ESD and ESamp?

[grendal]

My friend and I were talking about listening to tones beyond the audible hearing threshold. Before my friend left, he mentioned, something called ESD and ESAmp that convert EMF and RF waves into the audible tone. I've been looking about google for hours and I've not seen any reference to them. Does anyone know that ESD and ESAmps are? I won't be seeing him for about a week and a half so I won't be able to ask him. I wondered if someone here might know.

Thanks in advance.

 

[carbonzit]

Hmm; given that one of the first links to pop up in a Google search is this one, which is a paranormal web site, I'd suspect that this is just more junk science (aka bunkum, pseudoscience, crappola, BS), of which there's a ton out there.

There's nothing magical or mystical about converting high-frequency signals to lower ones; that's how we're able to hear whale "songs", for instance. But the idea of pulling such signals out of the ether and making some kind of sense out of them ... well, you be the judge.

Critical thinking, folks, critical thinking.

 

[grendal]

Yeah that's what pops up for me too, but thats not what we were talking about. Every time storms specifically thunderstorms roll in, my dogs go ballistic. We were wondering why. I hear nothing, but they go crazy. Wanted to listen in for fun and haha chuckles, maybe even record it. What ever makes them go ballistic is what we're looking for, not spirits or anything like that. If it works for what ever it is, might be able to apply it to the local cove. We allegedly have dolphins, but I've never seen them, might be able to hear them if the ESD and ESAmp stuff can be tuned, but first need to figure out what it is.

 

[carbonzit]

Well, what makes them go ballistic is thunder and lightning, right? Why do you think you need to investigate "ether waves" or whatever to determine that? Do you expect to be able to tap into some kind of signal that they can perceive but not us?

If you record a lightning storm, you'll get a lot of spiky noise. You could try some kind of frequency conversion on it, I suppose, but I'm not sure you'd get anything interesting out of it, other than a lot of crackles, pops and such.

 

[tcmtech]

I think that a large part of it comes from the fact that many animals have hearing ranges that go above and below our 20 - 20,000 Hz average range.

Dogs can hear things we consider ultra sonic and as most animals they are more sensitive to the subsonic frequency's as well. Thunderstorms being loaded with high level ULF sound are easy to hear and can be rather disturbing to some domesticated animals.

One simple but fairly effective trick to hear those frequency's is to record them with a typical analog tape recorder that has been modified to pick up ULF sound and then play it back at a much faster tape speed so that it shifts the ULF frequency up into our hearing range. Thunder storms played back at faster rates becomes loud pops and clicks loaded with growling and chirping. The same works for ultrasonic recordings but in reverse. It gets recorded at a fast tape speed and then played back at a much slower one to bring it down into a range we can identify with.

 

[carbonzit]

Hmm, maybe I should take that back, then, about listening to frequency-shifted lightning not being interesting.

So apart from using sped-up tape recorders, are there any good electronic ways to do this (frequency conversion to audio range)? Heterodyning? any simple circuits out there?

So, lessee, to try to answer my own question:

A guy would need a VFO, check. And a mixer to produce beat frequencies with the original signal. And then an adjustable low-pass filter to remove the unwanted (upper) sideband signal. Sound correct so far?

The VFO would need to be somehow linked to the filter. How, I have no idea ...

v0.1: Don't really need a VFO and adjustable filter. Just an oscillator and filter, both of which are fixed but can be switched to different frequencies if one wants to explore different spectra.

Can anyone come up with a simple circuit that would do this?

 

[grendal]

I've seen something on it, in elektor magazine. Not sure wich one...