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!