I came to the conclusion this morning that I should not listen to potentially comical things on my iPod while riding the Metro.

If you have never been to Washington, D.C., let me try to characterize the atmosphere on a Metro train. Unless you are sitting next to someone you know, there’s a good chance you are sitting in silence. That may be while listening to an iPod or reading a book, or just staring at some nebulous space in the front of the car.

During rush hour, when the trains are full of commuters, the silence can seem magnified.

So imagine the scene as I step onto a packed morning train. White headphones are pressed into my ears. A podcast that began playing as I waited on the platform is the soundtrack to my ride home.

The faces around me are checked out — a semi-catatonic state brought on by the morning commute. The only sound they hear are the wheels grinding along the tracks and the occasional garbled station names being blasted out over the loudspeaker. I can hear a little of that too through the headphones, but mostly I am lost in some piece of radio magic. Fortunately, I get off at the end of the line, so I don’t have to pay the least bit of attention as the stops go by.

And then it happens. There’s a joke, a humorous comment, a funny aside. I am about to draw the attention of those around me who are even half awake. The joke moves through my ears and into my brain. It is processed. The humor reactors are put on notice. A pulse of instructions runs to my face. The brain wants to laugh.

But wait, there’s another emergency instruction. Another part of the brain is ordering an override of the laugh instruction.

“NO NO NO! Abort!”

It is too late. I do my best to hold my mouth shut — teeth clenched, trying in vain to suppress the overwhelming smile and the urge to chuckle.

The morning silence broken, there is only one thing I can do: Look out the window as if to say, “There’s nothing to see here.”