[sdiy] harmonics & vibrato - drums

[Grant Richter]

It does seem unlikely that an adaptive effect would apply in a feed forward
method over a relatively long time period.

People say dripping water is an irritation, and that would be nulled out by
a long term adaptive mechanism.

The actual method of hitting something in time, involves a very complex
mechanism of neural transmission of muscle impulses, muscle reaction and
corrective feedback.

It does seem more likely that there are simple limits to the time precision
of the whole muscle/nerve system, rather than being involved with an
auditory adaptive effect.

Always fun to speculate, and it takes a lot of wrong hypothesis to get a
keeper %^)

> From: Chris Stecker <cstecker at umich.edu>
> Organization: University of Michigan
> Reply-To: cstecker at umich.edu
> Date: Fri, 20 Dec 2002 15:02:04 -0500
> To: <synth-diy at dropmix.xs4all.nl>
> Subject: Re: [sdiy] harmonics & vibrato - drums
> 
> Grant (and interested list),
> 
> Although "masking" is not the term I would necessarily use (it has a more
> specific, but related, meaning), there are many examples of adaptation in the
> nervous system, including (as Mr. Gravenhorst noted) fatigue of sensory
> receptors, and also lateral inhibition (stimulated regions of the retina
> suppress activity in neighboring cells, producing "Mach bands" or bright
> lines next to black/white boundaries). There are higher-order adaptive
> phenomena at many later stages of neural processing, that adapt to more
> complex or abstract aspects of stimuli. Some of these produce observable
> effects like afterimages, and some are more subtle or immediate. In general,
> adaptation helps to reduce the response to steady-state (continuous)
> stimulation, so that dynamic or transient stimuli are easier to detect. It's
> a bit like high-pass filtering or taking the derivative of any parameter
> you're interested in (across time, frequency, space, or whatever); changes
> become more noticeable, and the system's "dynamic range" is increased.
> 
> Lateral inhibition in the auditory system occurs between neighboring
> frequencies (as evidenced by "two-tone suppression" as well as various
> simultaneous masking phenomena), and also over time, as you suggested.
> Forward-masking (the reduced detectability of sounds following exposure to a
> masking--generally more intense--sound) is one example, and so is the
> precedence or Haas effect (reduced ability to localize or spatially segregate
> sounds following onsets). These phenomena and others are characterized by a
> limited duration of suppression (usually they have some measurable "recovery
> function").  [My specific research interest in this area is adaptation to the
> acoustics of rooms.]
> 
> What you're suggesting for drumming, however, is difficult for me to
> understand, primarily because we (I, especially) don't yet understand how
> rhythm, timing, and repetition are represented or processed in the brain.
> This theory would require a representation of intervals, whereby "units"
> representing particular intervals would fatique if repetitively stimulated.
> Jittering the intervals would spread activation around a small group of such
> units, causing less fatigue. It's not a totally unreasonable idea, and in
> fact at much shorter time scales (intervals around 5-10 ms) randomly varying
> the intervals (by a very large "jitter") reduces the strength of the
> precedence effect...but that's really a totally different time scale, a
> different perceptual dimension (space), and presumably a totally different
> type of mechanism (there is no precedence effect for intervals beyond 10 ms
> [clicks] to 50-100 ms [speech or music]). I don't know of any data suggesting
> that the perceptibility of sound is actually diminished by highly regular
> repetition, but it's possible that part of the "appeal" of less-quantized
> rhythm is in the "spreading around" of stimulation to more than one
> exact-interval processing "unit."
> 
> Here are two other possibilities I have in mind:
> 
> a) slight randomization sounds better because it sounds "human," and it sounds
> human because that's what we've been exposed to, listening to human drummers.
> (not that children raised by robots would think hard-quantization sounds
> "human," but...) Or maybe its a bit like the difference between
> photo-realistic painting and more expressive styles. (Or is it more like the
> difference between photorealistic painting and photography?)
> 
> b) slight randomization reduces the predictability of the beat. we like
> surprises, (because we pay attention to the derivatives?) so totally
> predictable rhythms sound "flat."  This is really just another way to frame
> your "crackpot" adaptation theory, but it does not depend on a low-level
> process that suppresses sound perception, per se. Rather, it hypothesizes the
> existence of fairly high-level perceptual adaptative mechanisms that track
> regularity in an analytic-synthetic, predictive, or change-oriented manner.
> 
> My money's on "a," as it seems simpler and in keeping with variability between
> listeners; some prefer "tight" (versus "sloppy") drummers, while others
> prefer "expressive" (versus "flat" or "robotic") ones. "b" appeals more to my
> views of neural computation, however, and is more aesthetically
> appealing/interesting, but that doesn't make it right (it's probably more
> testable though).
> 
> -Chris
> 
> 
> On Friday 20 December 2002 01:43 pm, Grant Richter wrote:
>>> Ok, this makes more sense.  But the question remains, is there a random
>>> factor or not?  If not, then why does doing a *slight* randomization
>>> (weighted in my case) sound better (um more "human") than a quantized
>>> track?
>> 
>> VERY Crackpot theory,
>> 
>> Neural systems have a masking factor. This prevents a stuck input from
>> tying up the whole net. Like when you stare at something and it leaves a
>> negative image in your eye. The negative image is the mask generated by the
>> neural system.
>> 
>> That may apply to time related items also, like when you are in a noisy
>> room and your ears adapt by "tuning" out the noise so you can hear better.
>> 
>> It may be that drummers instinctively play around the outside of the neural
>> "mask" time. If they hit perfectly on the beat every time, they eventually
>> couldn't hear themselves.
> 
>