On Thu, 09 Aug 2007 12:33:53 -0700, RickH
wrote:

On Aug 9, 1:10 pm, Jud McCranie
wrote:
Our Kenmore dishwasher that is 10-11 years old is making a noise like
it isn't going to last much longer, so we are replacing it. I've
looked at several models, but I'm leaning toward a couple of Bosch
dishwashers. One is rated at 52 dB but comes only in black. The
other is rated 54 dB, but comes in black/white/stainless steel.
Stainless steel would match our refrigerator. Is there much
difference between 52 dB and 54 dB in a dishwasher?
--
Replace you know what by j to email

Every 6db is a doubling in the volume, so going from 0db to 6db is
twice as loud, going from 6db to 12db is another doubling of the
volume making 12db four times as loud as 0db, going from 12db to 18db
is another doubling, making 18db eight times as loud as 0db.

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 verified this by looking the URL's you gave in your second post,
although maybe they don't say it quite the way I have.

http://www.gcaudio.com/resources/howtos/loudness.html does say,
however, that 2 bels, 20 decibels, is about 4 times as loud, and 30
decibels is about 8 times as loud. All of these measures of loudness
or volume -- not sure which is the better word -- are as perceived by
our ears, the ears of healthy people. (Or our ears on average, if
they vary much from one healthy person to another. Maybe that is why
the chart says "about", rather than "exactly".)

The scale is logarithmic because of the way our ears and brain work
together. If we only went by the energy or force or whatever that
went into making sound, it would be misleading. A sound that is the
result of twice as much energy does not sound twice as loud. The
difference seems to be a lot less than that.

Same thing in the opposite direction. When we hear a tiny sound,
maybe the sound of a pin hitting the floor, or a leaf, it's thousands
of times less strong than normal talking, but it doesn't sound like
that to us. The sound is smaller, but not that much. It's still
clear.

I've often thought that the reason it works that way is because of the
three bones in the ear, and that one of them is moved when the general
level of sound is higher or lower, to move the fulcrum and change the
mechanical advantage of the ear bones. So that small sounds can sound
louder and loud sounds can sound less loud.

OTOH, it might not be the bones at all but the brain.

One guy with the kind of background to know told me that I'm wrong,
it's not the bones, but typically I'm not yet convinced. I asked
several physics Ph.D's what happened to light after it was no longer
light in a sealed room, and didn't it turn in to the same amount of
heat that it took to make the light in the first place, and all but
one either couldn't say, or thought the answer was no. One thought
the answer was yes, and I'm pretty sure he and I are right.

I guess the reason I think it is the bones is that we could have
gotten by with only 1 or 2 bones, I think, if they were only going to
transmit sound from the eardrum to some nerve. The purpose of the
third bone is not strength. They are all barely attached to anything
else afaik. The purpose seems to me to absolutely be some kind of
regulation, automatic volume control, similar to other mechanical
controls I've seen but forgotten throughout my life, especially before
electronics was so dominant.

The volume control on a Victrola we had for a while was the segmented
door, like the lid on a roll-top desk, that could be pulled in front
of the wooden horn, in models where the horn was not atop the tone arm
but below it in the cabinet. Really only one part involved there, and
the phyical volume control was arithmetic, not geometric or
logarithmic.

The iris on a camera, modeled right after the iris in our eyes,
decreases the area available for light to enter by the square of the
diameter. That's it. That's what I compared the bones of the ear
too, but I think they might be more powerful if the fulcrum really
moves.

Maybe I asked the wrong question to the guy I talked to about the ear.
Does the fulcrum move? I should have stuck with objective questions
instead of asking about conclusions.

IIRC the steam/speed/power control on a steam locomotive is a little
more complicated than what I expected, but I don't remember if it is
comparable to a 3 part device like the ear.

I'm pretty sure I've seen other mechanical controls more complicated
than an iris or locomotive, maybe involving three parts and but my
memory is a blank now.


If the fulcrum in the ear doesn't move sometimes, we do we have 3
bones and not just one (or two, but I'm not sure what the second does
or would do)?



(assuming 0 db is the volume you call "normal" or your zero
calibration point which can be any thing you want to calibrate it to).

So for example if you calibrate the sound of a cricket at 10 feet to
0db, then you increase to 18db the cricket will be 8 times as loud as
"normal".

So a difference of 52db to 54db would be about 33% louder, most folks
would hear that easily.

Since 2db is one fifth of 10 db, it woudl be the fifth root of 2, to
give the ratio; minus 1, to give the fraction louder; and times 100
percent to give the percentage louder. The fifth root of 2 is a
little under 1.2, so a little under 20%. Checking with a calculator I
think 1.15 to the fifth power is a little over 2, so about 15% louder,
though how that converts to the way people would perceive it, I'm
still not sure. I guess we've already allowed for the hearing oddity
of people by using decibels, but now we're converted it back to
loudness -- read that ENERGY -- so I think that removes the advantage
of using bels and decibels. It removes the reason they were invented
in the first place, to provide a number that would correspond to our
hearing, as opposed to the amount of energy used in making the sounds.

So even though I willingly did it at the start of the paragraph, I
think it is misleading to convert back to energy. What we should do
is learn to understand, to have a good feel for what a decibel
represnets. Their purpose is to represent sound, but the problem is
that we don't have ongoing feedback of how loud in decibels something
is.

After measuring and experience and practice and visualizing, we know
an inch when we see one. We can see two inches and know that
something is twice as long as an inch. But even if we memorize the
charts that you yourself pointed us to in your second post, we don't
really appreciate how loud 20 db are, and even less so the ratio of
two levels of sound, or, given one sound and a decibel difference, the
level of the second sound.

I'd say that in general, we can visualize things much more than we can
audiolize things. Maybe that's why there is no word audiolize.

I went shopping for a furnace the only spec I cared about was db, the
salespeople thought I was nuts.

I don't think you're nuts.

I'm glad you just gave me the idea, and I hope by the time I need a
furnace, they will rate them by loudness. They probably won't,
though.

I have a 3 speed indoor furnace fan, only adjustable by connecting a
different wire to the power. It's too loud, but it's set on the
slowest speed. I changed it anyhow, on the slim hope the schematic or
the color was wrong, but they weren't.


I told them I care less how efficient
it is, I want the quietest one regardless of energy. Unfortunately
the manufacturers could not even tell me their db ratings (Trane,
Bryant, Lennox, etc)