Re: "laser" microphone

In article <f0vln2$13v$1@xxxxxxxxxxxxxxxx>,
kludge@xxxxxxxxx (Scott Dorsey) wrote:

<genericaudioperson@xxxxxxxxxxx> wrote:
I think this was in Mix or EQ recently. I saw a picture in the
magazine. Something about air going through a tube and being scanned
by a laser. I would think the tube would produce non-linearities, and
would be susceptible to wind and air currents. It seems kind of
wild. Anybody know anything about "laser" microphones?

EM had a recent article. Basically, everybody wants a method of directly
digitizing at the microphone.

There are a bunch of proposed methods out there, including lasers bouncing
off of particles suspended in the air, and a laser system that measures
air density by seeing reflections when the optical impedance of the air
changes. Also we have the gadget with the laser reflected off a diaphragm
which strikes a plate with binary patterns cut in in; optical sensors on
the other side get a value proportional to the position which is proportional
to the displacement of the diaphragm.

I don't expect to see any of these soon. They all have various noise
and linearity issues so far. And they don't _really_ solve any actual
problems yet.
--scott

It's really not clear that there exists is a physical method for
directly measuring the individual particle velocities and air pressure
without using analog techniques to average the measurement over a large
population of molecules. The methods so far proposed all require
extensive DSP to reduce the inherent noise and uncertainty in the
measurement that grow as the scale is reduced to molecular dimensions.

State-of-the-art analog microphones are really pretty good, so are
current A/D converters. It will probably require an array of
transducers and plenty of DSP to get even that good.

-Jay
--
x------- Jay Kadis ------- x---- Jay's Attic Studio ------x
x Lecturer, Audio Engineer x Dexter Records x
x CCRMA, Stanford University x http://www.offbeats.com/ x
x---------- http://ccrma.stanford.edu/~jay/ ------------x
.

Relevant Pages

  • Re: The sound of a laser.
    ... what does a laser sound like? ... > I've read claim that a sufficiently powerful laser would ionise the air ... If the electrons in the "air" atoms are able to absorb light energy ... which may absorb or scatter the light as they drift into a continuous beam. ...
    (sci.optics)
  • Re: "laser" microphone
    ... Something about air going through a tube and being scanned ... Anybody know anything about "laser" microphones? ... C'est suisse, et tres, tres precis." ...
    (rec.audio.pro)
  • Re: The sound of a laser.
    ... > I've read claim that a sufficiently powerful laser would ionise the air ... mechanism for a laser to ionize air. ... crackling sound. ...
    (sci.optics)
  • Re: The sound of a laser.
    ... A few mJ is enough for air breakdown from a low f/ number focused Q-switched ... there is the sound of the caps discharging. ... >> At high instantaneous laser powers the ossilating electric field in ... >> electric field. ...
    (sci.optics)
  • Re: The sound of a laser.
    ... > I've read claim that a sufficiently powerful laser would ionise the air ... mechanism for a laser to ionize air. ... crackling sound. ...
    (sci.physics)