Unable to account for frequency related to Magnet being pulsed by Inductor

[duff]

Perhaps someone can explain the following:

I sat a cylinder neo magnet on top of an air core inductor wound with #10 magwire and noticed it was singing at 959Hz. What is remarkable is that there are actually two tones (possibly 3), the second of which is approximately an octive higher (959Hz & ~1918Hz) and if I tune to either side of the 959Hz the lower tone starts wobbling so there must be two low frequency tones.

The tones are easiest to hear when the magnet is  placed on the top of the plastic spool coil form and directly over the winding although I can also hear the tone while holding it in my hand, so the tone is not a result of the vibration of the plastic spool nor is it coming from the winding. I tried various other neos of different size and stength, some of which were rectanglar in shape and the tone did not change. I also tried a ceramic block magnets - tone did not change though it was not as loud.

All this was observed while pulsing the inductor (pw=100us)  with the circuit drawing 20ma. If I increase the current by increasing the pulse width the tone gets louder.

Cylinder Neo: dia=1", height=1"

Spool Circumference = 10.984 inches
Spool Diameter = C / π = 3.4963 inches
Spool Height = 7.48 inches
Wire Diameter = 0.1056 inches
Turns/layer = 67

Inductor
Measured Inductance: 3.98 mH
Measured Resistance: 0.395 Ω

Ohms/Kft: 0.998900
Calculated wire length: 395 feet

Resonant Freq: ~100KHz

-Duff

[TinselKoala]

Do you live in the US or the UK?

960 = 60 x 16  so if you are in the US you are probably picking up the mains freq.

You can Hear the tone?
You can hear it audibly without electronic amplification?
How are you measuring the frequency?
What is the frequency of your driving signal?

[Mk1]

If you did achieve get the right freq of the magnet , it will start singing it may also amplify the sound of the coil , since if the magnet moves ,this is basically a speaker. So 2 freq the magnet and the generator , like tuning a piano or a guitar , when to freq are close together you will start hearing a third freq this one can only be heard when you have two freq slightly out of tune , the third freq will start to slow down and go out if you get to close , but can also go up to one octave up so double the freq, so that third freq is really special since its like a ghost note adjustable in a really close range of freq .
I believe you did the same with a magnet, make it sing make it sing !

Mark

[innovation_station]

If you did achieve get the right freq of the magnet , it will start singing it may also amplify the sound of the coil , since if the magnet moves ,this is basically a speaker. So 2 freq the magnet and the generator , like tuning a piano or a guitar , when to freq are close together you will start hearing a third freq this one can only be heard when you have two freq slightly out of tune , the third freq will start to slow down and go out if you get to close , but can also go up to one octave up so double the freq, so that third freq is really special since its like a ghost note adjustable in a really close range of freq .
I believe you did the same with a magnet, make it sing make it sing !

Mark

WOW BRO!!



LOVE THE MUSIC!!

IST!

[duff]

Do you live in the US or the UK?

960 = 60 x 16  so if you are in the US you are probably picking up the mains freq.

You can Hear the tone?
You can hear it audibly without electronic amplification?
How are you measuring the frequency?
What is the frequency of your driving signal?

Yes, the tone is audiable without amplification.

The frequency corresponds to the function generator readout plus I attached a small speaker to the FG output to verify it was the same frequency that the magnet was singing.

If I put a piece of paper under the magnet, I can raise it to about 6" above the inductor and still hear the tone.

If you did achieve get the right freq of the magnet , it will start singing it may also amplify the sound of the coil , since if the magnet moves ,this is basically a speaker. So 2 freq the magnet and the generator , like tuning a piano or a guitar , when to freq are close together you will start hearing a third freq this one can only be heard when you have two freq slightly out of tune , the third freq will start to slow down and go out if you get to close , but can also go up to one octave up so double the freq, so that third freq is really special since its like a ghost note adjustable in a really close range of freq .
I believe you did the same with a magnet, make it sing make it sing !

Mark

Mark, I believe you are partially correct.

The paper or plastic spool acts as a diaphragm amplifying the vibration of the magnet. If I take the frequency up the singing follows.

However, there seems to be an inherent frequency, 959Hz, that  spans the multiple magnetics I tried and the wobble or beat note seems to reside in all the magnetics.

-Duff