This sound sensor is adjustable so you can tune how loud the sound has to be to trigger it. Note that this is not a microphone that you could really use to do sound processing, its purpose is to detect a sound over a certain loudness level.
Using with Arduino
You would attach this sensor's output (signal) pin to a digital IO port. When you read the port, if sound is being detected the port will be HIGH.
Because soundwaves constantly change, you might want to poll the port a bunch of times, for a few milliseconds, so you don't just happen to read the port when the soundwave happens to be low.
Another strategy is to put the output of this sensor on a digital IO pin that supports interupts, and create an interupt routine that logs the time (using millis() clock) when sound was last detected.
There are numerous tutorials on the Internet regarding strategies to use this sensor, so explore!