Quote (Irwinjs22 @ Jan 3 2011 08:15pm)
I have personally experienced a ghost encounter, since then I have been extremely interested in this subject. As far as the tape recorders go, the human voice cannot speak in the white noise frequency that the voices are recorded, nor can we hear them. I did some research and I was unable to dig up any software that can allow someone to edit the frequency that the data is stored on but I guess that doesn't mean it doesn't exist. I think most believers have had a personal experience at one point in time or another.
Humans can generally hear between 20 and 20,000 Hz, and adults tend to lose the top 8-10 kHz of that spectrum, though those are very high pitches (like the 'ring tone' that only kids can hear) and are outside of the normal speaking range.
Now, in signal processing/sampling, you NEED to have a device that's sampling (i.e. taking measurements) at more than twice the nyquist frequency (highest frequency contained in the signal that you're sampling). So, for example, if the highest frequency of this "white noise" is 40 kHz, then you need to be sampling at at LEAST 80 kHz. So if the device used to record the sounds wasn't sampling fast enough, no program can possibly recover the data there.
There are matlab programs that you can quickly and easily write to do a fourier transform on a sound file to find out what frequencies are present in a signal, but again, a fourier transform won't detect frequences too high to have been recorded due to the nyquist frequency.