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woolytoad
Skeptic Friend
313 Posts |
 Posted - 02/21/2005 : 04:45:48 [Permalink]
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quote:
Originally posted by Dave W.
quote:
Originally posted by Dude
If your son has a competent science teacher, you are going to help him earn a nice fat F.
Only if the kid attempts to get it to work. A competent science teacher might enjoy a display titled "The Problems Associated with Acceptance of EVP Hypotheses." Include a mock-up of Edison's machine, with a write-up on why it shouldn't work. Etc.
I'd give you an F for something like that. Sounds like you've already decided what's going to happen.
Our 4th grader needs to:
- research the problem and the theory.
- figure out the major factors that will effect experiemntal results.
- do the experiment with the proper controls.
- analyse the results, come to his own conclusion based on his results.
- see if he made mistakes and repeat if he has time.
Regardless of what happens, if his methodology is correct, then he's showed he's learned the basic scientific principles and should grade well. |
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Dave W.
Info Junkie
USA
26021 Posts |
Posted - 02/21/2005 : 11:31:58 [Permalink]
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quote:
Originally posted by woolytoad
I'd give you an F for something like that. Sounds like you've already decided what's going to happen.
Do you fault most physicists, then, for failing to pursue perpetual motion machines?quote:
Our 4th grader needs to:
- research the problem and the theory.
What is the problem and theory when it comes to EVP?quote:
- figure out the major factors that will effect experiemntal results.
My point was that those factors - with regard to EVP - appear to be overwhelming.quote:
- do the experiment with the proper controls.
What are the proper controls for an EVP experiment?quote:
- analyse the results, come to his own conclusion based on his results.
- see if he made mistakes and repeat if he has time.
How would one know one has made mistakes in a field which science doesn't touch?quote:
Regardless of what happens, if his methodology is correct, then he's showed he's learned the basic scientific principles and should grade well.
If that's the point of science fairs, then I'm annoyed that my science teachers (way back when) spent so much effort getting us to make nice presentations which taught other kids (and adults) what we learned. I mean, we got tested on our understanding of the scientific method - short essay format, even. In class. We didn't bother showing off those exams in a fair, though. |
- Dave W. (Private Msg, EMail)
Evidently, I rock!
Why not question something for a change?
Visit Dave's Psoriasis Info, too. |
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furshur
SFN Regular
USA
1536 Posts |
Posted - 02/21/2005 : 21:20:04 [Permalink]
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beskeptical, when I first read this post I looked like the little rolly eye guy, but your post said:
quote:
If they come up with different messages then have a second group listen and tell them ahead of time what to expect. In other words if one person hears "Come here" and another person hears "Go there" see if telling a listener what to expect causes them to perceive the message as expected.
What a cool experiment for a kid to run. It would teach the scientific principals of experimentation and also teach people about suggestability. Great idea - I might steal it and talk to my daughter about using it in her science fair. And if we really hear ghosts I can make a quick $1,000,000 from Randi.
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If I knew then what I know now then I would know more now than I know. |
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ktesibios
SFN Regular
USA
505 Posts |
Posted - 02/22/2005 : 02:37:31 [Permalink]
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Another experiment that could produce interesting results would be to play a set of recordings for un-prompted listeners and ask them to log any voices that they might perceive by the time (relative to the start of the recording) that they hear them.
The object would be to find out if there's a perceptible phenomenon by testing whether listeners consistently identify the questioned phenomenon in the same place- somewhat like the use of A/B/X testing to determine whether an alleged equipment artifact is genuinely audible.
There's even the possibility of making it a controlled experiment- if you use a digital audio workstation (a hard disk-based digital recording system), it might be possible to create "control" recordings- files that contain nothing but random noise created by a digital signal generator. With no microphone, analog electronics or even real-time recording involved, one could have considerable confidence that the control files contain nothing that could possibly be a legitimate EVP phenomenon. Mixing control files with "live" files in the listening session should provide an additional check on the consistency of listener responses.
Don't even think of using an analog tape recorder, most especially a cassette deck. Why? Two words- "print-through"- a well-known artifact which the writer of the EVP Web site Storm referenced doesn't seem to have ever heard of.
