Another noise thread.. My prius barks at me

So I've had my Prius for a while now and i have just started noticing a new noise. i am pretty sure it wasn't there before and that i would've noticed it if i had heard it when i first got it.

My Prius sometimes makes an odd faint barking/chirping sound when i let off the breaks. the sound comes from outside the car. sometimes it seems to happen randomly when i apply the breaks too. The sound almost sounds like some other driver chirped their horn or beeped their horn for less than a second. When i first started hearing this noise both the wife and i thought it was actually impatient drivers beeping at me.

is this something i need to have looked at? I just went over my 30k mark so the warrantee is up. if i don't have to take this into the dealer then i don't want to. anyone know what this could be?

 

thanks for the link sorry for dupe thread i did a search on prius noises and didnt find those threads.