Unbelievable Discovery - "singing metal"!

[Funfinder]

This is no joke but very interresting:
If you hold an old horseshoe with endings down near the coils of your detector with good ears perhaps you will hear a very high but silent singing sound the metal itself produces! The Fisher 1266-X creates this effect with good signal, the Garrett Ace 250 only just a bit and Jeohunter nothing, so there are differences.

What kinda crazy resonance here's working?

Has the audio signal the same frequency the search-coils are using?

Perhaps this also works with other kind of "musical" metal objects having a shape that supports vibration.

Please tell me an explanation of that effect and if you can reproduce it.

[J_Player]

This is no joke but very interresting:
If you hold an old horseshoe with endings down near the coils of your detector with good ears perhaps you will hear a very high but silent singing sound the metal itself produces! The Fisher 1266-X creates this effect with good signal, the Garrett Ace 250 only just a bit and Jeohunter nothing, so there are differences.

What kinda crazy resonance here's working?

Has the audio signal the same frequency the search-coils are using?

Perhaps this also works with other kind of "musical" metal objects having a shape that supports vibration.

Please tell me an explanation of that effect and if you can reproduce it.

I never heard of this, but the first thing that comes to mind is eddy currents in the metal causing the two ends of the horse shoe to vibrate like a tuning fork. In theory, this could happen if eddy currents caused a magnetic field in the horse shoe that was strong enough to cause some small force of attraction and repulsion between the two sides. But to gain any mechanical advantage, the eddy current fields would need to alternate at a frequency that is resonant with the natural frequency that the horseshoe vibrates at (or a harmonic of that audio frequency) to make a sound.

You can sometimes hear sounds from coils wound on iron cores caused by alternating magnetic fields when the coils or core laminations are slightly loose and vibrate at the frequency of the AC in the coils. It sounds like this may be a similar phenomenon which is weaker because of the distance from the search coil to the horse shoe. If this is what is causing the sound, then I would think the amount of current in the search coil as well as the coil frequency will determine the strength of the sound you hear from the horse shoe.

You could test this theory by replacing the horse shoe with other metal samples that are shaped more like a tuning fork, and with a lower mass attached to a sound box (cigar box or similar) to boost the sound even more. Maybe a U-shaped coat hanger wire would make louder sounds if attached to a sound box. You can easily trim the ends of a coat hanger "U" to adjust its mechanical vibration frequency so it is in tune with the search coil. Don't forget to check to make sure the sound is coming from the target metal, and not from inside the search coil. Loose coil wires can also make sounds.

Best wishes,
J_P

[Funfinder]

Thanx J_Player - this must be it:

if eddy currents caused a magnetic field in the horse shoe that was strong enough to cause some small force of attraction and repulsion between the two sides. But to gain any mechanical advantage, the eddy current fields would need to alternate at a frequency that is resonant with the natural frequency that the horseshoe vibrates at

But this phenomenon must be some vibration or resonance-effect at molecular level:

The "magic tune" comes directly from the both site-centers of the horseshoe, a bit nearer located to the ends. Best gain if there is ca. a 2.5cm /1 inch distance between coils and horseshoe-endings.

I could record it with a simple Webcam-Mic but you need a good headphone because of the very high frequency. Processed it through a highpass-filter for eliminating disturbing noises.

As I tried recording it with a walkman with inbuilt Mic I had almost the same high-frequency in my earphones - but without any horseshoe! With a coat-hanger so far no success.

It reminds me a little bit on the bright sound of silver but is slightly different.

[J_Player]

Thanx J_Player - this must be it:



But this phenomenon must be some vibration or resonance-effect at molecular level:

The "magic tune" comes directly from the both site-centers of the horseshoe, a bit nearer located to the ends. Best gain if there is ca. a 2.5cm /1 inch distance between coils and horseshoe-endings.

I could record it with a simple Webcam-Mic but you need a good headphone because of the very high frequency. Processed it through a highpass-filter for eliminating disturbing noises.

As I tried recording it with a walkman with inbuilt Mic I had almost the same high-frequency in my earphones - but without any horseshoe! With a coat-hanger so far no success.

It reminds me a little bit on the bright sound of silver but is slightly different.

It sounds like the horse shoe is acting like a tuning fork. I doubt it is vibrating at the fundamental frequency of the horse shoe, but probably a higher harmonic. I suppose the eddy currents are causing the shoe to jiggle along it's length. You may be able to hear several audio frequencies including the high pitch one on your recording if you hold the horse shoe from a string and ping different points on the side of it with a spoon.

You could try passing the detector over a fork or a u-bend piece of stiff wire held near a sound box to see if you hear any sounds to help confirm it is caused by the coil. Maybe it works better for iron than non-ferrous metals. One way to hear some sounds from other metals could be to hang the metal from a string that is tied to the microphone housing. Any vibrations in the metal will travel up the string and conduct to the microphone as long as there is not much insulating foam in the way. Of course it would be good to tie off the metal in the direction it is expected to vibrate the most. ie: a straight piece of stiff wire suspended horizontally and tied off near the middle of the length, but slightly to the side of the center.

Best wishes,
J_P

[Funfinder]

> but probably a higher harmonic

This could be, but I wonder why the audio signal emmits from two central points.

The Fisher 1266-X uses 4,8 kHz but the heard sound seems around 12-15 kHz.

