I think this model has flame rod in it down the burner tube. these burners have been updated to pick up combustion air. These flame rods have to be properly adjusted as to not miss fire. If out of adjustment or worn they will sound like h##l. Also the it sound fire up into high burn after pilot with out lag. if that is correct you may have air screen on blower out of adjustment or dirty.
I think this model sets like the vhx 24g. If the unit has the new style combustion proving switch that is sensing on the manifold. the rod has a cord grip holding it in the burner. From tip of spark plug tip to end of the cord grip it is 1 1/8- 1 3/4. Put a mark on porcelain fire unit if it don't clean fire rotate rod retry. make sure the rod is clean. They are terrible about fouling. Also make sure the ground wire is good to burner and the grounding tit is clean on air screen on the end of burner.