Depends where you stick them on. I am using them in my diy raingauges and one of my first prototypes had a too thin surface (where the raindrops fall on) causing a light rainshower on my graph when someone was talking within a metre or 2.
It doesnt add anything. It replaces all mechanical stuff and makes the gauge maintenance free. An ESP8266 translates the sound of the raindrops to an amount. My first prototype is still running fine after 5 years outside.
Piezoelectric pickups are often used with stringed instruments, including classic/acoustic guitars, violas, cellos, etc. and sometimes also as one of the options in electric guitars (usually in addition to a couple of single or humbucker pickups). Their defining characteristic being a very "flat" response curve (second only to optical pickups, and much cheaper), they're appreciated in classical music, where accurate timbre reproduction is favored over giving an instrument "more color".
What are the defining factors that would make such a microphone solution sub-optimal?
> Their defining characteristic being a very "flat" response curve (second only to optical pickups, and much cheaper), they're appreciated in classical music, where accurate timbre reproduction is favored over giving an instrument "more color".
I would heartily disagree. Every piezo pickup (undersaddle and body contact) I've ever used suffers from an inaccurate reproduction of the transients and over-emphasis of the midrange relative to the acoustic timbre of the instrument in question. Years ago the go-to solution to this was aggressive compression and parametric EQ - nowadays it's impulse responses. A microphone will always be more accurate relative to what's happening in the room. The problem is that microphones are less convenient than piezoelectric solutions because they suffer from bleed and can introduce feedback on loud stages.
Piezoelectric pickups are certainly more broadband than magnetic pickups as far as frequency response which makes them more ideal for post-processing but it's patently untrue that they're more accurate than a conventional microphone.