athass_prkr
I don't understand how Tom can know someone is chasing him (at least until he enters the room when he senses the MC's modification). According to the functioning of the MC's listening power it is as if the sound of magic comes to him and he hears his music, it is not his ear that extends and touches the magic. It is a passive receptive sense, not an emitting sense. So how does Tom know the MC is looking for him? The MC only receives the magic emanations from the book, he does not force his magic on it to hear it.
athass_prkr:I don't want to spoil too much since I go into detail on how the chamber works later, but a core mechanic is the appropriation of the wards surrounding the entrance. So, that means that any magical event in the bathroom could be detected by its master, aka Tom. There's a whole thing about the impact of magical ownership and its effect on wards, but I don't want to start a magical theory lesson. Good question though.
Tom thinks he's so smart but... couldn't Harry just wait for him at the exit under his invisibility cloak when Tom comes out ? I mean, Tom is probably going to walk into the room more than once and even though Harry can't guess when Tom enters, thanks to the ward, he can position himself to intercept Tom when he exits. The cloak is an undetectable artifact and the map can keep Harry from getting tricked. Easy.