by Dave Sircom
Monday, April 13, 2009
Recording EVPs - Frequency Response Rate & Sample Rate
Most, if not all, of the technology we use in ghosthunting today had it's original purpose and function intended for an all together different use. Video cameras with infra-red certainly weren't invented with ghosthunters in mind nor were the thermal cameras such as those manufactured by FLIR but thank Heavens we've got them. The same can be said of digital audio recorders, electromagnetic field detectors and all the audio editing software available today.
Now, I have always found that my best Class "A" & "B" EVPs were captured with the use of low-end digital and analog recorders. Over the years I have collected thirteen different recorders from Radio Shack to SONY. And, I admit, I am a huge SONY fan. Whenever possible, I buy SONY. The problem I experienced with SONY digital recorders was not the hardware but with the software that would download it to the computer. I found it difficult to use and slow. That being said, one of my favorite recorders is the Panasonic DR60. This was the recorder pulled of the market by the manufacturer because the owners were complaining of the voices being recorded on messages when no one else was present. The DR60 is a great recorder if you can find one but you need to able to distinguish a real EVP from digital static. Of all the recorders I've used and seen others use, I have to say that Olympus would rank #1. Recently, I purchased an Olympus WS-210S as shown in the photo. I believe I paid around $89.00. It has proven to have been worth every penny. The main features for me are that it can be pulled in half and has a built in USB plug right there, no cord needed, records in stereo, has a great frequency response range and the software downloads the audio in better than acceptable speed utilyzing software already on your Windows system.
One question I am asked a lot is why did one recorder pick up an EVP but the other recorder located in the same room did not? Well, there can be several answers. The most probable explanation is that it "didn't hear it". This is because of the "frequency response" or the range of the recorders ability to hear sound. My Olympus WS-210S (pictured) has a frequency response rate begining at 150 Hz at the low end and a high end range up to 17,000 Hz in stereo XQ mode. This high end can be adjusted depending on the recording mode selected. Make sure to check yours so you always know the recording frequency range of your digital recoders.
Here's the range for the WS-210S:
Stereo XQ Mode: 150-17,000 Hz
Stereo HQ Mode: 150-15,000 Hz
Stereo SP Mode: 150-9,000 Hz
HQ Mode: 150-13,000 Hz
SP Mode: 150-7,000 Hz
LP Mode: 150-3,000 Hz
I also use an analog SONY M-529V microcassette recorder with an external microphone to keep out the internal "gear noise". But the frequency range is from 300 Hz to 4000 Hz. This means it cannot hear anything above 4000 Hz or below 300 Hz.
My next favorite analog recorder is the Radio Shack CTR-121 Desktop Cassette Recorder. The frequency response is 125 Hz to 6300 Hz and uses the high bias tapes.
EVPs can come from anywhere but my experience has been that I get the best results from the 150 Hz to 4000 Hz range but I don't want to miss a thing!
Another important consideration is the "Sample Rate" or as Wikipedia puts it:
Sampling rate
From Wikipedia, the free encyclopedia
"The sampling rate, sample rate, or sampling frequency defines the number of samples per second (or per other unit) taken from a continuous signal to make a discrete signal. For time-domain signals, it can be measured in hertz (Hz). The inverse of the sampling frequency is the sampling period or sampling interval, which is the time between samples.[1]
The concept of sampling frequency can only be applied to samplers in which samples are taken periodically. Some samplers may sample at a non-periodic rate.
The common notation for sampling frequency is fs which stands for frequency (subscript) sampled."
Simply stated, the more often (or the higher the sample rate) the more authentic or true to the original sound the recording of it is. Human speach usually ranges from 50 Hz to somewhere around 4000 Hz, but can higher. This is why telephones are desinged to go up to 8000Hz. It is generally accepted that 20,000 Hz is the maximum frequency that the human ear can detect. A dog, however, has a hearing of about 50 Hz to 45,000 Hz. So, in order to detect these human frequencies your sample rate must be, at least, double that amount. If you are attempting to capture EVPs at 4000Hz, you must have a minimum sample rate of over 8000 Hz. I usually set a sample rate of 44,000Hz because, as I said earlier, I like a wide frequency response rate of 150 Hz to 17,000 Hz and I don't want to miss a thing!
I hope this has shed a little light. And...
Please keep sending those questions and comments!