Sinusoidal wave going trough entire human audio spectrum, starting at 20Hz and ending at 20kHz. Note that the frequency increases exponentially, the idea was to increase the frequency by constant fraction of currently played frequency rather than by a constant value (which would result in clearly noticeable fast change at lower frequencies and nearly no change at higher frequencies). Enjoy. Note:
![20Hz to 20kHz (Human Audio Spectrum)](https://cdn-ak-scissors.b.st-hatena.com/image/square/ccd0eac61925361fefdbc32d7e349cbf067c1af4/height=288;version=1;width=512/https%3A%2F%2Fi.ytimg.com%2Fvi%2FqNf9nzvnd1k%2Fhqdefault.jpg)