Sound Sensation LabSPARK Saturdays
Hui Jun Tay & Ameya Kamat
SoundSounds are vibrations that propagate in airThink ripples in a pond, waves on a beach
Sine Waves
AmplitudeMeasured in Decibels (dB)Loud noises have “bigger” vibrations
◦Hitting a ruler hard vs hitting it softly
MicrophoneLoud sounds -> higher amplitude
variation
Louder sound hits the microphone -> higher voltage -> stronger signal
Changes in pressure (due to vibration) correspond to changes in voltage
SpeakersBasically work in reverse
◦Based on voltage, generate vibrations
Sound of a Sine Wave“Pure” tone
FrequencyMeasured in Hertz (Hz)How fast it vibrates (cycles per second)
◦Faster -> Higher Pitched◦Slower -> Lower Pitched
Fun Facts
Humans: 20 – 20,000 Hz◦Younger people can hear higher
frequencies!Dogs 20 – 45,000 Hz
‘Mosquito Frequency’ ringtone
Demo/ExporationTry different frequencies.Don’t hurt yourself!
Checkpoint #1
What we’ve learnt so far…◦Sound as a Sine Wave◦Amplitude◦Frequency
Actual SoundDo Voices and Music sound like that?
◦No!
Not one ‘pure’ sine wave, but multiple overlapping sine waves
Overlap
+
Frequency DomainThe different frequencies of a given sound
Different Instruments
Audacity!◦Piano◦Trumpet◦Violin◦Bass
Checkpoint #2
What we’ve learnt so far…◦Sound as a Sine Wave◦Amplitude◦Frequency◦Multiple Sine Waves◦Frequency Domain
Filtering
“Cut off” frequencies we do not want
Before and After
FILTER!
Audacity Demo
Filtering out an instrument
Canon in D◦Violin, Cello, Guitar, Bass
Audacity Demo – Low Pass
Audacity Demo – Low Pass
Canon in D
Four Instruments (Violin, Cello, Guitar, Bass)
Try to get ◦1) only the bass◦2) only the violin
Checkpoint #3
What we’ve learnt so far…◦Sound as a Sine Wave◦Amplitude◦Frequency◦Multiple Sine Waves◦Frequency Domain◦Filtering
Messing Around
Record your voice on AudacityApply filters, effects, anything you
likeHave fun!