I don't know what it is. But I love to hear the rain outside. There's a certain comfort in its sound. The way you hear it splash onto pavements, trickle off rooftops and slosh around off tires.
It fills a void. I am not normally someone afraid or uncomfortable with silence but I love the way the rain takes up the empty space. And when it stops [as it has been intermittedly today] I feel a little sad. Left alone with the silence, so quiet.