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 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.

On a sunny day (10 Mar 2007 05:18:34 -0800) it happened
wrote in
.com:

Hi chaps,

Google 'bat detector'.

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?

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

It cuts off your ear if you get too close



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?

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!

The obvious "detection" would be oscilloscope observation
of the amplified microphone signal. That's been mentioned.

Some commercial ultrasound detectors simply heterodyne
the ultrasonic range down to audible frequencies...good if
your hearing goes on up to the high end of human response.
Expensive as portable devices but easily genned up on the
average home workbench.

There are a couple of claims of outdoor advertising via sound
through using high-power ultrasound generators in pairs, one
modulated in amplitude the other unmodulated. The air acts
as the non-linear "mixer" and the claim is that such beams
of ultrasound can be focussed on particular locations. One
such company is located in San Diego, California, if memory
serves.

73, Len AF6AY

Scott wrote:
It cuts off your ear if you get too close



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?


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

JS