Cheap ultrasonic cleaner

[Turnup]

Ah, I see. Must be very short pulses of ultrasonic then!

Mine sounds like 50 or 100 pulses per second. This probably reduces the heat build up in the transducer and drive electronics cos they're doing less work

[Solvo]

The loud buzz is usually because the Ultrasound driver fire at about 25Khz which itself is silent, but the vibration it creates in the metal tank results in a lot of harmonic resonance - visible as ripples on the surface of the water.
If you look at the edges of the tank you'll likely find a dense rubbery seal which helps to dampen the harmonics.
Larger machines are still unpleasant to be around though. Sadly the really quiet machines are incredibly expensive as they operate at far higher frequencies.

[andrew375]

Aldi currently have a small us cleaner for £19.