Tell tale heart how do you account for the police officers chatting calmly with the murderer instead of reacting to the sound that stirs the murderer into a frenzy?

Because the police officers do not hear the sound that is driving the murderer insane. Only the murderer can hear the sound because it's not originating from an external source but instead from in his mind. His is delusional, gone mad from guilt, from the crime he committed. The murderer is convinced that he can hear the heart beating from under the floor boards but it is all in his head. The police officers hear nothing so they are calm.

answer; ///attempts to change more than once behavior at the same time;

answer; independent variable;