This is going to grow quite a lot as I get more of these written up. Thought I'd post the first few drafts to see what people think, where I can add more specificity or if there is a common portion that people think is missing
Quick comments because I'm likely to forget if I don't do it now. This isn't specifically aimed at
you, I just think these are important questions.
Blows up on destruction: Yes. Inconsequential.
BWAHAHAHA! Good one!
Effect: Emit a 20 kHz tone at 190 dB
Oh, it was 20kHz? We should bump this to 25 kHz so we can break ears without them being able to notice the sound. Try for our own version at the very least.
"Emit a tone at 190 dB" isn't really a well-defined thing, and more than "emit a heat at 300°C" is a well-defined thing. A 190 dB
point source has no volume at any positive distance, just like a 300°C point source has no heat. Sound is emitted from surfaces of a given area, and the volume drops off as the surface area grows, as long as it can be approximated as sphere-shaped, and you aren't going too far out.
If you emit sound from a 1m radius spherical shell, it's going to be 40 dB louder (10000x SPL) than if it was emitted from a 1cm radius shell at any distance ≥1m. You need to define a loudness at a
given distance, and only then can you derive the size of the source using basic math.
A mere 1cm radius shell would only sound like a 150 dB Earbuster at 1m distance, but whereas the 150 dB Earbuster (assuming similar 1cm radius source) will drop off to 130 dB the next meter in, the second meter would only reduce Jiraiya's from 150 dB to 144 dB.
This size pretty much matches your mechanics in dropoff, but it means the peak decibels are hard to hear unless you put it next to your ear or something stupid like that. But I'd expect a source large enough for those sorts of effects at close range are much louder than you gave at medium range. Note that sound attenuation at long distances varies a lot by frequency; a 20 kHz sound probably won't ever go further than 200m, but a 200 Hz sound could go 50km!
Secondly, that leaves a bunch of specific questions. Where is the emission from? Is it just from the surface of a sphere? Or the surface of the tag? Or the whole volume of a sphere? Is the sound a pure sine wave?─this affects whether it stacks. And if you overlap the producing volumes, does that stack, or is it like EM where it refuses to?
Personal suggestion: It emits from the whole volume of the sphere (because that makes the math easy), in an imperfect sine wave (because that reduces the need to care about interference effects), and stacks additively (because that's most intuitive).
Opponent Rolls an Athletics against the Infuser's Sealing to dodge (behind an obstacle) and take half-damage.
This seems like an odd choice. It travels at the speed of sound, and you'd need to know what it does ahead of time to make the right kind of dodge. Assuming the team is wearing protection, a basic technique is to trigger it while holding it, which should basically be undodgeable. I don't get where the infuser's sealing comes into the picture.
At creation time you choose a level of sound-dampening. When activated the seal dampens air vibration within ~2cm of itself. It is useful against loud noises and sound-based (nin/gen)jutsu.
Is the attenuation permanent? As in, is the sound restored when it leaves the area under effect?