On 07/24/2010 10:31 PM, [email protected] wrote: > On Sat, Jul 24, 2010 at 02:58:36PM +0200, lieven moors wrote: > > >> On 07/23/2010 10:23 PM, [email protected] wrote: >> >>> On Fri, Jul 23, 2010 at 06:42:11PM +0200, lieven moors wrote: >>> >>> >>> >>>> On 07/23/2010 06:29 PM, [email protected] wrote: >>>> >>>> >>>> >>>>> Transporting this to the audio domain, given two similar >>>>> sounds A and B with a B having a higher level than A, you >>>>> could adjust a third one X so it appears to be 'halfway' >>>>> between A and B. If you do this with A much smaller than >>>>> B, would you expect X to be close to 'half a loud as B' ? >>>>> >>>>> >>>>> >>>>> >>>> If A would be very close to silence, yes. >>>> >>>> >>> I'd be *very* surprised if that would turn out to be true. >>> >>> I bet that if B is A + 40 dB, X would turn out to be >>> close to A + 20 dB. And if B is A + 60 dB, X will be >>> close to A + 30 dB. In both cases A is very small >>> conpared to B (at most 1/10000 in power). >>> >>> Ciao, >>> >>> >>> >> Let's put it differently. If you only had sound B, and you >> were asked to position a similar sound X halfway between >> total silence, and the level of sound B, wouldn't that be the >> same as asking that sound X has half the loudness of sound >> B, or as asking that sound B has double the loudness of >> sound X? >> > So with e.g. A = B - 60 dB we could end up with X at > B - 30 dB (two steps of 30dB which are supposed to be > near equal subjectively), That is assuming that our experience of loudness corresponds to the continuous logarithmic scale with which we measure SPL's. I suspect that this is not the case. Our ears have minimum and maximum SPL values they can observe/tolerate, and I think that this range is the 'unconscious' reference for measurement of loudness. So we might have to adapt the 'steepness' of the logarithmic curve to that range. > while with A = silence we would > have X somewhere between -6 and -10 dB relative to B > (these are the extremes of common values for 'twice as > loud'). How low can A be before this inconsistency turns > up ? Or more important: how reliable is such an idea of > 'halfway' ? > I would say it's the only reliable thing in this context, because it's the very thing we want to measure. > The simple fact is that on a logarithmic scale the whole > concept of 'half' or 'double' is **meaningless**. That is > because such a scale depends on an arbitrary reference > value, and changing that value shifts the whole scale by > a constant amount without changing the underlying reality. > Two levels that are e.g. 10 and 20 on one scale (hence the > second is 'double' the first) could be as well be 80 and 90 > just by changing the reference value for the log scale. > Yes, but changing the base does change the underlying reality. > Of course half/double still makes sense in the original > domain. But if the perceptual scale is logarithmic, they > are perceived as a constant difference, not as a ratio. > I think we are aware of the original domain, in de sense we are approaching the limits of our hearing. What we interpret as half/double as loud depends on the position within that range.
regards, Lieven _______________________________________________ Linux-audio-dev mailing list [email protected] http://lists.linuxaudio.org/listinfo/linux-audio-dev
