cats do the darndest things

I've had Mecrutio since he was about 8 weeks old. At some point, this giant cat could curl up in the palms of my hands. Now, not so much. The point is, I've had him since he was very young, and in this time, we have never lived in a house that has a doorbell. 

Why is this relevant to anything? 

Because we have recently discovered that Mecru reacts very strongly to the sound of a doorbell. I think it started with one on tv or something, but now a certain boy likes to load the sound file on his computer and play it at random times. The cat's ears go backwards, and he takes off running. He doesn't run to the door. In fact, he doesn't have a set place that he runs to. He just runs. Then waits expectantly for something to happen. Is he waiting for someone to come inside the house? I don't know. I don't know why he would, since we've never lived somewhere with a doorbell. 

It's mildly amusing, but I really really want to know the logic behind it (even if it's cat logic).