[LAD] Floating point processing and high dynamic range audio

[Philipp Überbacher]

Excerpts from fons's message of 2010-07-22 02:24:04 +0200:
> On Thu, Jul 22, 2010 at 01:05:01AM +0200, Philipp Überbacher wrote:
> 
> > I think the word loudness is a problem here. Afaik it usually refers to
> > how it is perceived, and twice the amplitude doesn't mean twice the
> > perceived loudness. It may mean twice the sound pressure level, energy,
> > or intensity (if we ignore analogue anomalies, as you wrote in some other
> > answer).
> 
> Subjective loudness is a very complex thing, depending on the
> spectrum, duration, and other aspects of the sound, and also
> on circumstances not related to the sound itself.
>
> For mid frequencies and a duraion of one second, the average
> subjective impression of 'twice as loud' seems to correspond
> to an SPL difference of around +10 dB. 

I had a brief look at the section about loudness in musimathics and it
mentions 10 dB based on the work of Stevens, S.S. 1956,
"Calculation of the Loudness of Complex Noise" and 6 dB based on
Warren, R. M. 1970,
"Elimination of Biases in Loudness Judgments for Tones.".
I think I've encountered the 6 dB more often in texts, which doesn't
mean it's closer to the truth, if that's possible at all.
Knowing a 'correct' number would be nice for artists and sound
engineers, but if it varies wildly from person to person, as Gareth Loy
suggests (no idea where he bases this on) then this simply isn't
possible. Picking any number within or around this range is probably as
good as any other.

> I often wondered what criterion we use to determine which 
> objective SPL difference sounds as 'twice as loud'. We don't
> have any conscious numerical value (there may be unconscious
> ones such as the amount of auditory nerve pulses, or the amount
> of neural activity), so what it this impression based on ?
> 
> The only thing I could imagine is some link with the subjective
> impression of a variable number of identical sources. For example
> two people talking could be considered to be 'twice as loud' as
> one. But that is not the case, the results don't fit at all (it
> would mean 3 dB instead of 10).

I never thought about that to be honest. It's immensely complex. It
might have to do with each persons hearing capabilities, for example the
bandwidth of loudness perception or the smallest discernible loudness
difference. If it really is very different from person to person, then
an explanation that takes the different hearing capabilities into
account could be sensible, don't you think?

> > It may be nitpicking, but I found it important to differentiate
> > between the physical phenomenon and the perception.
> 
> Not nitpicking at all...
> 
> Ciao,
> 
> -- 
> FA
> 
> There are three of them, and Alleline.

Good night :)
-- 
Regards,
Philipp

--
"Wir stehen selbst enttäuscht und sehn betroffen / Den Vorhang zu und alle Fragen offen." Bertolt Brecht, Der gute Mensch von Sezuan