19 replies to this topic

[MAG-TEMP Mel-8704]

Yesterday I got my new digital Voice recorder
this is my other part of my ghosting hunting gear.
I be adding EVPs to local area ghost hunting in my Blog.
right now i'm trying figure out the voice activation in how to set up.
this just plugs in my pc to ubs port on my pc.
of course it uses Window audio player, but I wonder if ther is online software where i can load the file in to and for cleaning up and editing?
have any of you have trouble finding dead quit area to evps?

[Joven76]

I personally use Audacity, others use Wave Pad to listen and cut the EVP's from the audio clips, both are shareware...

As for finding a dead quiet area, that's near impossible to find... When ever you're conducting EVP work, you have to be aware of what's going on around you and any thing you hear like a car passing, a creek in the floor boards when you step on the floor, to a dog barking you have to tag... This way, when you go back and review, you won't mistake something else for a possible EVP... Also, make sure if you do catch anything that you analyze all possibilities it could be before you start researching paranormal abilities...

Good luck!!!

[MAG-TEMP Mel-8704]

yeah , there was a to get rid of back round noise,
just paranormorl emf readings you can't near any man made piower sources.

[PKsRevenge]

I have a zoom h4n but it never gets used, I have a free recorder app on my iphone that has picked up waaaayyyy more EVPs for some reason.

[afterlife]

Try adobe sound booth this is great way to clean up your EVPs. After downloading your EVPs into your computer all you do is drag & drop the file in sound booth and have fun! You can down load this from adobe for a trial period of 30 days at www.adobe.com/downloads.

[CaveRat2]

I have a zoom h4n but it never gets used, I have a free recorder app on my iphone that has picked up waaaayyyy more EVPs for some reason.

Of course you get more EVPs on a cheap recordeer. Trouble is they aren't really EVPs, rather simply artifacts caused by low sample rates, conversion errors, aliasing, IM distortion, and often RF interference from the poor shielding such recorders have.

I personally won't even consider a recording for EVP analysis unless it meets the following criterea:

1. Sample arte of 96 KBPS or greater

2. 24 bit A to D conversion

3. Stereo recording for redundency.

4. WAV or other uncompressed format, not CELP based. No MP3s. These can only be used to post a reduced quality EVP so someone can hear it, they should never be used for actual research.

Rec ordings made under these conditions don't need cleaned up, EVPs will be class A or they simply won't be there. About the only thing that needs done is some amplification to increase the volume level. EVPs digitally processed have been altered in content by the cleaning process (artifacts added or certain frequencies removed) and are useless for serious study.

[Kelli Chases Ghosts]

Of course you get more EVPs on a cheap recordeer. Trouble is they aren't really EVPs, rather simply artifacts caused by low sample rates, conversion errors, aliasing, IM distortion, and often RF interference from the poor shielding such recorders have.

Exactly. All my gear is RF tested at a 50 kW AM transmitter site and a 100 kW FM transmitter site BTW.

3. Stereo recording for redundency.

Just make sure it's true stereo and not JOINT stereo. Joint stereo will introduce artifacts from one channel to the other. of course, with the other parameters you've outlined, this is going to be the case anyway.

Rec ordings made under these conditions don't need cleaned up, EVPs will be class A or they simply won't be there. About the only thing that needs done is some amplification to increase the volume level. EVPs digitally processed have been altered in content by the cleaning process (artifacts added or certain frequencies removed) and are useless for serious study.

Exactly. I don't capture a lot of EVP, but the ones I do are very clear. "Cleaning up" a recording only serves to add more trash to the recording. If it has to be cleaned up to understand it, then it's not viable evidence IMO.

[Ten301]

I know there has been much talk on this site and others as to whether digital voice recorders are of high enough quality to reliably capture EVP's, and the suggestions that people purchase used cassette or reel-to-reel equipment instead. All good advice, I'm sure, but are there any digital voice recorders that can meet the specifications required? The fact is, bulky, older equipment is just not going to work for my situation, so I do need need something small and portable. I've read that the Zoom H2 does on it's highest quality setting, so I'm interested it it. Are there others?

[CaveRat2]

When I place the H2 as acceptable that doesn't by any means say that is the only recorder that meets specs. That only means that I tested it and found it to be the cheapest one at this time. I don't have the resources of Consumer Reports and haven't tested multiple brands for comparison, thus I don't make individual brand recommendations.

I would recommend that you spend some time checking various spec sheets from different manufacturers and compare those against the 4 criterea I posted. Any recorder that meets these is likely acceptable. If you find several that meet specs, then it becomes a matter of which one you prefer based on other features it offers, price, size, ease of use, etc. And remember too, it doesn't hurt if you exceed specs either. For instance, the H4 recorder will run circles around the H2. But of course it's more expensive. But why stop there? The Fostex FR2 which I have also tested exceeds specs in most areas. But at $1199 it should!!! Point is you get what you pay for as a rule.

[Tutthync73]

I dont know if this was asked one time on here or on another website but I am going to ask this now because I am wondering about this.

