Started up the car this morning, got out of the car and it was buzzing loudly. I normally just start and go so I may not have heard it before. Frequency didn't go up with engine speed. Checked under the hood, it's loudest near the air box/transmission stick, but I suspect it's the alternator. The alt is only a few weeks old. It went away after about 1 mile. Could it be the alt across the engine bay? There's nothing by the air box I could tell that would buzz.

 

could be the hood? the fenders? while its buzzing next time just start touching parts and see if it stops.

 

Maybe headlight wiper motor is bad? If you have one.

 

Didn't sound like sheetmetal, but if it does it again tomorrow I'll feel around with my hand. It's like the high voltage power line buzz or hum.