[Noisebridge-discuss] Speakers and amplified sound at NB

[LinkReincarnate]

That high pitch noise is a subharmonic and can easily be tuned out.  We
should totally hack together another pan and scan device though.  I have a
couple of servos, an ultrasonic emitter array, and some time.  I'll be at
noisebridge shortly blasting sound at things.  Also if I have upset anyone
that was not my intention.  I am passionate when i defend my side of an
arguement but i can just as easily defend the other side...
On May 29, 2013 1:02 PM, "Gopiballava Flaherty" <gopiballava at gmail.com>
wrote:

>
> On May 29, 2013, at 12:49 PM, LinkReincarnate <linkreincarnate at gmail.com>
> wrote:
>
> > The optimal solution would be to build a set of ultrasonic emitter
> arrays to beam sound only to people who  want to hear it without headphones.
>
> I thought that an array like that would be really cool, but when we got
> one it turned out to not work nearly as well as you'd hope:
>
> a) It only works optimally in an anechoic chamber. When the in-phase
> superposed waves hit your ears, they mix to form audible sound.
> Unfortunately, when they hit the slightly echoic surfaces around you, the
> result is audible sound. The room we were in was a lot smaller than NB, so
> maybe the echoed audible sound would be quiet enough to not be an issue in
> a large enough room
>
> b) There was extremely high pitched sound that was sometimes audible. I
> don't know if the unit we had wasn't high enough frequency, or if the wave
> superposition sometimes created annoying high pitch noise.
>
> c) I think this was a construction artifact: you could hear some audible
> sound right by the unit. I believe that the grill or other structures would
> produce some diffuse vibrations right next to the unit that would superpose
> right there.
>
> I don't actually know much of the technical specs of the unit we had. It
> was built by DaimlerChrystler in ~2004 as part of a research project. We
> had it mounted on a pan-tilt unit and pointed it at people to directly
> deliver text messages without interrupting people around them. The overhead
> projector system worked much better for that.
>
> Thanks,
>
> gopi.
>
>
>
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>
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