sine waves graphically

The sine wave is a "pure" tone, i.e. it is only a fundamental with no other overtones. All other sounds (musical or otherwise) are composites of sines (sinusoids according to Benade). Since doing the post on FirstSounds I became interested in how sines and other sounds looked so I started systematically doing some recordings with sine waves from a software synth (the Dreamstation).

The following images are from the editing software Cakewalk. Basically these pictures are telling us how the ear moves back and forth in response to sound waves. The interesting thing, of course, is how in compound sounds the ear is able to perceive more than one tone (or in other cases how it assembles one tone from many partials...more on that in a later post).

The first is of an A4 (the A above middle C).

Then a C5#.

And an E5 (now a major 10th above middle C).

Next are composites...First the major 3rd resulting from the A and C#.

Then the minor 3rd of C# and E.

Then the perfect 5th resulting from the A and E.

And finally the whole A major triad.


And one other interesting thing to note: these are time - amplitude graphs with the x-axis representing time and the y-axis amplitude (the middle horizontal line indicates the point where there is no sound, where the eardrum is in between being moved in and out). These images are small so it isn't evident in all of them, but by comparing the last one (the complete triad) with that of any of the single tones it is extremely easy to see that the triad is louder, exactly what one would expect (more sound = more volume).