Help with pathway light transformer buzzing
Most of these types of transformers have an audible buzz, from my experience. Assuming your tranformer is nothing more than one of those found at the typical home improvement store, I would be tempted to replace it you believe the buzz is unusually high. If you are staying with incandescent, try another one like it.
I don't believe I would replace lamps with LED without also replacing the transformer type. I would replace it with a regulated power supply to best ensure voltage stays within a prescribed range regardless of load. This is, by the way, the approach I took. My power supplies now are all inside and make no noise that I can hear.