In this project, you're going to create a VU meter using an Arduino. This is a fun project where the LEDs will light up according to the sound intensity. If you switch out the LEDs with transistors, you could control other things like light bulbs.
The sound sensor is a small module with a microphone, amplifier, and some small circuitry. It has two outputs; one digital and one analog output.
You're going to use the analog output. The analog output gives out a voltage between 0V and 5V that reflects the current sound level detected. By using this value, you can control how many LEDs to turn on for a given sound level.