The past couple times I've been on the interstate, I've noticed a strange metallic ringing sound, somewhat high pitched, seeming like it's coming from the engine bay, although it may be part of the exhaust. It sounds as if some part(s) are reaching resonance, as it only occurs at certain rpm, most noticably at around 3200, with quieter rings at ~2500 and ~4100 rpm. It is also only audible at or near WOT, and can be heard in all gears at said engine speeds, although it's harder to catch in first or second. Engine's a D16Y8 with basic bolt ons, 43k miles, no work done other than regular oil changes. Could this be related to the ticking sound I hear between 1500-3500 rpm? Would a valve adjustment do any good? I'm really just looking for ideas as to what may be making this noise.

 

Valve adjustment might help, can't hurt, & you're probably due for one anyway.

But your description sounds more like a loose heatshield on your exhaust.