The only area I've heard people talk a lot about knife sounds is with the balisong crowd. They can be picky about how the knives sound as they're being flipped around, particularly whether or not they "ring" as a result of the parts being machined in a way that causes them to resonate like tuning forks.
Personally, I notice when a knife sounds different but it wouldn't be the deciding factor whether I keep it or not. The sound can be affected by a lot of things like the locking mechanism, detent, construction of the knife, etc. Some of the more notable ones in my collection are:
Pohl Force Mike One: This one has a particularly solid and damp thwack. My theory is that it's because the teflon washers don't scrape, the titanium on steel lock seizes up solid, and nothing on the knife rattles. The fasteners are wedged so tightly into the handle that it's a royal pain in the ass to take apart, but it does dampen the sound enough to make the knife seem more solid.
CRK Umnumzaan: Super quiet because of the o-rings on the blade stops and the oversized ceramic ball interface.
Spyderco Phoenix: Next quietest after the Umnumzaan; the ball lock engages quietly and instead of a stop pin you have two solid titanium surfaces come together.
Maxace Sandstorm: Despite being an oversized and overbuilt knife, the sound it makes isn't the most reassuring. It has an extra hole in the blade that you can stick a pin into when open to serve as a secondary lock. When opening and closing the blade, the detent clatters across this hole in addition to the detent hold and lock face. Instead of a solid, singular thwack, you get something that sounds kind of like a quick, hollow rattle. It doesn't detract from the knife functionally, though.
Cold Steel Espada Large (aluminum): This one I think has the most impressive thwack in my entire collection. The knife is built very solid with no rattle, and the large black has a lot of inertia hitting the stop pin. But the biggest difference compared with my other Tri-Ad locks is the stiffness of the spring. It's stiffer even than the Rajah II, which is a bigger knife. That means that when the lockbar falls into the blade, it does it with more of a bang than any of the others I've tried.
My Axial Shift is probably the worst, very audible "ting."
That's funny, I kind of like the sound the Shift makes, reminds me of the hammer dropping on a revolver. I prefer it over the sound my Hogue Incursions make, since they have the distinct tone of metal surfaces scraping over each other (possibly due to tighter tolerances since they have less play than the Axial).
That's my first thought
