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From: Mark on 4 May 2008 09:37
On May 4, 4:17 am, "VelociChicken" <b...(a)yahoob.com> wrote:
> "Robert Adams" <robert.ad...(a)analog.com> wrote in message
>
> news:449e00a8-131c-4f7f-8373-4376ac671f55(a)c65g2000hsa.googlegroups.com...
>
>
>
>
>
> >I accidentally discovered something interesting, and thought I would
> > share it here.
>
> > Prepare a sound file with the following sequence of events.
>
> > 1) Pink noise, 10 seconds
>
> > 2) Filtered Pink noise with several notches in the frequency response
> > (moderate Q's, frequencies in the 200Hz to 5KHz range), 10 seconds
>
> > 3) Pink noise (no filtering), 10 seconds
>
> > You would think that 1) and 3) would sound the same. But what happens
> > is that your brain adjusts to the notched response in 2), and when you
> > play 3), you hear pronounced (and very annoying) peaks where the
> > notches used to be.
>
> > This is not one of those "subtle" effects that only audiophiles can
> > hear; it's such an extreme effect that you are tempted to think the
> > experiment is rigged somehow.
>
> > If you insert a period of silence between 2 and 3, your brain will
> > eventually reset itself, but it takes more time than you might think.
>
> > One thing I would like to try is to insert "reset events" between 2
> > and 3, other than silence, and see if the "reset period" can be
> > shortened.
>
> > To be honest, I had always thought that people who objected to double-
> > blind ABX testing were a bit wacky. But now that I understand a bit
> > more about this memory effect, I must admit that I can see where it
> > might be difficult to accurately compare two different audio signals.
> > I also wonder how important frequency response really is, given that
> > your brain seems to just adapt to the average spectrum anyway.
>
> > I know this has appeared in the literature before, but I found it
> > quite surprising, and it's a very easy experiment to set up yourself.
>
> > Bob Adams
>
> Is this a physical cortical effect or is it the brain doing this sound
> persistence? hmmm
>
> I've been watching a development on this Japanese site, and it shows this
> 'illusion' for visual stimuli too.
> See here:  http://www.psy.ritsumei.ac.jp/~akitaoka/chcolore.html &http://www.ritsumei.ac.jp/kic/~akitaoka/warp-e.html
> Somewhere on there, I can't find right now gives a very good example of how
> size, and more vividly, colour can be affected by surrounding  colours and
> shapes.
>
> And we all know we have a persistence of vision, from those 'stare at a
> picture, then look at a blank wall' games - but I guess some people would
> find it quite scary that their ears can be fooled too!  : )
>
> VC- Hide quoted text -
>
> - Show quoted text -

crossposted interesting thread to
rec.audio.pro

Mark
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