You can connect the Voltage connector to the 3V over the 5V and run the fan at a slower speed and less noise. It will ramp into use for longer, but the noise difference is worth it and case of you will certainly not notice it's activity as much.

Been nice if they just had the fan and connector attached to a new top for the case and could of added some side vents with height, making things just that much easier overall.

I myself have a 3rd party acrylic layer stack affair with a top fan and heat sink with 3V and run it constant as well below whisper level. I'd measure the dB but other systems currently mean my noise floor is 50dB and with sound meter right next to it, I get nothing above that. Though when just that a running, it a faint breeze sound at best.