[LAD] Attenuation of sounds in 3D space

Ralf Mardorf ralf.mardorf at alice-dsl.net
Thu Jul 29 17:43:36 UTC 2010


On Thu, 2010-07-29 at 19:32 +0200, Ralf Mardorf wrote:
> On Thu, 2010-07-29 at 10:00 -0700, Fernando Lopez-Lezcano wrote:
> > On Thu, 2010-07-29 at 16:14 +0200, Ralf Mardorf wrote:
> > > On Thu, 2010-07-29 at 17:01 +0200, JohnLM wrote:
> > > > On 2010.07.29. 15:20, Gene Heskett wrote:
> > > > > On Thursday, July 29, 2010 08:52:04 am Jörn Nettingsmeier did opine:
> > > > >
> > > > >> john,
> > > > >>
> > > > >> On 07/29/2010 02:35 PM, JohnLM wrote:
> > > > >>> So from what I can understand, if I apply doppler effect, distance
> > > > >>> attenuation and other pre-process filters to a mono input and then
> > > > >>> push it through the panner plugin I get fairly correct representation
> > > > >>> of sound in 3D space. Right?
> > > > >>
> > > > >> depending on what you mean by "fairly correct", "representation", and
> > > > >> "3D space" :-D
> > > > >>
> > > > >> doppler would come into play only if you change the distance of the
> > > > >> sound, not when you move it on the sphere, as the distance remains
> > > > >> constant.
> > > > >
> > > > > This use of 'doppler' I would call incorrect, because the doppler shift is
> > > > > a shift in the apparent frequency of the sound rising at it approaches, and
> > > > > decreasing as it leaves.  I'm sure you have a term for what you mean, but
> > > > > doppler isn't it.  That police officers radar gun measures your speed by
> > > > > listening to the echo from your vehicle, and comparing it to the signal its
> > > > > sending, which to simplify, results in a beat frequency which is exactly
> > > > > your speed if approaching or departing exactly to or from the radar guns
> > > > > position.  That is why it is often called doppler radar&  the weather guys
> > > > > us it also.  Because they don't stand directly in front of you to take a
> > > > > reading, there is some small vector error in your favor.
> > > > >
> > > > >...
> > > > >
> > > > > That is why we call it the square law.  The only way to get that back is to
> > > > > make the receptor itself 4 times bigger.  But while I have observed that
> > > > > there are quite wide variations in ears, I have not seen an individual with
> > > > > expandable ears (yet) :)
> > > > >
> > > > >> when you hand-craft distance cues, you should not expect wonders for
> > > > >> sounds originating inside your sphere of speakers. travelling through
> > > > >> the center quickly can be made to work, though.
> > > > 
> > > > I am fairly sure 'doppler' *is* what I meant.
> > > 
> > > You notice a Doppler effect? So your speakers are far apart from each
> > > other, while you are moving very fast from one speaker to the other?
> > > Nothing else is called the Doppler effect.
> > > There might be a sound similar or equal to a Doppler effect, but of
> > > course using this term is bad.
> > 
> > You don't understand. 
> > 
> > The previous posters are talking about _simulating_ moving sound
> > sources. So you, the listener, stay in place, and the composer or sound
> > artist is crafting cues for you that will simulate the movement of
> > sources around you. If those sources move towards or away from you (ie:
> > have a radial component of the velocity vector) then you should simulate
> > the doppler effect they would have if they were real objects. It is a
> > very powerful cue. 
> > 
> > So, yes, it is doppler and no, use of the term is not bad or incorrect. 
> > 
> > -- Fernando
> > 
> > PS: for example, read:
> >   https://ccrma.stanford.edu/courses/220a-fall-2001/chowning.pdf
> >   http://www.dxarts.washington.edu/courses/567/08WIN/chowning.pdf
> > 
> > 
> 
> Sorry, you could be right, if you aren't talking about 'realworld'
> recordings, but about movements by virtual sources.
> 
> E.g. the 'virtual ambulance' is driving very fast ... not a recording,
> but a virtual setup.
> 
> Interesting :).
> 
> Ralf

PS to the German speaking people (perhaps understandable on English
too):

Imagine that you don't record the "TatüTata" of the police car, but you
have got a sampled sound of this noise and you wish to move it by using
a pan pot.

We would miss the Doppler effect :D.





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