Organ pipes info

Waves in organ pipes are similar to waves on strings - both are mechanical, requiring a medium.

The string wave is fixed (nodes) at both ends.  The organ pipe waves is open at both ends - it has anti-nodes at both ends.

http://www.physics.smu.edu/~olness/www/05fall1320/applet/pipe-waves.html

Also, the string wave is TRANSVERSE.  The wave energy travels up and down - perpendicular to the medium (string).

The sound wave is LONGITUDINAL, also known as compressional.  The wave energy (manifested in the motion of the air molecules) jiggles back and forth - parallel to the medium.

However, the air molecules motion can be modeled with a sine wave.  Even though the molecules themselves don't move up and down like a sine wave, their relative position (and therefore the relative density inside the tube) behaves in a sine-like fashion.  So, we can model the motion with a sine graph and treat it just like a string, even though it's very different.  The math, as it turns out, is the same for both.