Hi @AndrewN,

Welcome to the Dyson Community!

The quietest fan in our range is our new Dyson Purifier Big+Quiet Formaldehyde. Take a look at our website to learn more about this here.

A Helmholtz resonator and optimised blade geometry minimise the aero-acoustic noise. Broadband noise is further attenuated by the microporous material along the flow path. Vibration is isolated with a rubber mount. So, the little noise you do hear, is of higher sound quality. PET fibre mesh breaks down turbulence to suppress flow noise while delivering a smooth powerful airflow and refined 360 inlet geometry minimises air leakage while ensuring a quiet, energy-efficient compressor. Finally, our engineers stripped out every component and optimised each, until the air purifier emitted as little sound as possible.

Hope this helps, but let us know if you have any other questions!