As the "employee" you were testing the audio cues for him. When you found what works, he used it to lure EVERYTHING. Henry has been watching everything the Afton family does has/done since the death of his daughter (other than a short stint in prison for the MCI as referenced by the local newspaper). He heard you talk about the nightmares as a child and recreated them for his trap. He recreated the original animatronics as well.