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Suppose that we have a $2$ by $2$ by 2 $cm^3$ closed box, made up of glass, with thickness $0.1 cm$. Yes, it is a very small box. Let's say in that box there is a ball (also made with glass) with diameter $0.5 cm$. If we shake the box as fast as we can for one minute, making the ball bouncing like crazy inside the box, how do we measure (exactly or approximately) how many times the ball bounces/makes contact with one out of the six sides of the cube?

I never heard of any device that can do this. The closest ones are vibration meter and drumometer, I believe? However, it looks like vibrameter does not measure the number of bounces and drumometer is, well, too huge? Perhaps we need a mini drumometer? I mean, whatever that device is, does that mean a very small sensor that is connected to the device must be put into that side of the cube?

Also, since the stuffs are made with glass, meaning they produce sound, can we measure the bounce by measuring (from the outside) the sound made from the shaking? My guess is that a device called sound level meter is what we need but it still won't count the bounce?

Note: Please correct my tags/title if needed as I have very little engineering background.

Additional question: What if (instead of one particular face) we measure the number of impacts coming from any face of the cube? Well, in this case, we don't need cube, but it can be a ball-shaped glass large enough to contain the small one.

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I would attach some kind of microphone or piezo pickup to the center of the side of the box that you're measuring.
Now, the devil is in the calibration - you'll need to do something like tapping the "test" side and seeing what the piezo output amplitudes are, then tap the other 5 faces of the cube and compare. If there's a reasonably large difference in amplitude, or even in shape (spike vs. wider pulse or different decay tail), then you may be able to analyse the results of shaking the box via pulse height discrimination and/or FFT signatures.

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    $\begingroup$ Or an accelerometer $\endgroup$
    – joojaa
    Aug 29, 2018 at 19:53
  • $\begingroup$ @joojaa maybe, but since glass is a stiff material, an accelerometer will mostly measure the shaking motion, not the impacts. $\endgroup$
    – alephzero
    Aug 29, 2018 at 20:19
  • $\begingroup$ @alephzero I tested it seems to work fine after filtering the signal a bit i can clearly see the hit. But my glass is bigger and my accelerometer expensive. I did have problems with a piezo id have to build a pre amp to be more definitive. $\endgroup$
    – joojaa
    Aug 29, 2018 at 20:25
  • $\begingroup$ I have added another case in my edit after considering @Carl's answer. Would the measurement be done more easily? Or, the amplitudes would appear to be "continuous" since there'd be no noticeable difference? $\endgroup$
    – bms
    Aug 30, 2018 at 9:05
  • $\begingroup$ @alephzero well, depends on the bandwidth of the accelerometer. $\endgroup$
    – Carl Witthoft
    Aug 30, 2018 at 17:51

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