Don, I believe this paper bears more attention than a quick skim as it makes a number of fundamental & interesting points:
- In signal processing, in band-limited systems there is a limit to how precisely we can
simultaneously measure both time & frequency i.e there is an uncertainty! These experiments show that in a number of people tested that they could beat this uncertainty, some by 10 fold "We study human ability to simultaneously judge the frequency and the timing of a sound. Our subjects often exceeded the uncertainty limit, sometimes by more than tenfold, mostly through remarkable timing acuity."
- So what? Well "When applied to filters, the result is that one cannot achieve high temporal resolution and frequency resolution at the same time; a concrete example are the resolution issues of the short-time Fourier transform – if one uses a wide window, one achieves good frequency resolution at the cost of temporal resolution, while a narrow window has the opposite trade-off."
- OK, so what again? "Our results establish a lower bound for the nonlinearity and complexity of the algorithms employed by our brains in parsing transient sounds, rule out simple "linear filter" models of early auditory processing, and highlight timing acuity as a central feature in auditory object processing."
- Eh? "In many applications such as speech recognition or audio compression (e.g. MP3 [18]), the first computational stage consists of generating from the source sound small sonogram snippets, which become the input to latter stages. Our data suggest this is not a faithful description of early steps in auditory transduction and processing, which appear to preserve much more accurate information about the timing and phase of sound components than about their intensity"
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so the suggestion is that being very accurate in recreating the frequency/amplitude of a signal is actually the wrong focus if this model of the perception of hearing is correct. I've highlighted this as it is fundamentally counter to what is still the current focus in audio development & as Jack says & I say myself, without an accurate understanding of how we hear what we hear, we are perhaps chasing accuracy where it's not needed & ignoring the real issues.
I barely skimmed the paper. It appears to target time delay, and it has been shown that our ability to locate objects uses pretty small time delays (on the order of a few us IIRC). For components, the only place I see it being a significant issue is speakers, and that is part of what led to the effort to time-align the wavefroonts from speakers (and my love of planar speakers, but that's another story). Phase shift and group delay is easily measured over frequency for electronics, a little harder for speakers, but should certainly be measurable. I think it's another of those things we can measure but usually don't. Consumers seem to have a hard time undestanding some of the basic specs that are provided, and there seems to be little incentive to provide more (and a lot of reasons to not, including cost and time of testing, educating customers about why it matters, etc.) Seems to me most specs are there because they are required, either by regulations or because "everybody does them". The few added specs usually crop up when the company feels there is a marketing advantage (which may have nothing to do with actual audible advantage).
I do not know how much delay we can sense in say a musical selection if the highs and lows are delayed differently in time by a small amount. I would be curious if the paper (or any paper) has addressed that. I suspect it would alter the image somewhat.
My 0.000001 cents (microcent) - Don