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Ultrasonic everything

Well, not everything, obviously.
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A recently bought a bat detector, which makes the chirrups of bats audible by modulating them against another high frequency.

It is, of course, effective at detecting bats. But it also opens up a whole new ultrasonic world. A quartz watch whistles, a mechanical watch becomes a rhythm-and-bell orchestra, and a walk in the woods becomes a cacophony of crushed leaves and previously unheard animalogenic noises.

Most mobile telephones and many other gadgets have microphones which will pick up ultrasonics quite well. I suggest an app for such devices, to translate ultrasonics into the audio range, opening up a an entirely new (if largely useless) world to, ah, the world.

MaxwellBuchanan, Aug 18 2010

Bat Detector Kits http://www.google.c...urce=og&sa=N&tab=wi
Many available. [csea, Aug 19 2010]

http://en.wikipedia...ki/Beat_(acoustics) [hippo, Aug 19 2010]

Frequency of Bat Sonar http://hypertextboo...98/JuanCancel.shtml
[Wrongfellow, Aug 19 2010]

This might actually work http://en.wikipedia.org/wiki/Microphone
[21 Quest, Aug 20 2010]

Bat Detector http://en.wikipedia...#Bat_detector_types
[21 Quest, Aug 20 2010]

[link]






       It would take a bit more than just software. Maybe the microphone can reproduce ultrasonic frequencies, but the A-to-D converter it's attached to probably cuts off somewhere around 16kHz at best.   

       That said, a hearing aid which could do this would be a very interesting device. I'd certainly enjoy having a play with one.
Wrongfellow, Aug 18 2010
  

       I'm sure there's ultrasonic A/D's which you could use in digitally dropping stuff down a few octaves... might be ultrasonic microphones available.   

       I'm not sure how you're going to "modulate it against another HF sound" though.
FlyingToaster, Aug 18 2010
  

       Certainly there are - but I bet they aren't fitted as standard in mobile phones.   

       The fastest A-to-D converter I ever got to play with sampled at 40MHz. That's more than enough to reproduce a bat's sonar. It wouldn't have run for long from a phone battery though.   

       As for the modulation bit, that's easily done in software. It could be as simple as inverting the sign of every second block of N samples, followed by a simple low-pass filter. Something like a Nexus One has plenty of CPU grunt to do this kind of DSP in real time.
Wrongfellow, Aug 18 2010
  

       not useless in any way! Pair with a speaker and another mic for ultrasonic sonar to see in the dark!
Voice, Aug 18 2010
  

       //Most mobile telephones and many other gadgets have microphones which will pick up ultrasonics quite well.//   

       I strongly doubt this. Please provide reference. Most mobile phones use electret elements with FET impedance converters, and response drops off rapidly over 16-20 kHz.   

       I have also used an ultrasonic hetrodyne "bat detector," based on a cheap piezo transducer and a CMOS 20xx quad inverter biased for use as oscillator/ mixer / amplifier.
csea, Aug 19 2010
  

       What Chuck said. Bone until you can cite a reliable source for your technology claims. I'm not saying they can't, but I've not heard anything that indicates they can.
21 Quest, Aug 19 2010
  

       //but I've not heard anything that indicates they can//
Maybe the frequency was too high for you.
coprocephalous, Aug 19 2010
  

       [Useless segway] What gets me is that I can hear bats. Click click as they fly around. I've told people and generally I get funny looks, but I can hear (at least part of) the sonar used by several bat species from where I live. [/UW]   

       ...Anyhoo, can the ultrasonic transducers used for thickness testing and the like be used? How about the ultrasonic transducers used for stockpile height or feedbin/hopper level? Or maybe depth sounder/fish finder transducers? I suppose I just want this to work, sounds fun...
Custardguts, Aug 19 2010
  

       I'd tend to agree with [csea]'s observation, it wasn't long ago that mobile phones couldn't get any reasonable sample rate at all while recording.   

       Subsonic frequencies would be present though. So with a bit of filtering and up-shifting an elephant detector might be quite feasible, but before getting the soldering iron out I'll make some garlic bread as I've read its pretty good at flushing poisonous metals from the system.
bigsleep, Aug 19 2010
  

       //Useless segway// - (sp. "segue", unless you're suggesting that Dean Kamen's transportation device is useless, which would be right)

I'm wondering if you'd be able to hear ultrasonic sound by playing a similar frequency sound and listening for the 'beats' between the two frequencies (see link) - e.g. if there's an ultrasonic sound at 25kHz, could I play a 20kHz tone and hear 'beats' at 5kHz? I think probably not, as the beat frequency is that of the modulated volume and you still wouldn't be able to hear the underlying frequencies, but I'm not sure.
hippo, Aug 19 2010
  

       You need some kind of non-linearity for heterodyning to work. Normal air is too linear, at least at normal amplitudes.   

       It's quite possible that [Custardguts] can hear bats, if he's got decent hearing. The low end of their frequency range overlaps with the high end of ours (link).
Wrongfellow, Aug 19 2010
  

       //Bone until you can cite a reliable source for your technology claims.//   

       Point taken, alas. I hereby bone myself. However, I should point out that bats, at least, are bloody loud at 15- 30kHz, so a cellphone mike would probably pick up enough.   

       //Click click as they fly around. I've told people and generally I get funny looks// A lot depends on the species of bat and what it's doing. Most people pre-middle-age can hear at least some of the noise made by many bat species. But what you can hear is only a teeny fraction of what they're saying.
MaxwellBuchanan, Aug 20 2010
  

       From what I read in Wikipedia (linky), this idea might actually have some merit:   

       //Nearly all cell-phone, computer, PDA and headset microphones are electret types. They are used in many applications, from high-quality recording and lavalier use to built-in microphones in small sound recording devices and telephones. Though electret microphones were once considered low quality, the best ones can now rival traditional condenser microphones in every respect and can even offer the long-term stability and ultra-flat response needed for a measurement microphone//   

       Fishbone removed. Staying neutral because I still don't know how relevant that data is to this application. I posted another link to a Wiki article about types of bat detectors. Maybe someone smarter than me can cross-reference the capabilities of an electret microphone with some of the bat detectors and find some commonality?
21 Quest, Aug 20 2010
  

       WP: "Bats emit calls from about 12 kHz to 160 kHz, but the upper frequencies in this range are rapidly absorbed in air and many bat detectors are limited to around 15 kHz to 125 kHz at best."   

       Given that electrets, especially the smaller mobile phone type go up to 20K then I guess this is feasible after all. Then you're limited to the sampling rate and modern phones can probably go up to the full 44kHz. If you search around your desktop you probably can't find anything that goes above 48kHz, and its unlikely that common software will support much more including mobile phone OS's etc.   

       To recap: the maximum recordable frequency on mobile phones is 22kHz so the low end of a bat call should be audible with suitable software. Specialised bat phones would needed to hear the whole thing.
bigsleep, Aug 20 2010
  

       Very very cool.   

       //long-term stability and ultra-flat response needed for a measurement microphone//   

       Yes, but those in phones are typically only flat up to about 20kHz at the top end. The guy who posted this idea is an idiot.
MaxwellBuchanan, Aug 22 2010
  
      
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