- Blowing air into a whistle causes air to vibrate inside the whistle
- Vibrations are a source of sound
- So, the air vibrations inside the whistle are a source of sound

- The air vibrations inside the whistle are a source of sound
- Sound waves spread in all directions away from their source
- Therefore, the air vibration inside the whistle causes the sound waves to spread in all directions

Therefore, the air vibration inside the whistle causes the sound waves to spread in all directions
During a sporting event, a referee uses a whistle to alert the teams to start and stop playing. What causes the sound from the referee's whistle to travel in all directions?
- Blowing air into a whistle causes air to vibrate inside the whistle 
- Sound waves spread in all directions away from their source 
- Vibrations are a source of sound