Detecting Ultrasound
 

Detecting Ultrasound
 

John Smith I wrote:
Scott wrote:
clifto wrote:
Stace MacGuyver wrote:
Suspend a thin shaving razor blade between two pieces of dental floss
and put
your ear close to the blade. Watch the razor vibrate.

That's pretty cool, MacGuyver. Does the razor blade do anything?

It cuts off your ear if you get too close ;)

Be better if you could use it as an electric razor ...

Replace the dental floss with Litz wire and attach ends to 110 VAC.

Wait. Maybe not. Considering how many stations you can pick up with a
razor-blade radio, that would probably interfere with vital communications
all throughout the spectrum. What's the resonant frequency of a whisker?

--
Martians drive SUVs! http://oregonmag.com/MarsWarm307.html

Detecting Ultrasound
 

On Mar 10, 5:18 am, wrote:
Hi chaps,

I suspect a neighbour of a friend of mine is using an ultrasonic bird-
scarer to frighten off his pets. The man concerned won´t admit to it,
but there are times when his dog and two cats just seem to get
suddenly very distressed and hypermanic for no apparent reason. I`d
like to at least eliminate this possibility before considering any
others. So the question is, what´s the simplest way to detect
ultrasound? My web research leads me to believe the area of interest
is between 20 and 30khz. Most common bird scarers warble between these
two limits which are of course above the range of human hearing. I´ve
acquired an ultrasonic transducer that transmits on 41khz. If I couple
this up to a wien-bridge oscillator trimmed to the same frequency, I
figure I ought to be able to hear a warble if indeed this guy is using
a birdscarer, because the difference between 41khz and 20khz-30khz
will be audible to me. Is this feasible to "air mix" the two
frequencies in this simple way and hear a result, or is something more
complicated required?
Thanks!

You need your detector to be low Q since you don't know the offending
frequency. Some of these fancy sound cards do 196kHz sampling. A
piezo microphone with amp into the sound card might do the trick.

Also, as other have suggest, the bat detector.

Detecting Ultrasound
 

Detecting Ultrasound
 

John Smith I wrote:
wrote:

...

Do you really want to hear it, or have a "field strength
indicator"/locater?

Why not just a mike capable of "hearing" the ultrasonic freqs in
question--feeding an opamp and meter?

Pointing the mike around should lead you into the correct direction and
following the meter reading should lead you to the source(s).

Possibly can substitute a light or even a led in series with a pot and
use a visual indication of strength ...

JS



Come to think of it, wouldn't take much more to square up the sine wave
out of the opam and drop a cmos decade-divider onto that output of the
opamp and feed an ear phone with the dividers output--30,000 becomes
3,000 hz--easily "hear-able!"

JS

Detecting Ultrasound
 

On 2007-03-10, John Smith I wrote:
John Smith I wrote:
wrote:

...

Do you really want to hear it, or have a "field strength
indicator"/locater?

Why not just a mike capable of "hearing" the ultrasonic freqs in
question--feeding an opamp and meter?

Pointing the mike around should lead you into the correct direction and
following the meter reading should lead you to the source(s).

Possibly can substitute a light or even a led in series with a pot and
use a visual indication of strength ...

JS



Come to think of it, wouldn't take much more to square up the sine wave
out of the opam and drop a cmos decade-divider onto that output of the
opamp and feed an ear phone with the dividers output--30,000 becomes
3,000 hz--easily "hear-able!"

only if theres no other sound present in the mic signal.

and it will give no indication of signal amplitude.

Detecting Ultrasound
 

On Sat, 10 Mar 2007 09:19:25 -0500, PeterD wrote:
Why worry about it... His yard, his pets, his life...

I *think* what the OP is worried about is that his friends' pets are being
scared off by his freinds' neighbor.

While I hate to discourage anyone from building something electronic, I do
have to ask: what will one do if they learn that a bird-scarer *is* in
use? Best of my knowledge, they aren't illegal.

If a bird-scarer works on dogs, then I find the details quite interesting.
May have to work up a mobile version. Loose dogs allowed to roam a
neighborhood are a serious safety issue for cyclists. (and I wonder if
that's why the neighbor in question is trying to scare them off?)

Detecting Ultrasound
 

clifto wrote:

John Smith I wrote:
Scott wrote:
clifto wrote:
Stace MacGuyver wrote:
Suspend a thin shaving razor blade between two pieces of dental floss
and put
your ear close to the blade. Watch the razor vibrate.

That's pretty cool, MacGuyver. Does the razor blade do anything?

It cuts off your ear if you get too close ;)

Be better if you could use it as an electric razor ...

Replace the dental floss with Litz wire and attach ends to 110 VAC.

Wait. Maybe not. Considering how many stations you can pick up with a
razor-blade radio, that would probably interfere with vital communications
all throughout the spectrum. What's the resonant frequency of a whisker?


They don't make the blue blades anymore.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

Detecting Ultrasound
 

Michael A. Terrell wrote:
clifto wrote:
John Smith I wrote:
Scott wrote:
clifto wrote:
Stace MacGuyver wrote:
Suspend a thin shaving razor blade between two pieces of dental floss
and put
your ear close to the blade. Watch the razor vibrate.

That's pretty cool, MacGuyver. Does the razor blade do anything?

It cuts off your ear if you get too close ;)

Be better if you could use it as an electric razor ...

Replace the dental floss with Litz wire and attach ends to 110 VAC.

Wait. Maybe not. Considering how many stations you can pick up with a
razor-blade radio, that would probably interfere with vital communications
all throughout the spectrum. What's the resonant frequency of a whisker?


They don't make the blue blades anymore.

Do they make any other kind of thin shaving razor blades?

--
Martians drive SUVs! http://oregonmag.com/MarsWarm307.html

Detecting Ultrasound
 

clifto wrote:

Michael A. Terrell wrote:
clifto wrote:
John Smith I wrote:
Scott wrote:
clifto wrote:
Stace MacGuyver wrote:
Suspend a thin shaving razor blade between two pieces of dental floss
and put
your ear close to the blade. Watch the razor vibrate.

That's pretty cool, MacGuyver. Does the razor blade do anything?

It cuts off your ear if you get too close ;)

Be better if you could use it as an electric razor ...

Replace the dental floss with Litz wire and attach ends to 110 VAC.

Wait. Maybe not. Considering how many stations you can pick up with a
razor-blade radio, that would probably interfere with vital communications
all throughout the spectrum. What's the resonant frequency of a whisker?


They don't make the blue blades anymore.

Do they make any other kind of thin shaving razor blades?


Yes, but the blueing was what made a detector.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida