s30880f@puukko.hut.fi (Marko Winblad) (01/13/90)
Hello there! I'm working on a project that should finally yield some kind of mobility aid for the blind. Over the last few weeks I have noticed that there is quite a lot of research being done on this subject, but these separate research groups don't know about each other. Even in Finland there are three groups (including mine), that quite recently learnt about each other. Officially my project doesn't belong to the joint European COST-project (#219?) on handicapped aids, but I have already got some information from the participants (Semiconductor laboratory/Technical Research Center of Finland). If YOU know someone who is also working on this kind of project - handicapped aids, electronic travel aids etc. - would you please ask that person to contact me via e-mail (or snail mail). I don't plan to steal anybody's secrets (or give up mine :), but we could exchange at least some general information, like references. Co-operation is still power, isn't it? Marko Winblad I s30880f@puukko.hut.fi (=130.233.224.33) Helsinki University of Technology I Tel. +358 0 451 2313 (job) Laboratory of Applied Electronics I 468 2364 (home) Otakaari 5, SF-02150 Espoo, Finland I Error .signature 3: Stolen layout
jkh@meepmeep.pcs.com (Jordan K. Hubbard) (02/06/90)
You'll probably want to talk to the Smith-Kettlewell Institute
of Visual Research in San Francisco. They've done a lot of interesting
things for the blind. One of the things they had that impressed me
(at least in concept, the implementation still had a few rought edges) by
its general simplicity was a system for indicating the room
numbers by broadcasting a recording of the room number ("one-oh-three...
one-oh-three..one-oh-three..") over an IR led mounted above the door
frame. A small receiver would pick up the broadcasted signal and
decode it (presumably into an earphone). It seems that a simple
unit could be built to announce just about everything ("Emergency
exit..", "Mens room..", "Harry's bar".. etc) using an IR led (TIL32 or
equiv), a small ROM and some glue logic. I think the SKIVS system
used tape, but nowadays you can get at least 20 seconds of reasonable
quality sound into one ROM, using compression [and the current high capacity
of ROMs]. The biggest problem to overcome is getting the receiver and/or
transmitter to work reliably given the various forms of light interference
and angles of reflection involved.
This brings me to my main question, however..
Here in Munich, during the summer evenings, we have lots of Bats
that congregate over the river to munch on winged insects and other
savory morsels. I've often sat watching them swooping around, wishing
that I could somehow eavesdrop on their guidance signals and see how and
when they "ping" their targets. Questions:
1. What is the frequency range and average amplitude of bat radar?
2. What sort of microphone(s) would be best? If bat radar is fairly
low amplitude, should I build a parabolic mike? How does one properly
design a parabolic dish for a given freqency range? I probably don't
want to go for omnidirectional sensitivity anyway, since that would
make it impossible to track a single bat diving after an insect.
3. What sort of frequency converter circuitry would I need?
The ideal setup would be a small box containing the electronics and
batteries with a jack for a pair of headphones to monitor the
down-shifted signals and a jack for some sort of pistol-grip mounted
mike that I could point at areas of interest.
Sorry if these questions are a bit simplistic, I'm afraid my expertise
lies more in software than hardware.
Any and all help would be much appreciated. I'd be happy to forward
any information I get to other interested parties (I suspect that it's
a somewhat esoteric area of interest, however).
