This is quite an interesting question! First, I assure you that there
is a purpose behind displaying the volume this way. In fact, it is a
more precise way to describe the volume of sound than the
"conventional" method of displaying louder sound as a higher number.
A good explanation (and why it is better than the "conventional" way)
is as follows:
"Why does the volume knob have 0 decibels at the top? Well, let's see
what happens if we put 0 decibels at the bottom, and count up from
there. The only thing 0 decibels could mean is "no sound": when the
volume is turned all the way down, no sound comes out. If you went up
10 decibels, or 1 bel, then you'd expect 10 times as much sound to
come out. Unfortunately, 10 times 0 is 0, so you'd still get no sound.
Hopefully you didn't spend all that money on your fancy stereo just so
you could get no sound out of it.
Let's try it the other way, with 0 at the top. The only thing 0
could mean at the top of the dial is "maximum volume," where your
amplifier is amplifying as much as it possibly can. If you went down
10 decibels, or 1 bel, then you'd get one tenth of your maximum
volume. If you went down another 10 dB, you'd get one hundredth of
your maximum volume. Another 10 dB down, and you'd have a thousandth
of your maximum volume. This is sounding much more useful. If you went
all the way down to 100 dB below maximum volume, then no matter how
loud your fancy amplifier is, one ten billionth of its maximum volume
would be sufficiently close to "no sound" that you wouldn't notice it.
[ http://mozart.fiction.org/2001-05-06.html ]
So, when the stereo is putting out the maximum volume that it can
produce, the display reads zero dB, and you need to think of the
negative values on the display as relative to that absolute maximum
value. The need for this system, if you want to be precise, stems
from the fact that you CAN precisely describe the maximum volume
(simply the wattage/power capacity of the unit) and delineate this as
a value, but because the relative unit of bels or decibels are used,
you cannot accurately describe a volume that is a magnitude greater
relative to a very quiet volume. This makes more sense if you have a
good understanding of the system used to describe relative vs.
absolute sound volumes, the decibel scale. An explanation of this
system can be found at:
[ http://www.tpub.com/content/neets/14188/css/14188_50.htm ]
Other stereo systems, those that do not display the figure in decibels
nor as negative numbers, usually have a number range that goes from
zero (quietest) to some arbitrary number generally between twenty and
one hundred. These numbers are completely arbitrary, and are just
used as a relative indicator of volume, but have the problems that are
accounted for by the decibel display system.
I trust this information has answered your question completely. If
there is a need for clarification, please request one before rating
this answer. Thanks for bringing your question to Google Answers!
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