This is an animation of a traveling wave.  
	f(x,t) = sin( kx + wt )
For simplicity, k and w are set to 1.

To see the animation, select the bracket with an arrow in the right side of the graphics by using the pointer and the mouse button, then select "Animate Selected Graphics..." in the Graph menu.  
You can control the animation with buttons will appear in the bottom of this window.

Do[
	Plot[Sin[x-t],{x,-2Pi,2Pi}],
	{t,0,2Pi,Pi/20}
]

This is an example of the UNARI (Japanese).
		f(t) = sin(w1t) + sin(w2t)
w1 and w2 are set to 0.95 and 1.05, respectively.

Plot[Sin[0.95t]+Sin[1.05t],{t,-20Pi,20Pi}]

This is an animation of the UNARI.  The frequency difference was changed from 0% to 10% smoothly.

Do[
	Plot[
		Sin[(1-0.05 Sin[b])t]+Sin[(1+0.05 Sin[b])t],
		{t,-20Pi,20Pi}
	],
	{b,0,Pi,Pi/20}
]