Jordan Hubbard
jkh@meepmeep.pcs.com
Munich, West Germany
PCS Computer Systeme GmbH, Munich, West Germany
UUCP: pyramid!pcsbst!jkh jkh@meepmeep.pcs.com
EUNET: unido!pcsbst!jkh
ARPA: jkh@violet.berkeley.edu or hubbard@decwrl.dec.comdkazdan@cwsys2.cwru.edu (David Kazdan) (02/07/90)
Question was posted about eavesdropping on bat sonar... No, I don't know a lot about it except that it is mostly <40 KHz and fairly high amplitude. What I do know about (that you may be interested in) is that one of Harold Edgerton's Harvard students (Doc was at MIT right up until his death a month or so ago) did a stroboscopic film of bats that included a real-time soundtrack. I think that he did it by slowing the tape at the same rate as the image, so pitch and speed came down together; he must have had a very wide-bandwidth tape recorder. There may have been some heterodyning involved. At any rate, several of the Strobe Alley workers of that era are still around the lab, and a letter to them may prove fruitful (fruit bats and all...all right, weak pun. But did you see the article on vampire bats' cooperative behavior? Current Scientific American...a fascinoma). 73, --David
wordy@cup.portal.com (Steven K Roberts) (02/08/90)
Also check into the book "Tuning in to Nature" by, I believe, Phillip Callahan. Steve Roberts Nomadic Research Labs
marks@mgse.UUCP (Mark Seiffert) (02/09/90)
In article <1990Feb5.162926.3877@pcsbst.pcs.com> jkh@meepmeep.pcs.com (Jordan K. Hubbard) writes: >Here in Munich, during the summer evenings, we have lots of Bats >that congregate over the river to munch on winged insects and other >savory morsels. I've often sat watching them swooping around, wishing >that I could somehow eavesdrop on their guidance signals and see how and >when they "ping" their targets. Questions: > >1. What is the frequency range and average amplitude of bat radar? > >2. What sort of microphone(s) would be best? If bat radar is fairly > low amplitude, should I build a parabolic mike? How does one properly > design a parabolic dish for a given freqency range? I probably don't > want to go for omnidirectional sensitivity anyway, since that would > make it impossible to track a single bat diving after an insect. > >3. What sort of frequency converter circuitry would I need? > >The ideal setup would be a small box containing the electronics and >batteries with a jack for a pair of headphones to monitor the >down-shifted signals and a jack for some sort of pistol-grip mounted >mike that I could point at areas of interest. > > Jordan Hubbard > jkh@meepmeep.pcs.com > Munich, West Germany > PCS Computer Systeme GmbH, Munich, West Germany > UUCP: pyramid!pcsbst!jkh jkh@meepmeep.pcs.com > EUNET: unido!pcsbst!jkh > ARPA: jkh@violet.berkeley.edu or hubbard@decwrl.dec.com This appeared here sometime ago, hope it helps. From rex!ukma!tut.cis.ohio-state.edu!cs.utexas.edu!oakhill!charlie Wed May 10 16:52:49 CDT 1989 Article 557 of sci.electronics: Path: mgse!rex!ukma!tut.cis.ohio-state.edu!cs.utexas.edu!oakhill!charlie >From: charlie@oakhill.UUCP (Charlie Thompson) Newsgroups: rec.ham-radio,sci.electronics Subject: BATRADIO Keywords: BATS Message-ID: <2000@radio.oakhill.UUCP> Date: 24 Apr 89 15:25:04 GMT Organization: Motorola Inc. Austin, Tx Lines: 40 Xref: mgse rec.ham-radio:1056 sci.electronics:557 Posted: Mon Apr 24 10:25:04 1989 Status: RO This weekend I decided to scrounge through my junkbox and build a BATRADIO. I took a 25 Khz narrowband ultrasonic transducer and preamp'd it and passed the amplified signal to a homebrew direct conversion 25 KHz receiver. The receiver was a homebrew mixer and a Wavetek 111B (B as in battery powered). The output of the mixer was lowpass filtered and sent a jambox for listening. Austin has a rather unique downtown bat population that lives under the Congress street bridge. At sundown the bats begin stirring and then, all at once, about 500,000 bats stop hanging around and start flying in one giant cloud. Bazzare. The BATRADIO worked great and I learned a lot about bat transmissions. Later, after the bats had left the bridge, I drove home and set up the BATRADIO again. I detected one lone bat, somewhere in the dark chirping away. Bat transmissions are FM/AM. That is, they are swept pulses, like a chirp...which is what they sound like when you downconvert to the 'human band'. Sometimes the chirping is fast ... sometimes slow. The bat on my street was chirping slowly until a car drove by and it suddenly went to double the chip rate...presumably it had 'locked on' to the car. When the car went away the bat resumed chirping at the slower rate. From what I could tell the bats must have a 'deviation' of 5 to 10 KHz. Since my receiver was only about 2 KHz wide at 25 KHz I couldn't know exactly what the deviation was. The transducer that I used was resonant so it was not very useful to tune my local oscillator since the sensitivity dropped off abruptly outside the range of the transducer's center frequency. Anyway, it was an educational experience... and the best VLF'ing I've done in a long time! Happy bat hunting. -Charlie Thompson WB4HVD Austin, Texas -- Mark Seiffert, Metairie, LA. uucp: rex!mgse!marks bitnet: marks%mgse@REX.CS.TULANE.EDU internet: marks%mgse@rex.cs.tulane.edu