When my Central Air turns on the sound from the ducts just got significantly louder.

Question

Cold air is still blown out. The unit outside still apears to work right, no extra sounds. The area seems to be centralized in the ducts adjacent to the furnace by the air filter. Any ideas?

Answer 1

Check your blower, it is probably on the brink of a bearing going out, and when it does you will know for sure that it is out, because it will really make some noise.

Answer 2

Check your filter and check the blower motor for any potential problem.

Maybe something is in the blower wheel.

A motor ready to go out.