[LAD] twice as loud

[Ralf Mardorf]

On Thu, 2010-07-22 at 21:31 +0200, lieven moors wrote:
> On 07/21/2010 07:24 PM, Fons Adriaensen-2 wrote: 
> > 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 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 ? 
> 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.
> 
> >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

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.