interesting phenomenon

Yep, first noticed that phenomenon when removing tape the help film to spool in a darkroom. Removing the tape generated light.

I bet it's similar, or exactly, the same thing you get when you break wint-o-green lifesavers. I think that sensitive light detectors are being put underground to measure the light given off from clays in the earth that are disturbed by movement, such as fault slippage. ERS

Static electricity being generated.

Common problem handling X-Ray and other film before development.

Didn't know that you could hear it in the AM band though.

Hugh

Must be why that crackling noises I used to hear while listening to "Sgt. Preston of the Yukon" and "I love a mystery" when all we had was AM radio --- was called "static".

Jeff

Ever wonder why it was called friction tape. Take a roll into the dark and unroll some. Fascinating. kk

Very cool story! Methinks it's static, with high enough voltage and current to create a magnetic field that your radio could pick up. I wonder that if you tried it with any other radio whether it would still work. I think not, given the exact circumstances required to make it happen. There's some fancy terms for it, but they elude me at the moment.

Now I'm wondering if it was the wire to the headphones that was picking up the sound. Then it wouldn't matter what frequency the radio was tuned to. ERS

Foam tends to create static electricity - the sparks get picked up by an am radio (in general an FM radio will not pick it up for several reasons). Take a piece of foam in the dark, let your eyes adjust then rip it and watch the sparks. I used to see the same thing with the tape on the end of 35mm film when I pulled it off in the darkroom before loading the film in the tank for processing. Some foams are really bad for static.

mikey

So since I was listening to FM what gives? Was it the earphones? ERS

Ooops - mis-read on my part - thought you said AM. FM is less sensitive to the phenomena for a couple of reasons 1) much higher frequency and

2) "theoretically" FM only is sensitive to the Frequency Modulation of the signal. On weak signals (or cheap receivers), they do tend to pick up the static etc. The sharp pulse of the discharge has a very fast rise and fall time -- this means it has lots of high frequency components in the signal it sends. You were probably hearing the edge of the pulses. Look at the old spark gap transmitters (first radio transmitters). Can you say "splatter" - they ran an arc !! with a "tuned circuit" on the output that fed an antenna. Many years ago (early days of personal computers), back in the CP/M era, one of the favorite programs around allowed you to play tunes on your radio simply by holding it close to the computer - they wrote code to strobe the various address/data lines at the rate they wanted and you picked up the RFI from the computer.

mikey

Mylar "packing tape" is an electret.

It has a built in charge. Sufficient to actually work as a self energized diaphragm for a condensor (electrostatic) loudspeaker - although not a particularly good one.

dunno if it was a mylar tape.

_-_-bear

Eric R Snow wrote in news: snipped-for-privacy@4ax.com:

Did it sound anything like the file at this link?

If it did, the aluminum was actually broadcasting ;) (The adhesive would have been acting as the electrolyte, your chisel as the dissimilar metal)

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There is a form of electricity called triboelectricity. It is related to friction, but can indeed be induced when seperating adhesive surfaces. Usually it is more intense with tape on a non-conductor. Try removing a good tape from a surface in a completely dark room. You may well see sparks and a plasma-like glow.

Have you ever seen somebody chew wintergreen lifesavers in the dark? (experiment best performed with a member of the opposite sex btw)

Jim

Yep - did a paper on the subject. Try good 'ole standard 3-M magic tape. zaps nicely.

Martin