I tested and recorded the normal "pling" of the old forged iron horseshoe (perhaps around 150-200 years old) and it sounds nearly the same throughout the whole bow.
(the recording is from one end to the other and I added the orig. horseshoe.jpg above)

Admin Qiaozhi here has an 1266-XB and could also make some verification tests.

topic Sound box:
How would you like those experiments and what kind of sound box should I use? A simple resonance room, a little speaker or a metal box?
I tried a usual stainless steel fork but heard nothing so far. But I digged out alot old forged metal objects a few weeks ago so I will continue my test with those.

I think the detectors frequency gets transformed into audible signals by the special consistence of that old forged metal - maybe comparable somehow with "radio signals" on amalgan-fill-ins.

It was interresting to pinpoint exactly the both centers of the audio-source with the plastic microfone. It come directly out of the metal. Seems the resonance adds up and cumulates in those centers.


Next time we create detectors which force the buried metal-objects to make loud noises themselves!

[J_Player]

topic Sound box:
How would you like those experiments and what kind of sound box should I use? A simple resonance room, a little speaker or a metal box?
I tried a usual stainless steel fork but heard nothing so far. But I digged out alot old forged metal objects a few weeks ago so I will continue my test with those.

You can get a cigar box or similar cardboard box and cut a large hole in one of the large faces similar to the hole in a guitar. Then tape the metal object to the top of the box with the forks of the "u" hanging over the open hole. It will probably work better if one side of the U is taped down with the other side up in the air perpendicular to the face of the box. Then hold the metal detector near the fork to see if you can get it to make a sound. Try adjusting how far the metal hangs over the hole to find the best sound level. The idea is to use fairly thin, but stiff cardboard or wood that will vibrate and boost the sound like a guitar does. In order to work, you want a place along the length of the fork to be taped down tight to the edge of the hole, so it causes the face of the box to vibrate at that edge. Then the small vibration at the face of the box will echo inside and should be easier to hear around the hole.

This also might work by simply suspending the metal inside a 5 gallon bucket to enclose the sound where it will echo instead of dispersing the sound. Another idea is to cut several strips of aluminum foil and hang them alongide like an air capacitor and see if they make some audible sounds due to eddy currents causing them to make repulsive forces between each other. Maybe spacing of 1/8 inch or so would work.

...Next time we create detectors which force the buried metal-objects to make loud noises themselves!

Sure, If you can make a detector that makes only gold vibrate with 80db+ sounds from under the ground, you could become rich in the metal detector business.
If you can do it at long range, then you could become rich in the treasure hunting business.

Best wishes,
J_P

[Qiaozhi]

Admin Qiaozhi here has an 1266-XB and could also make some verification tests.

I tried the same experiment with two different horse shoes, and couldn't hear any ringing.

[WM6]

I tried the same experiment with two different horse shoes, and couldn't hear any ringing.

Of course, you are normal, without auditory hallucinations.

[Fred]

Of course, you are normal, without auditory hallucinations.

Come on, this effect doesn´t seem so extraordinary, just the right weight and dimensions so it can produce some audible oscillation...

[WM6]

Come on, this effect doesn´t seem so extraordinary, just the right weight and dimensions so it can produce some audible oscillation...

Agree Fred. We need only shoe from musical horse.

[SVEN1]

I hear ringing in my ears all the time.......must be gold all around me or horsehoes or maybe all that bent wires in the wall, scissor handles, tweezers, pipes..............no escaping it.

[Fred]

I tried the same experiment with two different horse shoes, and couldn't hear any ringing.

For this to work you must remove the horse from the horseshoe Qiaozhi...

[Qiaozhi]

For this to work you must remove the horse from the horseshoe Qiaozhi...

Really?? No-one mentioned that!

[kt315]

Funfinder, seems you still did not finder a girl who will sing you sweet song. not a metal sings... her aromatic ripe lips will be singing you THE song.
good luck you on this way

[Funfinder]

Sorry 4 l8 reply, I've been treasure-hunting and found a very old golden ring.

Well my friends, seems some perhaps unscientific orientated guys around here don't take this phenomenon for serious...

OK, last try - look at this video:
http://www.multiupload.com/WHQFJF6AWN

At the end I had to skip the cam for sound recording, because the mic is on the top side. The noise is silent and almost ultrasonic, so with cheap PC-Speakers or "Heavy-Metal-Ears" you will hear: nothing!

WM6: You're an illusion, because you can't accept reality or better: Reality rejects you!

kt315: Wow - sexy arabic Jeanny - did you rub your "wonderlamp"? btw. Carole Samaha sings nice arabic song: "Ghaly Alayi".

Qiaozhi: What kind of coil did you use? Mine is 12'' and the eliptic coil is the same size as the horseshoe endings as you can see in the clip.

J_Player:
Thank you for the "resonance room"-instructions , but paper or wood won't work, 'cause this is at the border to ultrasound. A metal pipe or metal funnel may capture the weak signal, but I doubt there is any amplification with usual equipment. It's almost comparable with a dog-whistle.


Too bad, so far I didn't found any metal-objects everybody has. However, old forged iron objects should work if you can "pling" a melodic sound out of them by finger, hammer or whatever.

But, as I told you, this also works with other detectors - like the Garrett Ace 150 or 250, but not that "intensive".
The stronger the radiation, the better the eddy-currents.

A coil, emitting at 4,5kHz with 220V. and 500W. would make not only old iron singing real loud...