Change in engine pitch

I’ve noticed this past week that the engine of my '99 Nissan Altima has started running at a higher pitch than it used to. The RPMs appear to be normal, but the pitch of the engine seems to be higher. Is this something to be concerned about?

Use a mechanic"s stethoscope (or improvise with a long screwdriver) to listen for noises from engine driven accesories.See if you can influence the noise by hard turns (loading the wheel bearings).Make sure fluid levels in transmission are corect.What’s the mileage,could it be time to expect a drive train component failure?

Check the windows.