Sounds like the anti-lock brake system. best to have a professional look at it.
The brake pedal vibrates.
Check for vacuum leak at brake booster
Sounds like a Vacuum leak in brake booster.
Most likely rotors are "out of round" and need to be either re-surfaced or replaced.
More than likely you have a warped disc brake rotor. Recommend seeing a mechanic for brake repair or replacement.
If the BRAKE PEDAL of your vehicle is vibrates, you need new brake pads or rotors, or both, and soon so you don't lose all brake power while you are driving.
Push down on the brake pedal and hold it there, do not pump.Apply the brakes in an even manner until the braking system starts to pulse and vibrates the brake peddle. This is how anti lock brakes tell you you are getting the most available braking from them.Keep enough pressure or force on the peddle until the vehicle comes to a stop.
A dashboard light appearing when brake pedal is depressed usually means brake fluid is low.
Most likely, this sound is coming from a vacuum leak in your brake servo, or brake booster. Which are usually located on the firewall, the wall that divides your engine compartment and cab.
THE BRAKE LIGHT IS LOCATED BELOW THE DASH. LOCATE THE ARM HOLDING THE BRAKE PEDAL AND YOU WILL SEE A SWITCH THAT COMES OUT WHEN THE PEDAL IS DEPRESSED TURNING THE LIGHT ON. WHEN THE BRAKE IS RELEASED THE SWITCH DEPRESSES AGAIN TURNING THE LIGHT OFF.
It is above the brake pedal not under it. Follow the brake pedal bracket all the way up and you will see the brake pedal switch.
make sure your brake pads are in good condition, a vibration in the brake pedal indicates a warped rotor to include worn front disk pads, make sure your front tires are not going bald, because they will do just as much vibration as a warped rotor when stepping on the brake pedal.