Does anyone know what this noise is when I'm bleeding the brakes? Car is a 2008 TL Type-S. It has done it every time I've bled the brakes since I bought the car, seems to be coming from the master cylinder/brake booster area. Makes the noise when the bleeder is open on any caliper and the brake pedal is being pressed down. I can feel the vacuum line from the booster vibrating when it makes the noise.

No clue what it is. Attached a link to a video I uploaded of the noise I'm referring to. Any help is greatly appreciated.

https://youtube.com/shorts/9bwQqSLhuVw?si=l0uBDZgShDVjzu0l