I did a search on ABS brakes but didn't find the answer I was looking for.

When my ABS kicks in there is a fairly loud noise that comes from the front of the truck. Almost like a buzzing/hissing noise. Is this normal and what is it?

I had ABS on my Ford Bronco II and never had this noise.

 

The ABS modulator is on the drivers side fender under the hood. It's makin all the noise, and from what i understand it's normal/