High pitched noise driver side, engine bay

I have a high pitched noise coming from the driver side of the engine bay. I’m writing to see if anyone has ideas or past experience regarding a potential source. The noise is typically heard in park or neutral after the engine is up to temperature. The noise stops when I shift into drive or reverse, and starts up once I’m moving again and coasting around. I recently took it in for diagnostics but the sound could not be reproduced. I also just replaced the belt and idler pulleys with no apparent change. I’d appreciate any insight here. Thanks

 

From my experience a high pitch whine like that means your alternator is starting to fail. Have it tested.