Service brake wail sound

My pete 337 is making a loud wail sound when you depress the brake pedal. Link to video below. It's as loud as a car horn, both inside the cab and out. Ive tried locating the sound with another person pressing the pedal, however the sound resonates against everything on the truck and its impossible to pinpoint, though it seems like it's front-end. Does anyone recognize this sound? Quick release valve maybe? (I can't even locate that, it's not on the front crossmember or anywhere forward of the front axle like id expect)

Tyia

https://youtube.com/shorts/6Ys-JJAr2Jc?feature=share

 

Makes the same noise regardless of parking brake set or released. All 4 chambers themselves are brand new but you're thinking maybe a line is leaking somewhere rather than a diaphragm in some valve or relay?