antilock brakes
There's nothing to fix, it's just there.
I like to test the antilocks once in a while (I had a Blazer fail emissions testing -believe it or not - because the antilocks had set a code when a wheel sensor lead was cut and the code wasn't reset after the repair). About testing;
My mail box is beyond a gravel patch next to a country black top road. I drive one side of the car onto the gravel at about 15mph and stomp the brakes. They slip a little, the antilocks groan, the brake pedal vibrates like crazy and the car stops quickly.
If you haven't felt the antilocks kick in, you should try it so you're not surprised when you really need them. It's a very strange sensation but if they're needed, the driver should just keep mashing the brakes and let the antilocks bring the car to a safe stop.
And you can compare the groan to what you're hearing (hope it's the same).