Audio electronics, especially recording, is the one area of knowledge in which I can claim some expertise; I've earned my living as a techie and engineer in top-flight recording studios for over 15 years- heck, I've even got a platinum record plaque hanging on my living room wall.
Anybody interesting in discussing the technical aspects of setting up a worthwhile EVP experiment is welcome to PM me.
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"The Republican agenda is to turn the United States into a third-world shithole." -P.Z.Myers |
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Dr. Mabuse
Septic Fiend
Sweden
9687 Posts |
Posted - 02/22/2005 : 03:05:50 [Permalink]
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quote:
Originally posted by ktesibios
Don't even think of using an analog tape recorder, most especially a cassette deck. Why? Two words- "print-through"- a well-known artifact which the writer of the EVP Web site Storm referenced doesn't seem to have ever heard of.
I actually made an experiment that resulted in print-through.
After having a heated discussion in school with some classmates about the workings of compact cassette (what did we know, we were only 11 years old at the time...) I went home to check. Though this was a long time ago, I still remember it because I was so surprised by the result.
The hypothesis: the tape had magnetic information, so a strong magnetic field should in theory whipe the cassette clean.
The experiment: I took a strong permanent magnet and rubbed it against the flat outside of the tape. When I played the tape again, to my surprise, the information was still there. But the tape had developed a serious case of print-through. From any particular piece of tape the recording transfered two layers in the spool. The closest layer had perhaps 10% signal strenth, and the second layer of tape had a barely audible print through, yet distict enough to be identified.
The conclusion: an audio tape can get print-throughs if subjected to a magnetic field, even if it is not dynamic.
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Storm
SFN Regular
USA
708 Posts |
Posted - 02/22/2005 : 13:43:50 [Permalink]
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So today I went up to Dade city which is about 50 miles northeast of me...Damian and I love to visit the antique shops and have lunce... it being my birthday today we decided todo just that....
I stopped into this antique shop and I am looking at the books.. This is one of my favorite hobbies..Many times in antique shops one can find very esoteric and occult type books... To day believe it or not I found a book about Thomas Edison and his talking machine circ 1931... Coincidence? Just happened to be... or a direct lead to my son's fourth grade project... I also found a most excellant book on ESP...
But the Thomas Edison book .. I mean ... tripped out... |
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Kil
Evil Skeptic
USA
13476 Posts |
Posted - 02/22/2005 : 14:04:38 [Permalink]
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| Happy Birthday, Storm... |
Uncertainty may make you uncomfortable. Certainty makes you ridiculous.
Why not question something for a change?
Genetic Literacy Project |
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ktesibios
SFN Regular
USA
505 Posts |
Posted - 02/22/2005 : 15:04:47 [Permalink]
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As a matter of fact, Doc, exposure to external magnetic fields which aren't strong enough to cause erasure does increase print-through. The external field acts as bias, helping to overcome the hysteresis of the magnetic coating. AC and DC fields will both do this; I don't know if either is more effective at promoting print-through.
Higher temperatures also increase print- there's a contact printing process for high speed duplication of VHS tapes that uses heating by a laser to promote signal transfer from the master to the target tape.
The reason that particular analog artifact would be of concern is that some people trying to record EVP have used a procedure in which the recordist asks a question, in the hope of finding a response on the tape. Any signal deliberately recorded on the tape could print to an adjacent layer in the tape pack and create what appears to be a response, way down in the tape's noise floor. Cassettes are the worst offender in this regard due to the extremely thin plastic substrates which are used to permit packing long lengths of tape into the cassette package.
Storing the tape heads out, i.e., rewound to the beginning, would also make things worse. Due to the way the vertical and horizontal components of the magnetic field of a recorded signal interact, the print to the adjacent layer inside the source layer in the tape pack is always stronger than the print to the outside layer. If the tape is stored heads out, this means that the stronger print will play back after the signal which generated it, which increases the likelihood of a false perception of a response.
That's why I stromgly recommmend avoiding analog tape in general and cassettes in particular. Digital recording, whether on tape, optical disk or hard disk is completely free of this phenomenon.
Decent hard disk recording systems have been becoming more and more affordable and common. If you know someone who plays in a band, there's a pretty good chance these days that he/she will know someone who has a digital home studio rig.
