sox

I’m writing a script that uses sox to record me talking.
Now I need sox to wait until it detects sound before it begins recording, and I do have that figured out. But I also need sox to exit once there has been silence for at least 3 seconds.
As it is now, I have to manually kill sox once I finish talking, otherwise sox just waits again until I talk some more, appending to the output file (That’s not what I want).
Here is the command for recording I am using now: