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Beats

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Video Help(Malayalam) of the Beats applet

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This applet illustrates the superposition of two simple harmonic waves and the 'beats' phenomenon. The red wave is 'Freq. 1', the blue 'Freq. 2' and the green the superposition.

Keyboard Controls: 'Up' and 'Down' arrow keys increase and decrease 'Freq. 1'. 'Right' and 'Left' arrow keys do the same for 'Freq. 2'. The 'Space' key toggles the sound and the animation. Click inside the applet before you start using the keyboard controls.

Use the keyboard controls for changing the frequencies in steps of 1. You can change the frequencies while the sound and animation are on.

You are hearing the sound and the beats phenomenon ( the periodic waxing and waning in the sound ) in real time. The animation, however, is not in real time. Waves travel in air roughly at 300 m/s and that would be too fast to see. In the animation you see the waves in slow-motion. When you see the superposition ( the green wave ) becoming flat, remember that that corresponds to the 'waning' part of the sound you are hearing. When the beat frequency ( the difference between the two frequencies ) is small, you will have to wait for some time to see the change from the 'waning' part to the 'waxing' part of the green wave. If you choose large frequencies for both the waves and and a difference of about 200 or so you will be able to see the variation in the amplitude of the green wave in a much shorter length. Try this out with one wave at 3000 hz and the other at 3200 hz.

The Adobe Air version of this applet is here. Download and install. You need to have the latest Adobe Air installed, however.

You can download a Gtk+ 3 version of the applet for Linux, written in python, here. Please read the README file to install the dependencies. The file to be run is beatsapplet.py.

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