The answer to 'why is my recessed lighting buzzing noise' is that a buzzing or humming sound from recessed lighting is usually caused by a faulty or loose electrical component. This could be due to a problem with the transformer, ballast, or wiring connections. The buzzing noise may also be caused by interference from other electrical devices in the home.
To troubleshoot the issue, first check that all the light fixtures are properly installed and the connections are secure. You can also try replacing the bulb or ballast to see if that resolves the problem. However, if the buzzing persists, it's best to call in a licensed electrician to diagnose and fix the issue, as they can safely inspect the electrical system and make any necessary repairs.