Posted 07 December 2010 - 04:53 PM
Does anyone know if it then converts what is recorded in that range to a frequency humans can hear, or is that feature only useful when used with a program such as Audacity? Come to think of it, is the ability to record down to 15Hz even useful at all in the context of recording EVP's, or is just useless marketing hype?
Thanks in advance for any replies.
Posted 07 December 2010 - 09:02 PM
It is not clear if lower recording frequency sensitivity is helpful or harmful when it comes to obstensible EVP recordings. While it might capture something other recorders would not, one could also say that it extends the noise band from which you might hear yet more artifacts.
Posted 07 December 2010 - 10:46 PM
Plus there are some other considerations when dealing with infrasound below about 20 Hz when it comes to amplifier design. One of these is stability regarding bias on linear stages. Compensation must be made to keep those in their linear operating areas, and that becomes somewhat complex. Not saying they didn't do it, but if I were wanting to do infrasound work I would choose a DC amplifier which I knew was properly compensated. This one is an unknown in that regard.
One more thing regarding low frequencies and EVPs. These can easily be mistaken for vocalizations due to the fact that the duration most phonemes of speech also occur over time periods of 10 -30 msec. This is very close to the wavelength of infrasound and unless you are careful the two can be easily confused. I can see this as a cause for false positives.
You would also want provisions to display those frequencies on a scope or other visual means. Again keeping in mind most headsets won't respond that low unless you go with professional grade equipment.
All in all, from what I have seen of this recorder literature it appears to be mostly hype aimed at wanna be ghost hunters. It does some things besides the white noise that really aren't beneficial to an investigator. Better to put your money into a decent, simple recorder that meets specs for EVP work instead of paying extra for a lot of superfluous stuff.
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Posted 10 December 2010 - 10:56 AM
Now I would be impressed if a unit could pick up sub harmonic, or ultra sonic sounds and demux into the audible range. This can be done, but with lot's of $$ gear as you already know.
Posted 10 December 2010 - 11:14 AM
Posted 10 December 2010 - 01:00 PM
There actually is a limit to the frequencies for EVP. By definition, they are a voice phenomena, thus their limit is to the regions between approximately 100 - 3.5 kHz as this covers normal voice patterns.
That said it is also quite possible to pick up anomalous signals outside that range, however these would have to be considered something other than voice phenomena. Consider infrasound as an example. If a very low frequency such a 10 Hz for example were present it could modulate a higher frequency or even noise to simulate voice. The pulses of noise, 100 msec long would mimic the series of phonemes which comprise speech. That would be a very good source for pareidolia .
It would not be actual voice phenomena, but could easily fool one into thinking it was.
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