On Aug 10, 3:22 pm, Jud McCranie
wrote:
On Fri, 10 Aug 2007 01:27:18 -0400, mm
wrote:

I've never heard this before. AFAIK, a 10 decibel increase is twice
the volume. It was chosen that way to be a round number, 1 bel.

I looked it up, and a 3 dB increase approximately doubles the power.
--
Replace you know what by j to email

Yes this got far too complicated; very quickly.

From a practical point of view a difference between 52 and 54 Decibels
will not be discernible to most ears.

And some of the posted info. was wrong/incomplete!

Several comments reference to Decibels.

1) The decibel is of course one tenth of a Bel. The Bel is defined as
"The logarithmic ratio of two powers (volumes)". It is a unit of
comparison named after Alexander Graham Bell a Scottish immigrant who
invented the telephone in Canada.
2) If you double the power (volume of sound etc.); The logarithm of 2
is 0.3; or 0.3 Bels. Which is of course 3 Decibels!
3) The third thing wrong is that Bels/Decibels etc. are a 'comparison'
or ratio of two powers, or in this case, two volumes.

It is incorrect to say something is X Decibels.

The question is immediately 'In relation to what'.
So the dish washer is 50 something decibels louder than, what???????
Dead silence? A mouse squeak???? A teenager's ghetto blaster at full
volume?? A loud motorbike next door????? A radio plying very quietly
as you drop off to sleep????

Decibels have to be referenced to something.
Anyone reading car magazines such as Car and Driver may have noticed
that they will say that the sound level inside the cabin of a certain
vehicle is say 75Dba. While another vehicle which is twice as loud,
say, has a sound level of say 78Dba.
That tells us that the measurement (comparison) is Decibels and that
it is in reference to some agreed standard of "Zero Dba".

There are number of different references used by different industries/
types of technology.

The reason for Decibels is; a) Convenience; think back to adding and
subtracting logarithms in school and then anti-logging the result!
Right; remember that? We 'did logarithms' around about age 14 IIRC.
About grade 8 or 9? b) Logarithmic response is the way the human ear
works.

So if two people are hammering on a wall rather than one person
hammering on a wall it will be TWICE as loud and therefore 3 Decibels
Louder. And humans will be able to perceive the difference in noise
level. OK?