| From: | "Arno R. Lehmann" <arlehma@***.NET> |
|---|---|
| Subject: | Re: Ultrasound vision |
| Date: | Thu, 4 Feb 1999 22:23:41 +0200 |
>On Wed, 3 Feb 1999, Arno R. Lehmann wrote:
>
>> Or, IOW, just tell me how long sound waves typically are...
>> somehow I think that they can't be that long, but I could be wrong...
>
> IIRC, the speed of sound in air is 340 m/s. In water it's faster,
>but for the life of me I can't remember the actual number, but we're
>talking about an ultrasound sight here, not sonar, so it doesn't matter
>too much.
> For a wavelength calculation, you would take the distance that the
>wave travels in a second (340m) and divide by the number of cycles per
>second (Hertz) of the frequency. Something on the order of 700 Hz (which
>is within the human vocal/hearing range) has a wavelength of 0.4857 m or
>roughly 49 cm.
> An ultrasound system would have a frequency that was much higher,
>in the inaudible range (or else everyone would be able to hear your
>gunsight), and would have commensurately smaller wavelengths.
Ok, thanks... these 340 m were what was missing here... it was somwhat
late when I wrote that mail ;-)
ok, let's see... say, 30.000 Hz for frequency (hearing range goes up to
about 20kHz) gives wave lengths of about 1 cm, right?
That should equal a resolution of .5 cm, IIRC (if not it's 2 cm), which
would be sufficient for gun aiming, I guess. For an integration which
uses a whole wave only 1/30.000 s would be necessary, then, which is
not terribly long, I think.
In water, things would be really different, but then again, sonar is
already there, we don't have to re-invent it, you're right :-)
Anyway, I still don't see why integration times would be a problem as
long as my ideas are correct... if not, I would like some more input on
this... I guess I'm just inventing something to annoy my players...
Arno
--
Arno Lehmann
arlehma@***.net http://www.geocities.com/TheTropics/Cabana/5274/
arno@*******.ast.uct.ac.za http://pinguin.ast.uct.ac.za
