Xi'an Metro Line 2, evening rush hour.
Chen Mo leaned against the connection between the carriages, Bach's "Aria on the G String" playing in his headphones. Music is like water, but it is not meant to cultivate sentiments - after the accident three years ago, 60% of his left ear's hearing was permanently damaged. High-frequency audio and images were covered with a layer of frosted glass, while low-frequency sounds had the texture of metal friction. Classical music is the closest sound template he can find to "normal". Two hours of training every day is to allow the brain to recalibrate its perception of reality.
But what he trained was not "hearing clearly", but "hearing wrongly".
"The station ahead is Bell Tower Station. Passengers getting off the train please prepare in advance."
The female radio voice has a clear accent. Chen Mo frowned slightly.
The seventh time. Starting from Yongning Gate Station, every time the station is announced, the pitch of the word "please" is 1.5 Cents higher than the standard announcement. Ordinary people can't hear it, but for a former psychoanalyst like him who needs to rely on the details of sounds for behavioral profiling, it's as dazzling as an ink dot on a white paper.
He took off his right earphone.
Noise suddenly flooded into the carriage: the whispers of student couples, the playback of short videos by middle-aged men, and the creaking of the pulley wheels rubbing against the ground. But beneath these sounds, there is a lower frequency vibrating.
It's a vent.
The ventilation system of the subway tunnel has a fixed frequency. Chen Mo has been riding this line for three years and can draw its sound wave diagram with his eyes closed. But now, the sound of airflow coming from the top of the car is reversing its phase once a minute.
It's like something is "breathing".
