The partitioned room I rented had such poor soundproofing that I could hear the neighbor's alarm clock.

Every morning, the neighbor set six alarms, ringing from 6:30 to 7:00, but none of them woke him up.
It was me who woke up instead.
Later, I developed a habit.
Every time the alarm rang the first time, I would knock on the wall.
Three knocks, and the neighbor would shout, "Got it." Then the world would be quiet for ten minutes.
One day, he moved out.
The next morning at 6:30, the alarm didn't go off.
I woke up, lying in bed, hearing my own heartbeat.
It was too quiet, so quiet I couldn't fall asleep.
I went to knock on the empty wall next door.
Knocked three times.
No one shouted.
I lowered my hand.
That evening after work, the new neighbor moved in.
It was a girl.
When I passed by her door, she was reaching inside.
A kettle, a small desk lamp, and an alarm clock.
Not a phone alarm.
It was an old-fashioned one, with two iron bells.
I stopped.
She looked up at me.
I said, "Can you knock on my wall when your alarm rings?"
She hesitated for a moment.
Then she said, "Okay. But I can't get up. You knock for me."
She had been living there for three months.
Every morning at 6:30, when her alarm first rang, I knocked three times on the wall.
She would reply with three knocks.
Then we would get up separately.
We never met.
We didn't know each other's names.
But for the first time, I felt that in this city, a partitioned room can't block out a clock.