The noise level is less of a concern for me (the volume at least) it’s more about the frequency or sound itself. You ever hear those sounds that just bother your ear, and they sometimes are hard to locate? It’s like they become omnidirectional. Maybe this is at the edge of the human ear’s spectrum or something... kinda how a UV light bothers your eyes and can be disorienting at times.

For instance I have a Dell 2U server in my home office. It’s pretty quiet all things considered, but I wanted to lower the fan speeds manually (possible with ipmi tool) to make it quieter at the expense of maybe a warmer system. You’d think the lowest possible RPM would be best... but actually increasing it slightly from the baseline was the most pleasing sound, despite it being a tiny bit louder volume wise than the lowest RPM setting. At the absolute lowest speed the fans created this cacophony as they went in and out of sync, making a vibration sound. A little bit higher, that individual sound dissipated and I was left with soft white noise that was more enjoyable.

For heat pumps the noise rating is often published, and I would hope air conditioners are similar.

Purchase of consumer products is so difficult, especially with the huge variety of model numbers. Though I'm fairly unsatisfied with the latest iteration of Apple laptops, I do appreciated the very limited number of models, which at least allows fuller evaluation.

Umm, price aggregator sites around here show noise level in dB for a bunch of things (AC, fridges, washing machines, etc.). And I haven't been to appliance stores in the last ~10 years, but the detail sheet probably has the same information as the online version.