Guys, I did a side-by-side comparison of max and ultra myself. I was lucky today that the Ultra model was in stock in the apple store, so I bought it right away.
There is a clear difference in comparison, they both have a similar volume, but have different tones. the total decibels are similar, but Ultra has an overall smooth sound, but Max has a relatively high-pitched tone and has irregular frequency bands
Perhaps due to the material difference of the cooling system, the resonance sound is generated in the Max model.
I think this is why max users are a little more perceptive of fan noise. of course the Max is also incredibly quiet machine compared to other typical desktop PCs. However, if you want the same level of quietness as the previous m1-based models, I recommend buying the Ultra
I ended up spending $2k more than I expected, but I'm a very sensitive person so it's worth it for me