Resonance

[randut]

I came across this very interesting video on google, This guy increases the frequency on his speaker under what appears to be a plate of steel. It sounds just like my PWM when I adjust the frequency although the volume is a lot lower. In the end it sounds like he blows the speaker, LOL

Anyway the pattern that it generates may give a visual representation of what takes place to the plates in solution when frequency modulation is applied to them. I didnt want to threadjack the previous post so I posted here

Its worth a look.
http://video.google.com/videoplay?docid ... =resonance

Best regards RK

[nobody]

[Pinhead]

[Danberman]

Its cool stuff

we did this in my physics class last year. There were a few things that you may want to take into account though. Im not sure how much this will affect it but a sinosuidal wave was used. If you want a good visual representation of this tie a rope to your door knob and lift it up and down. You will notice that a "wave" will go until it reaches the end of the rope, the node, and bouce back traveling in the oppisite direction. A standing wave (aka resonance) is created when the waves bouncing back are lining up perfectly with the waves traveling in the oppiste direction. When to waves meet as such they are ampified, in other words a wave with the magnitude of two, meets a wave with the magnitude to two, the resulting magnitude is 4. Similarly if they are out of phase as in one wave is coming up while the other is going down, they cancel and if they line up perfectly the net result is zero. You mentioned you were trying to find the frequencies. This won't get you too far because the resonant frequency is diffrent for diffrent objects. This is why when you strike diffrent notes on an instrument you get diffrent sounds. When a string or such is plucked all the other frequencies present in the line will quickly die out. however the resonant frequencies will create standing waves and will continue to resonante for quite a while. Furthermore, as you could see from the vid there are many diffrent resonant frequencies, this is because there are more than one frequences that create standing waves. If you have a PWM module you may try making it have a psuedo sinsuidal output by placing a good capacitor on the output, however they will charge and discharge logarithmically, not sinsuidally. Also be careful, most capacitors dont mix well with pwm signals. If you are looking to calculate resonance then i can't help you, but from my understanding it is extremly hard to do so, and rather inaccurate due do all sorts of little variables. I would suggest building a good sinsuidal signal generator, and mab hook it up to some nice mosfets to power your unit. the HUFxxxx series have some great ones that will sink 250+ watts and only cost a few bucks on digikey

[kevinsatterfield]

I think "standing wave" is use'n a(single) base wave/frequency and "resonance" is use'n" harmonics "(multiple)of the same base wave/frequency.Albeit a standing wave can be considered as resonance the "amplitude" is greatly increased when harmonics are introduced.

[aussepom]