I just bought a new Venue and I was wondering what’s the sound you hear under the hood when the engine turns off? It lasts for about 5-10 seconds.

 

Don't know without checking, but some alternators have pulleys with various style engagement systems like over running clutch pulleys for example . The system prevents excessive belt wear and saves component parts. If you can why not have the dealership or good shop just listen to the sounds and maybe they can provide some relief of your concerns.