Perception and Watts: Doubling of power


There's a curious rule of thumb, which to my ears seems mostly true:

  • To double the perceived volume, you must output 10x more power.

10x power = 10 dB by the way.  We've read this as we were buying amps and trying to decide between 100w/channel and 150w/channel.  We are told, repeatedly that 50 W difference isn't really that much.

On more than one occasion I've tested this and found it's pretty much spot on.  Here's my question:

How can any of us really tell what half as loud, or twice as loud is?

I mean, think about this for a bit.  I cannot tell half as bright, or twice as bright, but it seems I actually CAN tell what half as loud is.  How does this even begin to work in the ear/brain mechanism?? 😁

erik_squires

Lots of interesting discussion here, of course, but I really did just want to ask, how can we tell what twice as loud is?  I mean, I think I can, and it happens to match 10 dB.  WHY?  Our visual systems however seem very good at seeing twice the length or half the length, or finding the mid point on a line. Kind of weird that we also have a sense for half or twice as loud.

I also never really understood what was meant by “perceived” as sounding twice as loud…I figured it was too subjective, but apparently there are some safe generalizations too be made with the way human ears work.

@mrskeptic I agree

Here's a question, @johnnycamp5  - Lets say you play some music.  Can you turn it down by half?  Or can you turn it up to be twice as loud?  How do you know??

I mean, I can, and I think you can too!  but... how do we know what half is?

Good question!

I haven’t a clue…Ive also turned down and up the volume to what I figured was halved or doubled at output but I’ve never measured the decibel levels during.

Another excuse to play with one of my frivolous measurement devices!