Vibrational Modes of the (1,1) Mode

The second mode of vibration of a circular membrane is the (1,1) mode. This is the most imporant vibrational mode in terms of the musical quality of the drum. The (1,1) mode vibrates at a freqeuncy 1.593 times the frequency of the (0,1) mode, and the nodal point runs the diameter of the drum.

In this mode, the membrane is acting as a dipole vibrational sound source. As a dipole, the air that is being pushed out by the drum can simply move over and fill the space on the other side. Forcing the air back and forth takes much less energy than the (0,1) mode and, therefore, the vibrations decay much more slowly than with the (0,1) mode. This longer decay means the drum will resonate and, therefore, create a sound that continues for up to several seconds, giving the drum a musical quality.

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