Posted 25 November 2009 - 11:00 PM
Posted 26 November 2009 - 09:33 AM
The recorder also should have adequate shielding against RF or EM Fields to prevent false positives. Beyond that hard to say without knowing the specs on a particular make / model you may be interested in.
And forget the little digital voice recorders. I have not seen one yet that meets minimum specs. (Zoom H2 is the cheapest digital I've seen to date.)
Posted 26 November 2009 - 12:13 PM
I've heard audio from a Zoom left out over night and you can literally hear everything. Bugs buzzing by, leaves rustling in the wind.
What would you recommend for a good digital audio recorder for use in the outdoors? Without spending a 1000 dollars of course.
Posted 26 November 2009 - 05:16 PM
And another I have tested and found satisfactory is the Fostex FR2, but it's a bit more money, listing at $1,199.
Posted 09 February 2010 - 12:42 PM
Posted 09 February 2010 - 05:17 PM
Now to address the points in the above posting
First I am aware of AA-EVP. They have changed their name but not their standards. I won't go into it here, but I have crossed them on several occassions and can show engineering flaws in many of their ideas regarding various techniques they use. Just because they claim certain things does not make it so, especially since some run contrary to proven scientific facts. But to each his own. If they choose to beleive in fantasy, so be it. Rather than argue against them I will however throw a few things out here regarding cheap recorders.
You WILL get more EVPs with a cheap recorder, exactly as Adventureseeker says. Trouble is cheap recorders are also prone to everything else as well, and as such it is impossible to separate the valid EVP from the false artifact that the recorder creates. In the end if you captured something that sounds like a classA EVP, but due to inadequate shielding inside ther ecorder, you can't say with absolute certainty it isn't stray RF interference, what have you gained? Under those conditions how reliable is your evidence? Sure you can get EVPs on cheap recorders, but relaiable performance requires at least a step above simple voice recorders intended for taking notes or dictation.
Standards? These have been set by engineers and technicians who understand the methods of digital recording. I personally conducted a series of tests using audio analysis equipment to arrive at what I have found to be the minimum levels needed to avoid possible problems from alaising, intermodulation distortion, conversion errors, and other artifacts that are present to some degree in all digital recordings. This is the type of work I do. The equipment used for this type of evaluation is expensive, and not needed for paranormal research so I doubt many people here access to it. What I have done is put some common recorders under tests to see how they perform and their immunity to problems that could cause false positives. The standards are based on the results of those tests. I wonder if AA-EVP has ever attempted anything like that?
1 - 96 KBPS sample rate. This is high enough that aliasing is minimized across the audio spectrum. True you can use 48 KBPS, however using a spectrum analyzer at the higher frequencies above 10 kHz some distortion can be detected. Thus I recommend 96 KBPS or higher.
2 - 24 Bit wide A to D conversion. That is the number of bits used in the recording process. Most cheap recorders use 16, better recorders use 24. It allows for finer definition in the conversion process. Without going into all the math, an analogy can be made to digital cameras. Many cell phone cameras use a 1.3 mpix CCD imager. Most decent digital cameras these days are 6 mpix or more. Both take pictures, but compare the clarity of the higher pixel count to the lower. Same applies to A to D conversion. More bits are better, resulting in a more accurate conversion process.
3 - Stereo recording. We have two ears, that allows us to hear depth. We can determine direction and the dual sound paths provide a clearer sound, easier to understand. To maintain that ability two channels are needed. That means two mics, two tracks, and stereo headphones. Sure you can use mono, but again why handicap yourself? Plus the dual channels serve as a redundency check. If you get an EVP it should appear in both channels. If it only appears in one, it is a red flag that maybe wht you got is a false artifact.
4 - Non-lossy recording. That means a recorder using an uncompressed WAV or similar format. MP3 or those recorders based on Linear Predictive Coding codecs are lossy. Without going into how they work, suffice it to say that in order to compress the audio certain "Uneeded" elements are discarded. But since we don't know what EXACTLY an EVP is and how it is generated, how can we say what is uneeded? Answer, we can't. So we keep everything, and for that you need a non-lossy format. Cheap voice recorders lossy formnats to save memory and keep costs down.
You are right regarding "cleaning" Digitral cleaning alters the original and should NEVER be done. Again, the way around that is a clean high gain input on your recorder in the record opertaion. That pushes the S/N ratio higher resulting in a clearer sound from the beginning. One can get high gain even in some cheap recorders, but keep in mind that the use of low impedence differential input can give you much better common mode rejection thus lowering the possibility of outside interference. Trouble is differential input generally has lower gain. This is remedied by additional amplification stages which increases cost. Thus once again you get what you pay for.
Finally you mention spending thousands. Yes you can do that if you demand the absolute best available. But it's not necessary. You can meet the specs above with the H2 or comparable recorder. Those can be had online for around $160, That is more, but not a lot more than the $50 spent on something that doesn't meet specs. It's just a matter of the quality and reliability of the evidence you want to obtain.
This is a short summary of a few issues, I have outlined things in more detail on my website if anyone cares to read a more indepth report covering equipment selection. Click my sig below.
0 user(s) are reading this topic
0 members, 0 guests, 0 anonymous users