What Causes the Strange Sound When Magnets Are Used with Headphones and a Disc?

[Samson4]

I did a little experiment the other day. It involved connecting headphones to a copper disc and a battery. Then I placed a magnet under the disc. When current flows with the magnet present I get this strange sound similar to squeezing ice. What am I hearing? I don't believe it to be the electrical contacts.

Think of a homopolar motor with the disc held stationary and headphones connected in series.

 

[anorlunda]

That's a fun question. Moving the magnet will cause eddy currents in the disc which might be detected by the pickup. Other than that, I have no idea.

 

[Samson4]

That's a fun question. Moving the magnet will cause eddy currents in the disc which might be detected by the pickup. Other than that, I have no idea.

Do you think its possible that its the sound of electrons squeezing past impurities of the conductor? Or maybe the sound of electrons interacting with a magnetic field.

 

[anorlunda]

No. Headphones don't react to sounds, they respond to electric signals in the wires. Headphones convert those electric signals to sound.

A microphone converts sound to electric signals, but you don't have one.

 

[olivermsun]

No. Headphones don't react to sounds, they respond to electric signals in the wires. Headphones convert those electric signals to sound.

A microphone converts sound to electric signals, but you don't have one.

I'd have to imagine that the transduction would work both ways, in both devices, to at least some extent.

 

[berkeman]

I did a little experiment the other day. It involved connecting headphones to a copper disc and a battery. Then I placed a magnet under the disc. When current flows with the magnet present I get this strange sound similar to squeezing ice. What am I hearing? I don't believe it to be the electrical contacts.

Think of a homopolar motor with the disc held stationary and headphones connected in series.

Can you post a picture or sketch of how you are setting this up? Thanks.

 

[arydberg]

There is a similar experiment done by connecting a transformer winding to the input of a hi fi amplifier and bringing a magnet close to the core of the transformer. You can hear clicks as the magnetic boundaries pass over each other.

 

[Samson4]

Can you post a picture or sketch of how you are setting this up? Thanks.

Ill post a picture after work.

There is a similar experiment done by connecting a transformer winding to the input of a hi fi amplifier and bringing a magnet close to the core of the transformer. You can hear clicks as the magnetic boundaries pass over each other.

Yes, but the magnet is stationary. It is sitting under the copper disk.

No. Headphones don't react to sounds, they respond to electric signals in the wires. Headphones convert those electric signals to sound.

A microphone converts sound to electric signals, but you don't have one.

Im suggesting the electrons are carrying some type of noise into the signal.

 

[anorlunda]

Im suggesting the electrons are carrying some type of noise into the signal.

That's wrong thinking. If the electrons made sound, you could hear it with a doctor's stethoscope, not electronic headphones.

Don't forget that a magnet rubbing a disc is metal rubbing on metal, that makes a scrape noise even if there is no magnet.

 

[Samson4]

That's wrong thinking. If the electrons made sound, you could hear it with a doctor's stethoscope, not electronic headphones.

Don't forget that a magnet rubbing a disc is metal rubbing on metal, that makes a scrape noise even if there is no magnet.

I don't think I am explaining it well. When I say noise I don't mean something that can be heard. I mean interference or static that is converted into sound by the headphones. Again, I am not sure why this is happening. But, I do want to articulate my theory so that if I am wrong, I can understand why.

 

[anorlunda]

I don't think I am explaining it well. When I say noise I don't mean something that can be heard. I mean interference or static that is converted into sound by the headphones. Again, I am not sure why this is happening. But, I do want to articulate my theory so that if I am wrong, I can understand why.

That's better. Then I return to my answer from post #2.

Moving the magnet will cause eddy currents in the disc which might be detected by the pickup.

What you called "interference or static", I called "eddy currents". For an explanation, read this article. https://en.wikipedia.org/wiki/Eddy_current

 

[tech99]

I did a little experiment the other day. It involved connecting headphones to a copper disc and a battery. Then I placed a magnet under the disc. When current flows with the magnet present I get this strange sound similar to squeezing ice. What am I hearing? I don't believe it to be the electrical contacts.

Think of a homopolar motor with the disc held stationary and headphones connected in series.

This sound like breathing or clicking is when the domains of the magnet are being aligned by the applied field. It is only heard when the field is changing.

 

[davenn]

I don't think I am explaining it well. When I say noise I don't mean something that can be heard. I mean interference or static that is converted into sound by the headphones. Again, I am not sure why this is happening. But, I do want to articulate my theory so that if I am wrong, I can understand why.

again so we could all understand what you are doing ... a photo or two would help lots, else we are all just guessing

 

[Samson4]

This is how I set it up. This time, I didnt get the effect without holding the wire. So I will charge the batteries and try again tomorrow.

The very first time I did it I used more than 1 disc. They were disc cut out of aluminium foil and stacked where the current flows out of the center of 1 disc and into the center of another. The set up in the picture is what I used a few days ago.