What is Sound?   Before going into the science of how a clarinet works, lets have a quick discussion of what sound is. When many people describe sound, they often describe it as a wave. But what exactly does that mean? Normally, when someone imagines a wave, they imagine ocean waves or earthquakes. How could sound possibly possess these same qualities? As it turns out, sound is a sort of compressional wave, much different from how many other waves function. While ocean waves represent changes in the oceans height at any point, compressional wave can be represented by a change in pressure. http://pondscienceinstitute.on-rev.com/svpwiki/tiki-index.php?page=Figure+9.11+-+Compression+Wave+with+expanded+and+contracted+Orbits   As in the picture above, particles move and bump into other particles. This creates regions of both high and low pressure. These changes in pressure are picked up by the ear and interpreted as sound. Depending on how many times per second the high pressure regions reach the ear, the pitch will be interpreted differently by the ear. By increasing the frequency, you increase the pitch.