Place it at the cut between the normal location and the liminal one, after a door knocking sound builds the approach and before a classic error sound sells the glitch, then let the next scene continue without another effect for a while.
About this sound
This seven-second clip captures a reality failure as the space slips into the Backrooms, built from a low ambient hum and distorted transition tone. It feels quietly unsettling and disorienting, like stepping through a wall into an empty, fluorescent liminal place that should not exist. It comes from Backrooms lore about falling out of ordinary reality.