My 2006 Toyota Corolla makes noise when braking

My 2006 Toyota Corolla Sport makes a “wha wha wha” noise when I’m slowing the car down and coming to a full stop. Once I press on the brake it squeeks (as if the brakes were not in good condition). I replaced the brakes the tires, the brake fluid. The dealer and an independent mechanic said the car is OK. The ind mech. said that the caliper something or other on this model is different and the noise is normal. I just can’t believe that though. I think the noise is greater when the car is at a downhill angle ot slight dip and its slowing down.

Does the car shudder while braking, especially at highway speeds? Does it pull to one side, either while braking or driving? If neither, I guess the brakes are not dangerous, but neither was the work performed up to standard.
I would guess that the “wah wah” sound is from the brake pads on one of your wheels rubbing against the rotor during normal driving. The reason it seems louder while slowing down (until you brake) or while driving downhill is that engine noise is masking the sound until you let off the gas. The squeaking noise is due to brake dust build-up while driving, which is dissipated when you hit the brakes, but first makes a squeaking sound. You have a rotor that is less than perfect and possibly a sticky caliper.

I have to wonder why the brake fluid was replaced in a four year old car? Did the fluid leak out? Were you given any reason for the replacement?
I think the next time you need new pads will be quite a bit sooner than the first time, and you should let someone else do it next time. Ask around for a better mechanic.