[Csnd] 3d audio: turning an audio source away from the listener

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[Csnd] 3d audio: turning an audio source away from the listener

Jeanette C.
Hey hey,
I'd like to change the direction of an audio source in a 3d or stereo context.
Assuming that the source is small enough so that the position doesn't need to
change at all. Is there an approximation of how to change the sound to give
the impression of a source turning?

Supposition: one could modulate the phase accordingly. But isn't there a
filtering effect as well? If that is a part, an approximation would help.
Linear would do. :)

Any other cues that might help the listener to form the image of a change in
direction?

Best wishes,

Jeanette

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Re: [Csnd] 3d audio: turning an audio source away from the listener

zappfinger
You might want to take the Doppler effect into account, so changing the
pitch slightly depending on the direction.
And also filtering. I guess moving away not only makes the cound less
loud, but also loses low frequencies...

Richard

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Re: [Csnd] 3d audio: turning an audio source away from the listener

Jeanette C.
Sep 16 2018, Richard has written:

> You might want to take the Doppler effect into account, so changing the pitch
> slightly depending on the direction.
thank you, I used that as well.
> And also filtering. I guess moving away not only makes the cound less loud,
> but also loses low frequencies...
Hm, I would suspect that the signal looses high frequencies. But in
which way? Linear, quadratic/cubic. Is there a limit, factors that come
into it?
...

Best wishes,

Jeanette

--
  * Website: http://juliencoder.de - for summer is a state of sound
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Re: [Csnd] 3d audio: turning an audio source away from the listener

Peter P.-2
In reply to this post by Jeanette C.
* Jeanette C. <[hidden email]> [2018-09-16 19:35]:
> Hey hey,
> I'd like to change the direction of an audio source in a 3d or stereo
> context. Assuming that the source is small enough so that the position
> doesn't need to change at all. Is there an approximation of how to change
> the sound to give the impression of a source turning?
I think the key here is to ask, as the directional sound source turns
away, what does it radiate to instead? Now if these are reflective
surfaces aka walls of a room, the reflections would get louder in
relation to the direct sound. This could be modelled. As reflections
mostly absorb higher frequencies more than lower ones these, this
filtering can be taken into account as well.
If the source turns away from the listener, rather than gets displaced, I
would consider the Doppler effect neglibile.

best, Peter

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Re: [Csnd] 3d audio: turning an audio source away from the listener

Jeanette C.
Sep 16 2018, Peter P. has written:
...
> Now if these are reflective
> surfaces aka walls of a room, the reflections would get louder in
> relation to the direct sound. This could be modelled. As reflections
> mostly absorb higher frequencies more than lower ones these, this
> filtering can be taken into account as well.
...
Hi Peter,
thanks for your reply. I guess this effect could be modelled if I worked
from scratch. Considering that I might need realtime execution, I'd
rather go with existing models and for some aspects approximation. I
haven't yet seen any spatial opcode or even a stereo one, which directly
models a directed sound source. As far as I'm aware all sources in these
cases are unidirectional point sources. Maybe I'm making too much of the
filtering anyway and its effect is also to be dismissed? Otherwise: what
cutoff frequency curve am I looking at?

Again thanks for your input and the new angle.

Best wishes,

Jeanette

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  * Website: http://juliencoder.de - for summer is a state of sound
  * SoundCloud: https://soundcloud.com/jeanette_c
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Re: [Csnd] 3d audio: turning an audio source away from the listener

Peter P.-2
* Jeanette C. <[hidden email]> [2018-09-16 23:45]:

> Sep 16 2018, Peter P. has written:
> ...
> > Now if these are reflective
> > surfaces aka walls of a room, the reflections would get louder in
> > relation to the direct sound. This could be modelled. As reflections
> > mostly absorb higher frequencies more than lower ones these, this
> > filtering can be taken into account as well.
> ...
> Hi Peter,
> thanks for your reply. I guess this effect could be modelled if I worked
> from scratch. Considering that I might need realtime execution, I'd
> rather go with existing models and for some aspects approximation.
Possibly just dial up the volume of an early reflections reverb as the
source is supposed to "turn away", and reduce the dry sound. Means,
adjust the dry/wet balance of a reverb. Possibly in combination with
some slight panning of the reverb returns to give the impression that
something twists.

> I
> haven't yet seen any spatial opcode or even a stereo one, which directly
> models a directed sound source.
Not in CS, but I think spat~ allows to divide a mono sound source into a
directional and omnidirectional part, which are then processed
separately if I am not mistaken.

>As far as I'm aware all sources in these
> cases are unidirectional point sources. Maybe I'm making too much of the
> filtering anyway and its effect is also to be dismissed? Otherwise: what
> cutoff frequency curve am I looking at?
Depends on the absorption coefficient of the material the walls are
supposed to be made of. Ignore this and go by ear perhaps?

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