Wow - thats real startrek material right there Dave ! I was letting my imagination wander in a similar area the other day and was wondering if the beating/harmonics caused by two beams of electromagnetic waves could somehow excite the air where their paths crossed causing a sound to eminate from that spot. Although it may sound a bit out there I found out from a PHD student that there some Russians doing something vaguely similar already except they are doing it the other way round - using ultrasound propogated in a liquid to create light :
http://www.myspace.com/video/12k-line/evelina-domnitch-dmitry-gelfand-quot-xenon-wind-quot-camera-lucida-dvd/7806818 On 30/05/2012, Dave Malham <dave.mal...@york.ac.uk> wrote: > 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 > _______________________________________________ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
