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!

On 10 Mar 2007 05:18:34 -0800, in sci.electronics.design
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!
http://pw1.netcom.com/~t-rex/BatDetector.html may work


martin

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!


Interesting.

The mixing process requires a non-linear device, which, for your
purposes, I suspect the air is not. I've often considered, but never
attempted, a similar mixing process using human ears (connected and
intact, of course), since ears are quite non-linear. Ears won't work as
mixers in your case since, at least for most adults, they are
insensitive to ultrasonic frequencies (as well as to intelligent
political analysis, it seems).

The suggested bat detector is far more promising.

Chuck

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On 10 Mar 2007 05:18:34 -0800,
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!

Why worry about it... His yard, his pets, his life...

OK,

Take a microphone with a frequency response 30Khz, and an amplifer.
Monitor the amp's output with a scope. bg

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?)

On Mar 11, 1:19 am, PeterD wrote:
On 10 Mar 2007 05:18:34 -0800,
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!

Why worry about it... His yard, his pets, his life...

OK,

Take a microphone with a frequency response 30Khz, and an amplifer.
Monitor the amp's output with a scope. bg

Agree. Even a bog standard electret for $1 will do it - probably
wouldn't even need an amplifier......if you want to get sophisticated,
put it in the end of a piece of 30mm plastic pipe - voila, directional
microphone....

The alternative is you are just being paranoid......but I know you
know that anyway...

Andrew VK3BFA.

Andrew VK3BFA wrote:


Take a microphone with a frequency response 30Khz, and an amplifer.
Monitor the amp's output with a scope. bg

Agree. Even a bog standard electret for $1 will do it - probably
wouldn't even need an amplifier......if you want to get sophisticated,
put it in the end of a piece of 30mm plastic pipe - voila, directional
microphone....

The alternative is you are just being paranoid......but I know you
know that anyway...

Andrew VK3BFA.


Hello Andrew,

Do you know of any freq response curves on the web for the garden
variety electrets? I've looked and haven't found any.

Thanks,

Chuck NT3G

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Do you know of any freq response curves on the web for the garden
variety electrets? I've looked and haven't found any.
====================
I found an Archer packaged (for Tandy) cat no 270-092B Electret
Condenser Mike Element in its original Package, complete with response
curve.
From 30 - 3000 Hz the response is flat.
From 3000 Hz to 5000 Hz the response increases by approx 10 dB.
From 5000 - 9000 Hz the response drops such that it is back to its
original level at 9000 Hz .Above that freq the response drops.
Response curve is not extended beyond 12000 Hz



Frank GM0CSZ / KN6WH

Try using a Motorola Peizo Tweeter. I think some are spec'd into
ultrasonic range.

Highland Ham wrote:

Do you know of any freq response curves on the web for the garden
variety electrets? I've looked and haven't found any.

====================
I found an Archer packaged (for Tandy) cat no 270-092B Electret
Condenser Mike Element in its original Package, complete with response
curve.
From 30 - 3000 Hz the response is flat.
From 3000 Hz to 5000 Hz the response increases by approx 10 dB.
From 5000 - 9000 Hz the response drops such that it is back to its
original level at 9000 Hz .Above that freq the response drops.
Response curve is not extended beyond 12000 Hz



Frank GM0CSZ / KN6WH


--
Joe Leikhim K4SAT
"The RFI-EMI-GUY"©

"Treason doth never prosper: what's the reason?
For if it prosper, none dare call it treason."

"Follow The Money" ;-P

On 10 Mar 2007 05:18:34 -0800, 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!

Suspend a thin shaving razor blade between two pieces of dental floss and put
your ear close to the blade. Watch the razor vibrate.