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Comment by bitdivision | Hacker News Reader

I just tried this with a mug of coffee in an ultrasonic cleaner. Left it running for about 5 minutes with room temp water and ground coffee in the mug.

Compared afterwards to a mug left outside the ultrasonic cleaner. There was definitely more extraction in the ultrasonic cleaner, though the coffee was still fairly weak. Likely needs more time given that they are using a custom horn etc.

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Thanks for the test.

They also use 100W of ultrasonic power: https://www.sciencedirect.com/science/article/pii/S135041772... and a cursory search says this is the domain of more expensive ultrasonic cleaners (> 100$).

True, the one I have was a China special, but does say 60W.

Supposedly ultrasonic cleaners use 15-400 khz, and DML audio exciter drivers go to 17-20 khz, so you could theoretically grab a few of those for under $100 and have at it with a sine generator.

The transducers are fairly cheap from China [0]. I've thought about making a high powered bath before but never pulled the trigger.

0: https://www.aliexpress.com/w/wholesale-ultrasound-transducer...

Ah right, yeah those would be perfect.

I would imagine there needs to be direct coupling between the transducer and the container holding the coffee, the water layer likely doesn't transfer nearly as much.

Probably best to just get a stainless cup, glue the transducer(s) to it and let it rip.

Water is incredibly efficient at transmitting sound.

Doesn't mean the cup is any good at absorbing it.

The mug will attenuate almost all the signal. Maybe try with a disposable plastic cup?

I'll try it another day, the cleaner is packed away now.

Perhaps a ziplock bag would work well.

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