1. Sound Sensation Lab SPARK Saturdays Hui Jun Tay & Ameya Kamat

2. Sound Sounds are vibrations that propagate in air Think ripples in a pond, waves on a beach

3. Sine Waves

4. Amplitude Measured in Decibels (dB) Loud noises have “bigger” vibrations ◦ Hitting a ruler hard vs hitting it softly

5. Microphone Loud sounds -> higher amplitude variation Louder sound hits the microphone -> higher voltage -> stronger signal Changes in pressure (due to vibration) correspond to changes in voltage

6. Speakers Basically work in reverse ◦ Based on voltage, generate vibrations

7. Sound of a Sine Wave “Pure” tone

8. Frequency Measured in Hertz (Hz) How fast it vibrates (cycles per second) ◦ Faster -> Higher Pitched ◦ Slower -> Lower Pitched

9. Fun Facts Humans: 20 – 20,000 Hz ◦ Younger people can hear higher frequencies! Dogs 20 – 45,000 Hz ‘Mosquito Frequency’ ringtone

10. Demo/Exporation Try different frequencies. Don’t hurt yourself!

11. Checkpoint #1 What we’ve learnt so far… ◦ Sound as a Sine Wave ◦ Amplitude ◦ Frequency

12. Actual Sound Do Voices and Music sound like that? ◦ No! Not one ‘pure’ sine wave, but multiple overlapping sine waves

13. Overlap +

14. Frequency Domain The different frequencies of a given sound

15. Different Instruments Audacity! ◦ Piano ◦ Trumpet ◦ Violin ◦ Bass

16. Checkpoint #2 What we’ve learnt so far… ◦ Sound as a Sine Wave ◦ Amplitude ◦ Frequency ◦ Multiple Sine Waves ◦ Frequency Domain

17. Filtering “Cut off” frequencies we do not want

18. Before and After FILTER!

19. Audacity Demo Filtering out an instrument Canon in D ◦ Violin, Cello, Guitar, Bass

20. Audacity Demo – Low Pass

22. Canon in D Four Instruments (Violin, Cello, Guitar, Bass) Try to get ◦ 1) only the bass ◦ 2) only the violin

23. Checkpoint #3 What we’ve learnt so far… ◦ Sound as a Sine Wave ◦ Amplitude ◦ Frequency ◦ Multiple Sine Waves ◦ Frequency Domain ◦ Filtering

24. Messing Around Record your voice on Audacity Apply filters, effects, anything you like Have fun!