Light roar coming from AC/Heat

There seems to be a small roar coming from my AC/Heat. The roar gets louder when I turn the speed up from 1 to 4 on the speed control. Takes some time for the heat to get hot as well, but I assumed it was my thermostat. Any insight would be great. Thanks.

Please take to a reliable shop in your area as trying to diagnose sounds over the net is very difficult.