Very quick post to share a successful gutting of an old computer loudspeaker (external) so that phyphox Tone generator makes both the speaker and a neodym magnet (hanging from a spring over an empty coil of copper wire) vibrate with a very slow beat from a combined 10.95 and 11 Hz signal.
Next step (hopefully) is to send that signal through a diode bridge and then replace the electric motor in the experiment about driven oscillation and resonance.
If it was possible to program the beat to "sweap" from 0.1 Hz to maybe 20 Hz you could perhaps explore resonance in simple small springs in one experiment/measurement using Acceleration Spectrum.
Have not yet tried if neodym could move heavier strings (double bass, 20-100 Hz).
the indicated sweep is for acoustic frequencies. Erik's idea is to realize a sweep of subhertz frequencies using acoustic beats passed trough a diode bridge. So the obtained signal can be used to drive slow resonances (a mass on a spring).
I thought that with the dual tone generator it is a fixed frequency and a sweep – brief frequency range, of course. It required certainly more though. Thanks for your important remark…
(02-14-2022, 12:38 PM)Jens Noritzsch Wrote: I thought that with the dual tone generator it is a fixed frequency and a sweep – brief frequency range, of course. It required certainly more though. Thanks for your important remark…
I don't have equipment to measure how slow you can make the beat but I can easily hear 0.1 Hz beats at both high and low component frequencies.
I can also see the loudspeaker membrane (and neodym magnet as in picture) vibrate at very low frequencies like 5 Hz, and see the beat from component 5.9 Hz + 6 Hz signals.
So I guess there are two sweeps to program, one where the beat frequency is fixed (e.g. 0.5 Hz to surely be below the base frequency of a given mass+spring) and the other where beat frequency goes from let's say 0.5 to 100 Hz. The former (fixed) to find the frequency where you get the strongest magnetic field to pull the mass+spring and the latter to get the what you want: the full resonance spectrum of a given mass+spring.
Didn't have time to send the beat signal through the diode bridge yet.
02-17-2022, 05:32 AM (This post was last modified: 02-17-2022, 05:34 AM by Erik Josefsson.)
It worked! See attached video. Just needs some fine tuning :-)
Iron rod is about 30 cm with three neodym magnets (12x3 mm) attached hanging in a fairly soft spring about 30x7 mm. It is not difficult to attach a phyphox phone to it, so hopefully you could do a "beat sweep" and look at the Acceleration Spectrum on the phone.
Copper wire is about 135 metres long with Ø 0.55 mm. I don't know number of loops. Came out of the box with both wire ends connectable.
I hope to find a frequency that is bearable to listen to so that you can both hear the beat from the speaker and see it from the light bulb and then follow how it drives the oscillation of the mass+spring.
