They make ultrasonic jewelry cleaners for $75 that should work just fine. You're referencing something that is intended to be used with hundreds of gallons of water.

I'm just talking about the paper. If they had referenced what you mention I would have referenced that

Also it will be punishing for pets and MEMs microphones.

It's a prototype.

What? I went on Aliexpress and found a 40KHz transducer for $40. You can 3D print the attachment, can't you?

A woofer from AliExpress is not a speaker with amp you can use for University level audio work.

I expect they used something like these:

https://www.emerson.com/en-us/automation/branson

You cannot 3d print anything in the ultrasonic chain, they need to be machined from specific metal, that's why the horns cost so much.

I looked up "transducer" and it seems to be what you'd need. But! You seem to have found where I was wrong: the horn. The horn seems to be the actual expensive part here. They could start a business I guess selling these en-masse. If anyone has any ideas how a maker could create this within reason please reply.

You can't really sell them in big quantities because they're typically custom to the task. They need to be custom shaped for each application.

Portafilters are made in mass so you could make horns for common portafilters.

> A woofer from AliExpress is not a speaker with amp you can use for University level audio work.

We're talking about coffee here...

Exactly!

Wars have been fought over coffee, people regularly spend thousands for coffee machines. There are entire companies that exist just to cater to this market.

Me, I'm a tea guy.

A wholly different set of wars