1. Events
The brown events block in Scratch starts script's when certain things happen. For example, when the user presses a key, clicks sprites, or uses a webcam or microphone.

2. What are Clicking Events?

3. What are Key Press Events?

4. Sound Events
Using a microphone, sprite can detect how loud sounds in a room are on a scale of 0 (very quite) to 100 (very loud). “when loudness >10” block to make a script start when the sound is loud enough.

5. Sound Event
Start a new project, and add the “room 3” backdrop image from the backdrop library. Drag the cat sprite on to the chair and add the script shown here:

6. Sound Continued
Shout into the microphone – the cat should jump out of its seat with a fright and meow.

7. What are Webcam Motion Detectors?
Webcams can be used in Scratch 2.0. Add this script to the cat, and when you wave at the webcam the cat will meow back.
Use the “when loudness >10” block,. Click the menu to change “loudness” to “video motion”. The script will start when you’re moving around.