The Bad Son - S8-E3
Audio problem: Frasier is standing in his living room talking to Niles. We hear a knocking or tapping. As Frasier is expecting his date, Miranda, this might make sense, but they do not seem to hear it and make no move towards the door. A short time later the doorbell rings and Frasier's date arrives.
Answer: In the last episode, they explained that Tossed Salad and Scrambled Eggs is a metaphor for the mixed-up people to whom Frasier dispenses his radio psychiatric advice.