Its not possible for a digital notetaker to pick up radio frequencies is it?

Also.... can you get bleed through somehow on a digital recorder if you erase and then record again over a period of time?

[APGBryan]

Of course you get more EVPs on a cheap recordeer. Trouble is they aren't really EVPs, rather simply artifacts caused by low sample rates, conversion errors, aliasing, IM distortion, and often RF interference from the poor shielding such recorders have.

I personally won't even consider a recording for EVP analysis unless it meets the following criterea:

1. Sample arte of 96 KBPS or greater

2. 24 bit A to D conversion

3. Stereo recording for redundency.

4. WAV or other uncompressed format, not CELP based. No MP3s. These can only be used to post a reduced quality EVP so someone can hear it, they should never be used for actual research.

I'm curious... why do you consider only a digital recorder that records at a sample rate of 96 kbos or greater acceptable? According to the Nyquist-Shannon sampling theorem the perfect reconstruction of a signal is possible when the sampling frequency is greater than twice the maximum frequency of the sound being sampled. Since our audio range is from 12 hz to 20 khz, according to the theorem, perfect reconstruction of the sound is possible at a 40 kbps sample rate (44.1 khz is standard).

[CaveRat2]

Of course you get more EVPs on a cheap recordeer. Trouble is they aren't really EVPs, rather simply artifacts caused by low sample rates, conversion errors, aliasing, IM distortion, and often RF interference from the poor shielding such recorders have.

I personally won't even consider a recording for EVP analysis unless it meets the following criterea:

1. Sample arte of 96 KBPS or greater

2. 24 bit A to D conversion

3. Stereo recording for redundency.

4. WAV or other uncompressed format, not CELP based. No MP3s. These can only be used to post a reduced quality EVP so someone can hear it, they should never be used for actual research.

I'm curious... why do you consider only a digital recorder that records at a sample rate of 96 kbos or greater acceptable? According to the Nyquist-Shannon sampling theorem the perfect reconstruction of a signal is possible when the sampling frequency is greater than twice the maximum frequency of the sound being sampled. Since our audio range is from 12 hz to 20 khz, according to the theorem, perfect reconstruction of the sound is possible at a 40 kbps sample rate (44.1 khz is standard).

The reason I have set this as a standard is because we don't really know what or how an EVP is created. The Nyquist point must as you suggest be at least twice the highest frequency present. However this only applies to a sine wave. To reproduce a square wave without distortion requires the capability to reproduce all harmonics to infinity. Of course that is an impossibility, so for audio applications most accept what is refered to as the pseudo square wave. This is simply the first three harmonics, beyond that the level of distortion becomes acceptable.

Using this criterea the third harmonic of 8 kHz is 24 kHz. The Nyquist point to reproduce 24 kHz is 48 kHz, thus the limitation of 44.1 is somewhat less than 8 kHz. Acceptable for most applications to be sure, but remember we don't know whether EVP follows general audio rules. It may turn out that something beyond 8 kHz is a factor in EVP work. (Just a hypothesis). By raising the sample rate to 96 kHz, it becomes possible to capture audio up to 16 kHz using the same criterea. Thus the third harmonic is captured over much more of the audio spectrum without the high distortion levels occurring in the upper regions. And if in fact something is present there, we capture it too.

Admittedly some of this is theoretical, there may be no reason to push frequency respons above the lower normal voice band frequency. But since we are doing research it is better to capture everything including something you don't need than to capture only a portion and miss something significant. 96 KBPS was chosen as a reasonable compromise between the low sample rates which clearly are insufficient even to capture most voice, and a sample rate of several hundred KBPS which, while optimum, is likely beyond what most could afford. Research may at some point prove a need to go higher, but for now 96 KBPS seems sufficient.

another reason to go higher is that it allows more detailed analysis. While sampling at 2 times the highest frequency is sufficient for simply listening, for research purposes and display on spectrum analyzers a sample rate of 10 times is often advised.

In the end it is how seriously you want to study an EVP. If your only interested in What does it say?, then probably lower sample rates would suffice. But if you intend to do serious analysis, then you need more accurate conversions.

[APGBryan]

Of course you get more EVPs on a cheap recordeer. Trouble is they aren't really EVPs, rather simply artifacts caused by low sample rates, conversion errors, aliasing, IM distortion, and often RF interference from the poor shielding such recorders have.

I personally won't even consider a recording for EVP analysis unless it meets the following criterea:

1. Sample arte of 96 KBPS or greater

2. 24 bit A to D conversion

3. Stereo recording for redundency.

4. WAV or other uncompressed format, not CELP based. No MP3s. These can only be used to post a reduced quality EVP so someone can hear it, they should never be used for actual research.

I'm curious... why do you consider only a digital recorder that records at a sample rate of 96 kbos or greater acceptable? According to the Nyquist-Shannon sampling theorem the perfect reconstruction of a signal is possible when the sampling frequency is greater than twice the maximum frequency of the sound being sampled. Since our audio range is from 12 hz to 20 khz, according to the theorem, perfect reconstruction of the sound is possible at a 40 kbps sample rate (44.1 khz is standard).

