Putting my phone in the front of the Mac Studio, I got 29 dB. At the top in the fan wind (which is probably causing wind to go around the microphone and create more noise) it was 36 dB. Immediately above where the fans are (top of the Mac Studio, but toward the back), it was 32 dB.
Mine is mounted to the back of the footwell area of my desk. When I sat my phone on my desk, it was registering 28 dB. It's far from silent, but it's not a distraction for me except when nothing is going on in the room. I usually get used to it pretty easily unless I'm focusing on it (this thread makes me focus on it).
Despite all this, it's not dead silent even at 29 dB. I have a slight hearing deficit from working on helicopters many years ago, and even with my slight deficit I can hear it.
As I said in a previous post, it's about the volume of somebody whispering. By comparison, when I print from my Brother MFC-L8900CDW laser printer, the printer registers at 52 dB. When my HVAC unit is running, it's registering 40-45 dB.
I'm using the NIOSH Sound Level Meter app with the iPhone 11 Pro's built-in microphone. I know it's not calibrated nor the most technical, but just to give you some comparison.