I thought that I understood toilets but this one is driving me crazy. Scenario: 2nd floor master toilet room, floating cup ballcock, tank filling and draining properly with no obstructions, bowl draining properly with no obstructions or unusual slowness. Concern: during the refill process, a trickling sound of water dripping rapidly atop standing water is heard from somewhere inside the bowl’s interior, and continues for approx. 5 seconds after the refill process is completed. ALSO, from the downstairs kitchen, and directly below the toilet room in question, the aftermath 5 second tricking is heard within the walls infering that we either have water falling down the drain pipe onto standing water and is therefore amplified through the structure. I’m about to rip the toilet out to conduct an indepth search and snaking effort, so any input would be helpful.