1. + Audacity tutorials on how to show them off
Acoustic Beats
+ Audacity tutorials on how to show them off

2. 1. What is an acoustic beat?
2. How to get an acoustic beat
3. Uses of acoustic beats
4. Chords
5. Temperament

3. Overview
An acoustic beat is an effect caused when two near identical frequencies are played simultaneously.
When two coherent sound sources come from the same direction, their waveforms superimpose onto each other. If two waves are coming towards you and the frequencies are differing by a slight amount, then their waveforms “slip out” of phase, and cause irregularity over time in how the minima and maxima of both waveforms add together.
This causes a pulsating sound, as the overall amplitude of the two waves oscillates over time (At a frequency of half the difference of the two waves)
This effect is physical, not neurological. Therefore If the two waves never have the chance to meet, no beats occur. This is known as a binaural beat, and is famous for sounding relaxing to some people. There are 3 hour long videos of this tone on YouTube.

4. In Audacity
Audacity can be downloaded here at sourceforge for free. The install process is simple and doesn't try to install any toolbars. Some of the other links on the first page of google are dodgy so watch out!

5. Create a new project in audacity
Add a new audio track
In this track, generate a tone.

6. A box will open and let you choose the characteristics of the wave
A box will open and let you choose the characteristics of the wave. Waveform: A sine wave is the purest waveform. It’s the best choice to show the effect clearly. Frequency: 440 (Musically the note of A) is the standard frequency. instruments are tuned to. It is a good frequency to use out of tradition, and also as it is audible on speakers but also not too high pitched to be an annoying demonstration. Amplitude: The default setting for this is 0.8. The effect will still be noticeable at that level, but the summation of two waveforms with that amplitude will cause clipping, and the resulting distortion distracts away from the desired effect. 0.4 dosen’t cause any clipping, so choose that.

7. Now create another waveform with all the same values, but with a small difference in frequency. For example, 445Hz
*These values show off the effect best on standard speakers, but the effect will work at any value chosen, as long as the discrepancy of the frequencies of the two waveforms is sufficiently small. The waveforms and amplitude don’t actually have to be the same to create a pulsating effect. Once you have finished doing this using sine waves, try the same with a sawtooth wave, and the pulsation is more triangular than sinusoidal.*
Now the two waveforms are ready, press play, and you should notice the pulsating effect quite clearly.