Chirping from engine at idle

[Higglypiff42]

I've had this chirping sound for a while now and I tried to ignore it but it's starting to annoy me. It's not very loud but it's loud enough to be obnoxious. It only happens at idle and up to about 2.5k rpms. It also only happens when the engine is warm. Also it doesn't matter if the clutch is engaged or not, the sound stays the same. It sounds like it's very rythmic and it gets faster as the rpms increase. Anyone have any idea what it could be?