The reason I have set this as a standard is because we don't really know what or how an EVP is created. The Nyquist point must as you suggest be at least twice the highest frequency present. However this only applies to a sine wave. To reproduce a square wave without distortion requires the capability to reproduce all harmonics to infinity. Of course that is an impossibility, so for audio applications most accept what is refered to as the pseudo square wave. This is simply the first three harmonics, beyond that the level of distortion becomes acceptable.

Using this criterea the third harmonic of 8 kHz is 24 kHz. The Nyquist point to reproduce 24 kHz is 48 kHz, thus the limitation of 44.1 is somewhat less than 8 kHz. Acceptable for most applications to be sure, but remember we don't know whether EVP follows general audio rules. It may turn out that something beyond 8 kHz is a factor in EVP work. (Just a hypothesis). By raising the sample rate to 96 kHz, it becomes possible to capture audio up to 16 kHz using the same criterea. Thus the third harmonic is captured over much more of the audio spectrum without the high distortion levels occurring in the upper regions. And if in fact something is present there, we capture it too.

Admittedly some of this is theoretical, there may be no reason to push frequency respons above the lower normal voice band frequency. But since we are doing research it is better to capture everything including something you don't need than to capture only a portion and miss something significant. 96 KBPS was chosen as a reasonable compromise between the low sample rates which clearly are insufficient even to capture most voice, and a sample rate of several hundred KBPS which, while optimum, is likely beyond what most could afford. Research may at some point prove a need to go higher, but for now 96 KBPS seems sufficient.

another reason to go higher is that it allows more detailed analysis. While sampling at 2 times the highest frequency is sufficient for simply listening, for research purposes and display on spectrum analyzers a sample rate of 10 times is often advised.

In the end it is how seriously you want to study an EVP. If your only interested in What does it say?, then probably lower sample rates would suffice. But if you intend to do serious analysis, then you need more accurate conversions.

That is very informative and I appreciate the exhaustive reply. I understand what you are saying regarding not knowing the elements of the evp, etc. I had never really considered this, but I was under the impression that you had set those standards to eliminate the possibility of false positives. If one wanted to be confident that what they are capturing is a true representation of "actual sound" in order to avoid false positives, shouldn't 48 kps be sufficient?

[CaveRat2]

[That is very informative and I appreciate the exhaustive reply. I understand what you are saying regarding not knowing the elements of the evp, etc. I had never really considered this, but I was under the impression that you had set those standards to eliminate the possibility of false positives. If one wanted to be confident that what they are capturing is a true representation of "actual sound" in order to avoid false positives, shouldn't 48 kps be sufficient?

Two factors would need to be considered if you use lower sample rates

First, of course is that you are aware of and have no intention beyond simply listening. With that in mind you could use 48KBPS.

Second and more important, you will need to record through a bandpass filter to block anything over 8 kHz. Reason is that should an insufficient sampling rate be used, based on the audio frequency, the possibility of aliasing increases dramatically. This can result in secondary sounds in the lower frequency regions as the sample rate hetrodynes with the higher audio frequency components. Thus these will need to be blocked to prevent them from entering the recorder'

As to the sound quality You may notice a slight difference between 48 KBPS and 96 KBPS, but not appreciably. When I conducted my tests here I used simulated EVPs containing audio components up to 15 kHz. The tests were conducted using a Fostex FR2 digital recorder. This recorder can sample up to 192 KBPS, but can also be dongraded to lower rates. One could see no appreciable difference between 192KBPS and 96 KBPS. on a scope nor could you hear any. When you drop down to 48KBPS you could observe a 3 db rolloff at 15 Khz over the 96 KBPS. Listening wise it was barely noticable. Not serious but that was were it first became apparent. Below that it was much greater and could be easily heard as well. Thus my resoning for setting these values. In a pinch 48 KBPS should work OK. Certainly better than the 8 to 14 K that most digital voice recorders use!

[CaveRat2]

I dont know if this was asked one time on here or on another website but I am going to ask this now because I am wondering about this.

Its not possible for a digital notetaker to pick up radio frequencies is it?

Also.... can you get bleed through somehow on a digital recorder if you erase and then record again over a period of time?

Yes it is possible. The digital portion likely won't respond to RF, however all digital recorders also have analog preamps in the circuit. These provide the gain for the microphone. Any unshielded or poorly shielded analog circuit can easily respond to RF signals if they become non-linear due to biasing. Thus all recorders for EVP, regardles of digital or analog must be shielded properly to provide reliable results.

No bleedthrough with digital. Should a memory location fail to erase from a previous session it usually appears as a pop or a cutout in the audio stream. But no intelligible audio unless an entire segment fails. Then it would simply be the old audio in place of the new. Not bleedthrough though, it would be clearly present. And time to replace the memory stick or get a new recorder.