EEVblog 1743 - Mechanical Vibration Detection with your Oscilloscope Probe

[thm_w]

How low in frequency would an MLCC  be able to pick up mechanical vibrations?

Good question, a piezo disk speaker is more like 2kHz+ resonant frequency.
This is showing 600Hz and down to 100Hz: https://sci-hub.box/10.1109/TEMC.2020.2993850
This article mentions 20Hz, though just in reference to the above: https://pmc.ncbi.nlm.nih.gov/articles/PMC9147252/

I’m still looking for a device than can pick up the noise generated by a water leak in a pipe for domestic use.

Can't a thermal camera can do this? The water is usually much colder or warmer than the environment around it.

[amyk]

A product I worked on long ago used the decoupling caps on the board to generate diagnostic beep codes without adding a separate speaker. By choosing an appropriate frequency at which to wake up the MCU, it will draw pulses of current and make the caps sing enough to be audible.

[golden_labels]

Amyk: are you serious? I have to ask, given the nature of the video and this thread (April 1st).

[Sorama]

How low in frequency would an MLCC  be able to pick up mechanical vibrations?

Good question, a piezo disk speaker is more like 2kHz+ resonant frequency.
This is showing 600Hz and down to 100Hz: https://sci-hub.box/10.1109/TEMC.2020.2993850
This article mentions 20Hz, though just in reference to the above: https://pmc.ncbi.nlm.nih.gov/articles/PMC9147252/

I’m still looking for a device than can pick up the noise generated by a water leak in a pipe for domestic use.

Can't a thermal camera can do this? The water is usually much colder or warmer than the environment around it.

No, it can not.

[EEVblog]

The scope probe is picking up 11 kHz, while the acoustic camera showed 22 kHz. So chances are the scope probe still pics up an electromagnetic field, not acoustic.

Nope 

[EEVblog]

Why is the camera FFT showing Dave's voice up to 40..50KHz ?

That is a good question. There can actually be some contend to higher frequencies in the voice, but it could also be harmonics in the signal chain. It still looks like a pretty strong effect.

Yes, good questions, I don't know. I haven't really tested it properly yet apart from this quick video.
Mike's Electric Stuff also has one and said he might release a video soon.

[SiliconWizard]

Ceramic capacitors making audible acoustic noise is definitely not a rare thing in switching power supplies. Can be veryy annoying.

The trick to limit that is to add some mechanical decoupling from the PCB itself, which is what resonates and makes it audible, for instance by adding slots on each side of the capacitor. Of course downside is that slots will break power/ground planes so that's another potential issue. Pesky MLCCs. Otherwise some damping with silicone paste or something like that. If thermals allow.