Even a minimal system- say ProTools LE with an MBox- could be used quite effectively in setting up a set of controlled, double-blinded listening tests aimed at determining whether listeners identify the presence/absence of EVP-like phenomena at a level greater than random chance would predict.
That- exploring the human perception aspects- seems to me to be the likeliest area for producing a really bang-up science project.
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"The Republican agenda is to turn the United States into a third-world shithole." -P.Z.Myers |
| Edited by - ktesibios on 02/22/2005 15:07:40 |
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Dave W.
Info Junkie
USA
26021 Posts |
Posted - 02/22/2005 : 19:19:04 [Permalink]
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Hijack for ktesibios:
In every regular version of Squeeze's "Tempted," I hear the first few words - "I bought a toothbrush" - clearly though quietly, shortly before they're actually sung at the level maintained by the rest of the vocals.
Because I've heard it in the music video, on the CD, and on a cassette a roommate used to have, could this be an example of a print-through on a master tape? Or was it intentional? |
- Dave W. (Private Msg, EMail)
Evidently, I rock!
Why not question something for a change?
Visit Dave's Psoriasis Info, too. |
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H. Humbert
SFN Die Hard
USA
4574 Posts |
Posted - 02/22/2005 : 19:32:14 [Permalink]
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quote:
Originally posted by Dave W.
Because I've heard it in the music video, on the CD, and on a cassette a roommate used to have, could this be an example of a print-through on a master tape? Or was it intentional?
Oh! There is a Led Zeppelin song that does it too. Heartbreaker. You hear a faint echo before the words are actually sung. (The part where he sings "Way down inside...woman...you need it.") I had always assumed it was intentional too, but reading your post has got me wondering now.
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"A man is his own easiest dupe, for what he wishes to be true he generally believes to be true." --Demosthenes
"The first principle is that you must not fool yourself - and you are the easiest person to fool." --Richard P. Feynman
"Face facts with dignity." --found inside a fortune cookie |
| Edited by - H. Humbert on 02/22/2005 19:33:15 |
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Dave W.
Info Junkie
USA
26021 Posts |
Posted - 02/22/2005 : 20:38:29 [Permalink]
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I think it is intentional on the Zepplin tune, as it sounds slightly different. It's not just a quieter version of the loud lyrics, it's a quieter and fuzzier and... different... version of the lyrics which follow. It's hard to really describe the subleties I remember hearing.
Plus, there's nowhere near enough time between the two for the tape - big studio reels, I'm guessing - to have wrapped around on itself. In the Squeeze song, there's a lot more time. |
- Dave W. (Private Msg, EMail)
Evidently, I rock!
Why not question something for a change?
Visit Dave's Psoriasis Info, too. |
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Kil
Evil Skeptic
USA
13476 Posts |
Posted - 02/22/2005 : 21:07:46 [Permalink]
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| The effect in the Zepplin tune was called reverse echo. At least, that's what it was called when I was recording... |
Uncertainty may make you uncomfortable. Certainty makes you ridiculous.
Why not question something for a change?
Genetic Literacy Project |
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ktesibios
SFN Regular
USA
505 Posts |
Posted - 02/22/2005 : 22:09:30 [Permalink]
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The most commonly used reel size in studio work has flanges 10.5" in diameter. There are 12" and 14" reels, but they're pretty rarely used; one common use for 14" reels, though, was album assembly- where you take the mix masters chosen for the record and splice them together in the correct order, with leaders for inter-song timing, onto a single reel which will go to the mastering studio. Album assemblies with 30 IPS masters commonly resulted in two 14" reels- one for each side of the phonograph record. The diameter of the NAB hub at the center of the reel is about 4.5", so at 30 IPS the delay between the source signal and a pre or post echo due to print-through would vary from just about 1 second (for a 10.5" reel full to capacity; for a 14" reel just under 1.5 second) down to just under 1/2 second, depending on where you were in the reel. At 15 IPS these times would be doubled.
