billfitzmaurice said:
Obvious Oversight #277: If watts measured sound levels why are light bulbs wattage rated?
Watts measure power... or was that a joke?
Decibels measure sound level...
Where I = P/A
L = 10log I/Ref.
P = Power in watts
A = area away from the sound source
I = Intensity
L = Sound level in decibels
Ref = Reference intensity (10^-12 W/(m^2))
So using that... cant u make a direct relation from wattage to decibels by rearranging to get
P = A x Ref. x 10^[L/10] ref = 10^-12
And, i dont know much about speakers and bliz-blazz about watts n whatev... but... it would seem to me... that if your speaker is on the floor, and for this purpose we can count the floor as a infinite baffles (absorbing no sound) .. then the point source of the speaker would radiate into a half sphere (2pi - sterradians) and we take the measurement in dB from 1 metre away (like you guys say is the reference distance)
A = 2 x pi x r^2 where r =1
A = 2pi
P = 2pi x 10^-12 x 10^[L/10]
so P = 6.28 x 10^-12 x 10^[L/10]
So if you have a speaker rated at 1000 W
1000 = 6.28 x 10^-12 x 10^[L/10]
1.59 x 10^14 = 10^[L/10]
L = 10 log [1.59 x 10^14]
L = 142 dB
Which of course would cause massive hearing damage or make you go deaf
so, i dunno what happened there...
But i guess if you account for the fact that the human ears are less sensitive to the bass frequencies, and no one is gonna blast their 1000 W cab at full volume and stand a metre away to see whaddup..... i guess it all works out, now a 1000W guitar cab is much different.... ouch
