 2 days ago | parent | prev | next [-]

"logarithmic" here refers to the number on the scale being logarithmic in the sound pressure level. Restated, power is exponential in the knob value, which roughly matches human perception of a linear increase. An actual linear function is far too slow.

godsinhisheaven 2 days ago | parent [-]

Got it, so the sound pressure is logarithmic, but the sound power is exponential, and you can control both at once with one knob, and they, align, quite well I guess.

brazzy 2 days ago | parent | prev [-]

The point is that sound perception is logarithmic. You perceive a 10 times stronger air vibration as twice as loud. So if you have a knob that increases the power that produces the vibrations linearly, you hear a logarithmic increase.

You need a knob that increases power exponentially to hear a linear increase in loudness.