noise sound

First time owning a jeep wrangler and just curious if the noise I hear when pressing down on the brake is normal. It sounds like air is leaking out when the brake is pressed. I got it checked out at a local service center and they stated they couldn't find anything wrong but the place didnt...

Little Help?? Hoping someone can recognize the noise/sound. Happens when I'm at 25-30mph barely on the gas... not accelerating. 4.0 with automatic. 36k original miles on an 06 TJ. thanks in Advance!!