22 Jul
2010
22 Jul
'10
10:06 p.m.
On Thu, 2010-07-22 at 21:31 +0200, lieven moors wrote:
On 07/21/2010 07:24 PM, Fons Adriaensen-2 wrote:
For microphones there usually are -10 dB pad and a lot of engineers feel
around -6 dB half as loud. I guess this are usual values regarding to
experiences by audio engineers. So even audio engineers can hardly say
what their subjective feeling is. If you take a lot of people and you do
lab tests, I guess the results will be very confusing.
On Thu, Jul 22, 2010 at 01:05:01AM +0200, Philipp
Überbacher wrote:
Sorry to post this
twice, but I think the mail got truncated.
Hi Fons, I'm a fool to even try to answer this question.
But I couldn't resist...
Let's suppose we have two sounds A and B,
and sound B has been measured as being twice as loud as A,
by somebody. In order to be able to say that, that person needs
some kind of reference measurement unit, the equivalent of a
measurement stick. That unit has to satisfy two requirements.
It has to be big enough, so that people can agree some difference
is being measured, and it has to be small enough, so that a multiples
of that unit fit into a realistic range. There is a requirement of
maximum
precision (the smallest value we can measure), and a requirement of
minimum precision. The question is, what kind of measurement stick
is being used by that person.
First of all, we can assume that the length of that stick will be
depend
on the range of possible input values that we observe, and that we
want
to measure. If we want to measure the size of a road, we will
probably
use kilometers, instead of meters. In the same way, when our ears want
to measure the amplitude of a sound, our ears will use smaller or
bigger
units, depending on the ranges observed. What are the ranges we
observe?
Let's assume that humans are perfect, and observe everything that we
can observe with SPL meters. We could do a statistical investigation
on a number of people, and make charts of everything they hear.
In these charts we would see what frequencies they are exposed to,
and what the minimum and maximum SPL's are for that frequencies.
After more analyses, we would have one chart that could be
representative for most people.
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 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 ? From that chart we could get an estimate of the
size of the
measurement
unit. Frequencies with with bigger SPL variations would be measured
with bigger units, and visa versa. And from this we could deduce what
the minimum precision is for a certain frequency, when we say it is
twice
as loud. To satisfy the requirement of maximum precision, we should
take into account the smallest observable differences for every
frequency
in the spectrum.
now you can kill me :-)
Greetings,
Lieven