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#1
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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! |
#3
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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 ----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
#4
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#5
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#6
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On a sunny day (10 Mar 2007 05:18:34 -0800) it happened
wrote in .com: Hi chaps, Google 'bat detector'. |
#7
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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 |
#8
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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? |
#9
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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 |
#10
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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 |
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