The sound goes like "whoo" and gets louder. When I

take it to an accredited service shop that has experience on your make of vehicle , have it road tested and get a quote for repairs
your description of the noise is very vague to say the least so you need a proper diagnosis before it gets dangerous

suspect it is warped disc rotors. If the pedal pulsates under your foot on light braking I would take it to a brake shop for investigation of the fault. Any noise or unusual incidents with brakes can become critical if ignored.

Brake switch is designed to shut cruise off when brake pedal applied, sounds like a defective brake switch, because when she applied the brakes it's supposed to cut power to cruise module, so either that is problem or your throttle cable had iced up and or both

Hi Wisker, If the brake problem occurs once you have been out on the highway and applied the brakes several times, the problem is with the brake master cylinder and is associated to the seal which should allow brake fluid to return to the pot when the brakes are released. It would seem that your vehicle is building up fluid pressure which is not returning and causing the bakes to apply from that point onward. When the fault reoccurs near home, drive there and open one of the bleed nipples and the brakes should return to normal until they are applied three or four times. The cure is for you to replace the master brake cylinder. Once done bleed the brakes, beginning with the wheel furthest from the reservoir and work closer one wheel at a time untill you complete all four. Make sure the brake fluid is kept topped up all the time and the wheels are chocked so the car cannot move. The Caddy is heavy and you don't want it resting on your chest! regards John

built into the brake pads is a small bit of metal that when the pads get to low to be safe , runs on the rotor and produces the squeal applying the brakes stops the vibration so the noise drops off

you sure it's not the brakes? Also sounds like it could be the axle assembly. If it "is" the transmission I don't know of any magic solution only the mechanic could put in. I've used Lucas Transmission Fix before if they aren't too bad and it can work (at least long enough to sell it or even better trade it in). You just put it in where you put your transmission fluid. It's pretty thick so make sure your fluid input is easy to get to or get a funnel with a very long tube on it. If you haven't changed our brakes for a while take one of your front wheels off (try to see if it's louder on one side) and see if the brake pads are down to bare metal. Also look around for other reasons while you have your wheel off. Good luck.
If this helps you resolve your problem, please
consider giving me a good rating and a quick
thanks or good job.It will help me as well.
Thank you.

most probably your brake pads are on the warnning tabs, get them checked

It sounds like pads against the rotors. Does it get louder or stop when applying the brakes?May be a stone or maybe just rust or maybe you need brakes looked at.

take the wheel and drum off the back and check that the shoes are not worn out on the edges..what happens is the end wears off first but as pressure is applied the shoe moves to where there is some pad left..severe brake dust can do it too. get the brakes checked as soon as you can.to clean and adjust the rear brakes is not that expensive.

from my experience its sounds like ur front rotors may need resurfaceing...if ur doing that...may as well replace the brakes on the front as well...sometimes glazed front brake pads may make a sound but never heard of it as a grind, usually its a squeal...have ur dealer check ur rotors for hot spots in which u would need them replaced if they are overheated..also check the front pads for cracked brake pad material