Noise From Engine Bay?

[KLR32R]

Hey guys, I have a problem with one of my daily cars.

It’s a 99 mod toyota corolla no engine mods besides exhaust. The problem is, when driving and reaching 3500rpm it makes a sound like a grind / fast vibrating noise, somewhat similar to when your brake pads are low and grinding although the sound only happens for like 1 second. This happens in all gears (have not tried 5th obviously). The noise sounds like its coming from somewhere in the top of the engine bay but I cant be sure. Ive been told to check is the dipstick as it could be loose or in the wrong way , and to check nothing is loose around the brakes area. The car doesnt lack in power and is driving normally.

So before I take it in to the mechanic does anyone have any ideas what it could be?

Any help is appreciated cheers!