I don't think that the parabolic reflectors will help due to resolution;
they will focus sound from a large distant area over the smaller area of the
sensor. You probably need a "shotgun" mic made from several long lengths of
tube bundled together in front of the sensor.

Don't use one length since the tubes will reject frequencies related to
their length unless you can figure out what length matches the frequency you
are looking for. In that case, the tubes will act as a filter as well as a
directional element.

I've had very good results with long soda straws cut to lengths that vary by
about a half inch.

The phased array strikes me as the only way to increase sensitivity without
giving up resolution. I can see a huge stack of soda straws with another
stack of sensors behind them. However... there was an article in Nuts &
Volts Magazine... one of the regular columns... about increasing sensor
resolution buy using two sensors and comparing the outputs. Not sure if it
applies. Will try to find if interested.

Great project! Let me know how it goes.

James Newton, webmaster http://get.to/techref
jamesnewton@geocities.com <mailto:jamesnewton@geocities.com>
1-619-652-0593 phone


> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Matt Bennett
> Sent: Wednesday, June 23, 1999 7:46 AM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: PIC based imaging sonar
>
>
> I've built a PIC based (16F84 and 16C71) sonar that, along with a computer
> can produce an image- I've got a picture and some details here:
>
> <http://www.hazmat.com/~mjb/projects/picsonar/>
>
> I wanted to get some feedback and maybe enlist some help in the effort, so
> take a look and tell me what you think.  It is far from complete,
<SNIP>
> My azimith resolution is poor, due to the transducers that I'm
> using,  I've
> found much more focused transducers, but they are much larger and far more
> expensive.  I fully realize that size and gain are coupled, but I'm hoping
> I can figure out a way to increase gain (and correspondingly the
> resolution)
> without resorting to a far more expensive transducer.  A couple of the
> ideas I have been toying with are parabolic reflectors and phased
> arrays of
> transducers (actually just multiple transducers placed the proper
> number of
> wavelengths apart, driven in paralell).
>
> So, please take a look, and let me know what you think.
>
> Thanks,
> Matt Bennett
>
> --
> Matt Bennett
> mjb@arlut.utexas.edu
> 512-835-3867
>