Unlike conventional musical instruments where the sound energy vibration is limited to a one-dimensional path, sound vibrations in a drumhead can travel anywhere within a round two-dimensional space. The distance straight across the drumhead defines one wavelength series. A round zero movement node is established by the fixed rim-edge drumhead attachment. As we can see in the far left hand animation below viewing a drumhead vibrating at the fundamental resonance, from the side looks like one half of a sine wave, with alternating up and down motion.
About Drums