The noise you hear is being caused by a flame lighting at the tip of the burner orifice, before the gas gets to the burner assembly. It acts and looks like a blow torch. This can be eliminated by cleaning the soot from the inside of the burner assembly, and, if needed, proper adjustment of the burner's air shutter.
If my answer helps you, please click on the 'accept' button. That's how we experts are paid for our efforts.