Ah yes, the proverbial point source. Never heard one of them, never want to
- a true point source would imply an infinite power density to output
anything which would, in turn, imply infinite energy density which would
imply infinite density and ...... oh dear, we seem to have a black hole and
all we were trying to do was play a goose recording :-)
Dave
On 13 April 2015 at 12:59, Peter Lennox <[email protected]> wrote:
> The distance (technically, "range" - from perceiver to source- -) problem
> encountered in "giant geese: (John Leonard's ambisonic recording of
> close-miked geese played over a large, <30m radius rig) was the disparity
> in subtended angles produced by the decorrelation across any image with
> non-neglible ASW (apparent source width) in combination with a perceptiual
> constancy for speaker distance in any non-anechoic performance site.
> As Dave says, we had fun with several examples of 'blown up' images - a
> giant toilet (with high-flush cistern), a VW (mine) that approached
> plausibly enough, then as it traversed the speaker array - whose radius was
> significantly greater than the mic-source distance - the VW stretched and
> became huge, about 15metres long and high as a house - then it departed,
> plausibly enough.
>
> My students have encountered the same when trying to reproduce a
> "Mousetrap" game (a thing with rolling marbles that travel along little
> troughs, drop to the next level and so on) in an auditorium - change the
> display radius, and the sound of the speed of rolling and the change of
> angle seriously don't match.
>
> So, one can't just treat things as 'point sources' (what is one of those,
> exactly?) and movement has to take into account the display radius.
>
> Still, a giant toilet flushing was fun to behold.
>
> regards
> ppl
> Dr. Peter Lennox
> Senior Fellow of the Higher Education Academy
> Senior Lecturer in Perception
> College of Arts
> University of Derby
>
> Tel: 01332 593155
> ________________________________________
> From: Sursound [[email protected]] On Behalf Of Dave Malham [
> [email protected]]
> Sent: 12 April 2015 09:12
> To: Surround Sound discussion group
> Subject: Re: [Sursound] Boids for Ambisonic Panning
>
> Hi Ricky,
> Boids has been around for a long time and I'm certain it's been
> used quite a few times in electroacoustic compositions - in fact, I seem to
> remember one of our students on the Music Technology course here at York
> doing so. Trouble is, I'm darned if I can remember his or her name (which
> will be no surprise to anyone who's been on that course - my apologies to
> the person concerned if they are reading this :-). Your best bet would be
> to look through the Proceedings of the ICMC from around '87 and maybe the
> Computer Music Journal.
>
> I'm not sure what you mean by "...difficult to scale in terms of
> distance". Are you referring to the mapping of the notional distances in
> the boid simulation to the things which we use perceptually to deduce the
> distance of a sound source? That's opening up an interesting can of worms!
> Do a search in the archives for "giant geese" to see the fun we had talking
> (arguing) about it last time. A lot will depend on wether the sound sources
> are "familiar" or not - we can easily tell that a thunder storm (or a jet)
> is
> distant or nearby because we are familiar with them as "perceptual objects"
> and can construe them within the acoustic space we are listening in but
> with constructed sounds that we are not familiar with we are stuck with
> "immediate" (and to some extent, unreliable) cues like direct to
> reverberant ratios, the pattern of early reflections, HF rolloff and maybe
> distortion (loud sounds have distortion which increases with distance). If
> he's currently on the list, I suspect Peter Lennox will jump in here and
> tell me I've got it all wrong :-).
>
> Anyway, I'm sure much/all of this is old news for you but I had to have
> something to occupy a Sunday morning whilst waiting for the croissants to
> warm up ....
>
> All the best....
>
> Dave
>
>
>
> On 11 April 2015 at 22:05, Ricky Graham <[email protected]> wrote:
>
> > Hello,
> >
> > I use the boids algorithm to pan materials around a space. The Cartesian
> > output number range per boid in space is difficult to scale in terms of
> > distance; azimuth seems to be fairly intuitive and sounds correct to my
> > ears.
> >
> > Do any of you have any similar experiences / advice on how best to
> > approach distance when using boids?
> >
> > Best,
> >
> > Ricky
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>
> --
>
> As of 1st October 2012, I have retired from the University.
>
> These are my own views and may or may not be shared by the University
>
> Dave Malham
> Honorary Fellow, Department of Music
> The University of York
> York YO10 5DD
> UK
>
> 'Ambisonics - Component Imaging for Audio'
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As of 1st October 2012, I have retired from the University.
These are my own views and may or may not be shared by the University
Dave Malham
Honorary Fellow, Department of Music
The University of York
York YO10 5DD
UK
'Ambisonics - Component Imaging for Audio'
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