I used to have a Daz one that used to drive me nuts with it's constant whistling. I accidentally broke it during maintenance , but I have now reconfigured my set up and deliver my CO2 via the return pipe from one of my filters, much quieter now (and more efficient )
I've found they always chirped. I've only got unbranded diffusers (sold as Rhinox I think). It's not loud, but I have two tanks in my bedroom. I kept the glass diffuser on the main tank, on which the CO2 is turned off at night by a solenoid, and went back to using a Hagen ladder on the tank that has 24 hour (yeast) CO2.
It's just a choice. I can't hear mine in the day, it's only when the room is quiet at night that I noticed it in the first place.