How Did Alfred Hitchcock Build Suspense In Psycho

Alfred Hitchcock's powerful, complex psychological thriller, Psycho (1960) is the "mother" of all modern horror suspense films - it single-handedly ushered in an era of inferior screen 'slashers' with blood-letting and graphic, shocking and killings. While this was Hitchcock's first real horror film, he was mistakenly labeled as a horror film director ever since he directed Psycho.
The master of suspense skillfully handle and guides the audience into identifying with the main character, luckless victim Marion, and then with that character's murderer named Norman.
When the shower scene starts in the film, the scene starts with the peaceful equilibrium: there is a noticeable lack of sound, as the shower turns on, we hear the continuous pattering of water in the bathroom, which gives us a clear understand that the female character is going to have difficulty in hearing
anything as the sound of shower sinks out other diegetic sounds which the character can hear, in the plot of shower scene, then, when Marion appears to be uncovered in the scene of shower is because, the director wants to convey a message to audience by showing the facial expression which she acts out in the scene.
Facial expression-
Closed eyes
Enjoying the shower
Feeling relaxed
And, when the silhouette of Norman gets clearer the tension in the scene gets scarier.
So the director wanted to both the scene showing how Marion is relaxed and enjoying her shower but at the same time the tension was being created as soon as the silhouette of Norman was shown to keep the suspense and the tension going on,
As the shower turns on we can hear the constant pattering of water but except of that no sound can be heard. If the shower was turned off, she might have heard Norman coming inside the room by hearing the nob sound, and she could have prevented herself from the murder, but only if she had not taken a relaxed shower. So that explains that Marion didn’t have any doubt or idea about Norman being the murderer of her life.
The character appears to be completely oblivious to the world around her, as seems through the use of her facial expression, her facial expression and appearance of her body makes the audience see her mood and feeling in that scene that she is relaxed and tension free in the scene, but to also keep the tension going on the silhouette of Norman was
shown.
As Norman pulls back the curtains and attacks Marion with a knife, it get the tension higher as the sound of her voice goes till the high pitch, which signifies the sharpness of the knife and the horror murder which was happening during the scene, the change in the sound occurs when the Marion is murdered and slides down the floor, The sound changes from high-pitched screeching to a low-pitched and disturbing sound is because to signify the silence and sorrow moment but also to keep horror going on, and that is how Hitchcock's powerful, complex psychological thriller suspense in the film is convayed to the audience so successfully.