There's another phenomenon in analog recording that can produce a pre-echo, and this one is peculiar to phonograph records. It's called "groove echo", and it results from the cutting stylus slightly displacing the lacquer material on the master disc. This can produce a small deformation in the wall of an adjacent groove which has already been cut, thus transferring some signal to that groove as a pre-echo. The problem can be magnified in the plating process used to produce the matrix from the lacquer master. For a 33 1/3 RPM album, the groove echo should be displaced from the source signal by 1.8 second. This is something which happens only in the disc-cutting process, so if the same pre-echo is present on tape or CD, this possibility is ruled out.
In a good analog album assembly, the head leader for each song is cut very tightly- the splice will be a tiny fraction of a second before the downbeat. Leader tape has no magnetic coating and is incapable of taking a print, so print-through on the master tape is an unlikely explanation of a pre-echo at the top of a song, unless blank tape was used for spacing instead of leader tape.
If it's on a vinyl record, it could be groove echo. If it's on a cassette, it could be print-through in the cassette itself. If it's the same in multiple media, the odds are that it's intended to be there. Since CD assembly nowadays is nearly all done with DAWs and the extremely accurate editing capabilities of these systems makes it possible to cut out any extraneous zark to within a few tens of microseconds of the start of the song, if it's on a newish CD, you can bet that someone wanted it to be there.
BTW, I got it backwards in my description of print-through- the print to the outer layer is normally stronger than the print to the inner layer. Heads-out storage tends to produce a stronger pre-echo than tails-out storage. One of the reasons that tails-out storage is standard studio practice is that pre-echo, particularly when it intrudes into a lead-in or quiet section, is more obnoxious than post-echo. (The other is that print will tend to decay a little when the tape is fast wound, and tails-out storage forces you to rewind the tape before playing it.)
This industry is now so committed to digital recording that on the rare occasions when I'm called on to do a 24-track machine alignment, which five years ago I had to do nearly every day and could do in my sleep, I actually have to stop and think about the next step. Digging up information about analog recording media now means rooting about in my brain's backup memory and consulting reference books- hence the odd mistake when I wing it. 
edited to add: I also oughta mention that for professional reel-to-reel tape print-through under most circumstances is pretty well buried in the tape's noise floor. I can only recall one session where it actually gave me a problem, and in that one we were taking an electric guitar track recorded directly from the guitar's output and routing it to an amp in the studio so as to cut a perfectly synchronized "double". The amp, which was a hot-rodded vintage Marshall with all the knobs cranked up to 11, actually had enough gain to amplify the print, which wasn't really perceptible when listening to the original track, into a bothersome echo.
Listening to a recording with insane amounts of amplification- isn't that pretty much what some EVP enthusiasts do? 
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"The Republican agenda is to turn the United States into a third-world shithole." -P.Z.Myers |
| Edited by - ktesibios on 02/22/2005 22:26:26 |
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H. Humbert
SFN Die Hard
USA
4574 Posts |
Posted - 02/23/2005 : 01:17:15 [Permalink]
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Ah, I misspoke. It's Whole Lotta Love that has the reverse echo.
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"A man is his own easiest dupe, for what he wishes to be true he generally believes to be true." --Demosthenes
"The first principle is that you must not fool yourself - and you are the easiest person to fool." --Richard P. Feynman
"Face facts with dignity." --found inside a fortune cookie |
| Edited by - H. Humbert on 02/23/2005 01:17:28 |
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Dave W.
Info Junkie
USA
26021 Posts |
Posted - 02/23/2005 : 05:32:11 [Permalink]
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quote:
Originally posted by ktesibios
In a good analog album assembly, the head leader for each song is cut very tightly- the splice will be a tiny fraction of a second before the downbeat. Leader tape has no magnetic coating and is incapable of taking a print, so print-through on the master tape is an unlikely explanation of a pre-echo at the top of a song, unless blank tape was used for spacing instead of leader tape.
Thanks for all the explanations, but one thing I'd like to point out is that "Tempted" has a good instrumental intro before the lyrics start. It's towards the end of that intro that the "pre-echo" of the first words are heard. Dammit. Now I'm going to have to find the cut and measure how long the delay is... |
- Dave W. (Private Msg, EMail)
Evidently, I rock!
Why not question something for a change?
Visit Dave's Psoriasis Info, too. |
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