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On 07/22/2010 05:31 AM, Philipp Überbacher wrote:
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<title>Re: Floating point processing and high dynamic range audio</title>
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Excerpts from Philipp Überbacher's message of 2010-07-22 03:16:00
+0200:
<div class="shrinkable-quote"><br>
> Excerpts from fons's message of 2010-07-22 02:24:04 +0200:
<br>
> > On Thu, Jul 22, 2010 at 01:05:01AM +0200, Philipp Überbacher
wrote:
<br>
> > <br>
> > > I think the word loudness is a problem here. Afaik it
usually refers to
<br>
> > > how it is perceived, and twice the amplitude doesn't
mean twice the
<br>
> > > perceived loudness. It may mean twice the sound pressure
level, energy,
<br>
> > > or intensity (if we ignore analogue anomalies, as you
wrote in some other
<br>
> > > answer).
<br>
> > <br>
> > Subjective loudness is a very complex thing, depending on the
<br>
> > spectrum, duration, and other aspects of the sound, and also
<br>
> > on circumstances not related to the sound itself.
<br>
> >
<br>
> > For mid frequencies and a duraion of one second, the average
<br>
> > subjective impression of 'twice as loud' seems to correspond
<br>
> > to an SPL difference of around +10 dB. <br>
> <br>
> I had a brief look at the section about loudness in musimathics
and it
<br>
> mentions 10 dB based on the work of Stevens, S.S. 1956,
<br>
> "Calculation of the Loudness of Complex Noise" and 6 dB based on
<br>
> Warren, R. M. 1970,
<br>
> "Elimination of Biases in Loudness Judgments for Tones.".
<br>
> I think I've encountered the 6 dB more often in texts, which
doesn't
<br>
> mean it's closer to the truth, if that's possible at all.
<br>
> Knowing a 'correct' number would be nice for artists and sound
<br>
> engineers, but if it varies wildly from person to person, as
Gareth Loy
<br>
> suggests (no idea where he bases this on) then this simply isn't
<br>
> possible. Picking any number within or around this range is
probably as
<br>
> good as any other.
<br>
> <br>
> > I often wondered what criterion we use to determine which <br>
> > objective SPL difference sounds as 'twice as loud'. We don't
<br>
> > have any conscious numerical value (there may be unconscious
<br>
> > ones such as the amount of auditory nerve pulses, or the
amount
<br>
> > of neural activity), so what it this impression based on ?
<br>
> > <br>
> > The only thing I could imagine is some link with the
subjective
<br>
> > impression of a variable number of identical sources. For
example
<br>
> > two people talking could be considered to be 'twice as loud'
as
<br>
> > one. But that is not the case, the results don't fit at all
(it
<br>
> > would mean 3 dB instead of 10).
<br>
> <br>
> I never thought about that to be honest. It's immensely complex.
It
<br>
> might have to do with each persons hearing capabilities, for
example the
<br>
> bandwidth of loudness perception or the smallest discernible
loudness
<br>
> difference. If it really is very different from person to person,
then
<br>
> an explanation that takes the different hearing capabilities into
<br>
> account could be sensible, don't you think?
</div>
<br>
I did find some more approaches to the problem, but those are just
<br>
ideas. From my personal experience I have to say that I have a very
hard
<br>
time saying when something is twice as loud. A musically well trained
<br>
person might have an easier time, I wouldn't know, but for me twice as
<br>
loud is something that is very vague. This might already explain the
<br>
large deviation between subjects as described in musimathics. It lead
me
<br>
to another idea though, the evolutionary perspective. Evolutionary it
<br>
likely never was important whether a sound is twice as loud. The only
<br>
situation I can imagine where judging loudness probably was important
<br>
is judging distances. How far is the animal I can't see, be it prey or
<br>
predator, away from me? We know that this takes more than the SPL into
<br>
account, and 'twice as loud' doesn't have relevance in this context. So
<br>
maybe the loudness perception is linked with spatialization.
<br>
</blockquote>
<br>
I think this is a very interesting idea. Could this be linked to some
kind of<br>
avarage SPL of all the sounds human beings are exposed to (and this
variable<br>
changes throughout history). Because when we try to judge the distance
of<br>
a barking dog, our brain would use the knowledge of all other dogs we
heard<br>
barking before, to estimate the distance of that dog. If we never heard
a dog<br>
before, maybe we would use the sounds of other animals as a reference,
and so on...<br>
<br>
greetings,<br>
<br>
Lieven<br>
<br>
<blockquote
cite="mid:tag:old.nabble.com,2006:post-29235348@localhost.localdomain"
type="cite"><br>
My other ideas are rather stupid, just ways to get the right numbers
for
<br>
your two person idea.
<br>
I simply used ln instead of log and got 7, but that's not even Neper
and
<br>
has no relevance.
<br>
<br>
The other idea of that kind is to assume a field quantity, which would
<br>
result in 6 dB. I'm still easily confused about 10*log and 20*log, but
I
<br>
think 20*log is usually used for sound pressure, but maybe not for
<br>
psychoacoustic effects.
<br>
-- <br>
Regards,
<br>
Philipp
<br>
<br>
--
<br>
"Wir stehen selbst enttäuscht und sehn betroffen / Den Vorhang zu und
alle Fragen offen." Bertolt Brecht, Der gute Mensch von Sezuan
<br>
<br>
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