The "5.1" indicates a surround sound system that enhances the immersion. In a drama as tense as 13 Reasons Why , the 5.1 sound (used in official Netflix streaming) helps differentiate environmental noises, such as school hallway chatter, rain, or the cassette player's ambient sound, from the narration, enhancing the tension.
The dedicated center channel ensures that Hannah's narrative voiceovers remain perfectly audible over background music. 13 reasons why s01 720p hindi 51 english w link