One of these devices used was the manipulation of sound. This is used, for example, in the famous shower scene. During the entire scene, there is little to no music, and only the diegetic sound of the shower and the woman's actions are heard. This draws the viewer into almost a false security, as there so far is no reason for us to be suspicious. Later on in the same scene, we see a figure through the shower curtain enter the room. This is accompanied by a very faint, sinister piece of music. The viewer then realises that this character means to harm the woman, or is at least shrouded by danger. Within roughly 7-8 seconds, this sense is confirmed, as we see the figure pull open the shower curtain and, in the story, violently stabs the woman to death.
In order to increase this sense of danger, the moment that the curtain is pulled open the audience hears a non-diegetic screech almost, and the near deafening cry only enhances the danger that is given to the scene, as the loud noise alarms the audience greatly, and implies how scared and doomed the woman is. After the attack, the sound of a low instrument is heard as the woman struggles and attempts to cling onto life. This is noise is the result of the murder, much like how the woman's dying moments are a result of the attack. This could imply that the sound in the scene represents more than just a musical accompaniment, but more as a sign of her own life.
Psycho is also a host to a number of different thriller conventions, such as Levi Strauss' theory of Binary opposites. These opposites are shown throughout the film, and these are shown very appropriately, and yet, sometimes confusingly. This is shown in the presentation of Good vs. Evil. This is due to the confusion that is given to the true identity of the villain, as during the film we are told that the killer is Norman's Mother. Therefore, the audience gets a sense that the mother is the evil, and yet we don't prescribe a specific character the role of a Hero. This role is later given to the sister of the woman that was murdered, and just as we can finally assign the roles to people, Hitchcock decides to confuse us and to make Norman the villain under the alias and the identity of his mother, and we learn that our hate was mis directed.
