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. _______________________________________________ Linux-audio-dev mailing list [email protected] http://lists.linuxaudio.org/listinfo/linux-audio-dev
