Beep sound when shifting to park

Hello All,

I have a 2015 L model that I purchased several months ago. I have noticed at times that when I stop and shift from drive to park, I hear a beep. I dont hear it every time but usually have my music on so may not hear it those times. I was wondering if this is normal or cause for concern. It is a base model so doesn't have any kind of reverse camera or anything that should sound a warning. Also, there has been nothing behind the car when it has happened. Has anyone else heard a beep while shifting to park?

I called my dealership and the man I talked to said he'd never heard of it before and would have to listen to it himself. I will bring it in to them next week and hope it will do it for them and will also listen each time I shift between now and then to see when it does it but wondered if anyone else has experienced this with their Corolla.
jolly, I'm wondering now if it does have something to do with the doors locking and unlocking when shifting in and out of park. But it doesn't do it each time and it's one beep. My brother has a Tundra and it's the same beep that he gets when he locks/unlocks his truck with his key fob, except his beeps twice. My car didn't come with a key fob and they said it's not set up for keyless entry. It doesn't do it when I use the key to lock/unlock. Hopefully the service department can figure it out.