﻿ Computer Bases Physics
: Lissajous Curve Demonstration / Your Voice /
YOUR VOICE

In this computer based physics, you can see the waveform and the Fourier spectrum produced by your voice and by a 400, 500, and 600 Hz tone as well as a combination of them.

TO BEGIN:

Left click the mouse, then left click “MUSEUM”. Check that the “Time Range” is approximately 20ms, and then adjust the “Frequency Range” by entering the values from 20 Hz to 2000 Hz.

DO:     Check that the 400, 500, and 600 switches are off and the “your voice” switch is on. Use the microphone and sing various tones using the same vowel at different pitches. Try a loud “aaah” for example.

SEE:   On the screen you will see the waveform produced by your voice. You will also see another shape the Fourirer spectrum of your voice. Notice the difference in both of these the display produced by high and low pitch tones.

DO:     Sing various tones using different vowels, at about the same pitch.

SEE:   Look at the shape of the waveform and Fourier spectrum of your different vowels. See how an ..AAA.. differs from an ..UUU.. for example.

WHAT IS THE FOURIER SPECTRUM ANYHOW?

MAKE A FEW TESTS

DO:     Turn the 400 switch on. Check that the 500 and 600 switches are off and that “your voice” switch is also off.

HEAR: Use the headphones to hear the 400 Hz tone, and play with the amplitude knob to make the tone louder and softer.

SEE:   The waveform produced by a 400Hz tone: is a smooth curve, it’s a sine wave. See also that the Fourier spectrum shows a single peak at 400Hz, The height of the peak changes if you change the loudness of the tone

DO:     Turn the 400 Hz   switch off and turn the 600 Hz switch on.

SEE:   Again see the waveform produced by a 600 Hz tone: it is a smooth curve, it’s a sine wave. See also that the Fourier spectrum shows a simple peak at 600Hz.

NOW TRY SOMETHING HARDER

DO: Turn the 400, 500 and 600 switches on. Check that “your voice” switch is off.

HEAR: Use the headphones to hear the tone, play with the three amplitude knobs and hear how the quality of the tone changes.

SEE:   The waveform produced by the sum of the three tones is a smooth curve, but it not a sine wave. The sum of three sine curves and its shape depends on the amplitudes you have chosen for the different components. See also that the Fourier spectrum shows three peaks, corresponding to the frequencies.

THE POINT OF ALL THIS

The complicated waveform produced by your voice is actually the sum of many sine waves, each one corresponding to a different resonance of your oral cavity.