|
in the following article,the person who answered the question did not take [area of mouth opening] into account
|
It
appears the author did - from the article cited:
|
80 decibels produces .001 watts of energy(sic)
|
... the intensity from the sound would be in watts per square meter.
80dB would be about 1x10
-4Wm
-2 ... so he seems to have used an area of about 10m
2 ... which seems a little large. Perhaps the author has a big mouth?
The whole thing is suspect isn't it - I'm sure I can make myself heard in the front rows of a rock concert - well, by yelling in someone's ear.
If I yell at a cup of coffee the same intensity that is more like 0.1Wm
-2. Figure a mouth area of about a square decimeter
(0.1m x 0.1m = 0.01m
-2) and that's 0.001W directed at the cup.
So the final figure is about right.
ref.
http://www.physicsclassroom.com/class/sound/u11l2b.cfm