One thing to bear in mind is that the perception of proximity is far easier to achieve with (fairly
rapidly) moving sources. If you get the changing patterns of simulated early reflections right, the
ear/brain will focus on the consistent cues (early reflections) and tend to ignore the inconsistent
ones like the direct to reverb ratio. Unfortunately, once the sound stops moving, the direct to
reverb ratio becomes more consistent, so....
However, with any loudspeaker based system, you are continually battling against the loudspeaker
radius (a.k.a. "reverberation radius" or "critical distance") problem - that is, the sound from a
loudspeaker (or loudspeakers) always tries to sound like it is coming from not less than the
distance of the loudspeaker, simply because (one of) the strongest distance cue is the ratio of
direct to reverberant sound. It's easier if you have a very dead room and the soundscape you are
trying to reproduce has noticeably more reverberation, since you can then get the
direct-to-reverberant ratio more closely right. Not that it's easier with WFS or HOA to get some of
the other cues right, such as wavefront curvature and this helps greatly - but is not a panacea.
There are only two ways (at present) that I am aware of in which you can, even theoretically, do it
- short of physically having moving loudspeakers. The first is individually headtracked binaural
synthesis over headphones, the other is the use of steerable spots of sound produced by crossing,
modulated ultrasonic beams - a bit like Holophonics <http://www.holosonics.com/> Acoustic Spotlights
but with more widely spread transducers, so that the demodulation only occurs where the beams cross.
Dave
On 30/05/2012 14:10, Augustine Leudar wrote:
This is also something I've been wondering about and trying to achieve in
sound installations. A fly landed on a microphone once when I was recording
in the jungle and when played back it sort of worked - sort of - but I do
think the cognitive visual factors (the sound installation was in a large
indoor jungle at the eden project) helped enormously with believability -
but anyone listening carefully would have heard a fly about 1 foot high !
I am told Wavefiled synthesis what you decribe , though haven't heard it
myelf - I will be building a small WFS setup this summer - quite looking
forward to hearing it. Another low tech solution which is really crude but
would probably work would be to have a tiny speaker on an invisible string
and pulley system pulling it round the room. We are considering introducing
fireflies to the sound installation this year and that was one idea that
crossed my mind.... Realistic proximity is a tricky thing to achieve !
FA
This touches on something i've wondered for a while now. Discrete surround
always sounds as though it's in a fixed ring to me. Sounds are always the
same
distance away. I've experianced that with binaural recordings as well. Is
there
a surround sound method that will reproduce actual depth enough so that you
could track the movment of a fly in a room? I'd love a system where i
could hear
a fly moving towards my face, veering off a few inches away, moving at a
diagonal to 5' away then zig-zaging back and around my head.
Would the lack of a visual component effect that strongly? I can still
locate a
fly without seeing it.
Can ambisonics do that with a good mic for the W?
Thanks,
Bearcat
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