If you take a snapshot of train chatter you’d see that it gradually rises from the morning on, peaking in the evening. Even the uptick in sound between 7 and 8AM is noticeable.
People care less about you and more about their own privacy in the morning. Direct conversations are virtually disallowed, as are phone calls. Texting is the preferred method of all interaction.
The most significant noise makers in the mornings are the squealing and grinding of the train tracks competing against the loud overhead fans.
As the afternoon approaches the train gathers less people but louder mouths. Feet make their way on the seats. Cell phones ring. Headphone music gets louder. Laissez-faire defines the afternoon.
The evening, especially Friday evening, is a bit of a free for all. The work stops, the drinks pop, the mobile fingers get more aggressive as people respond across social networks and like everything in their feed. Everyone knows each other’s weekend plans.
People unwind as the days lives on; the rules get looser with time. Life resets daily with the emergence of noise.