What's this noise??
 

When I'm driving i can hear this buzzing noise coming from the front wheels.The noise comes and goes. It is really loud and annoying. It is clearest when braking. I recently had both cv axles replaced twice at the dealer. The first time they were replaced they installed something incorrectly that they fixed the second time. After taking it to the shop for the third time Friday the technician told me they couldn't hear the noise because it was raining and that it was most likely tire noise. I'm not a certified mechanic but I seriously doubt that its the tires, otherwise I would hear the noise constantly.I have a six month warranty on the axles which runs out in August. Any ideas would be appreciated.