Harmonic Balance
From SwordWiki
The "Harmonic Balance" of a sword is the way vibration and oscillation travels within the sword. Specifically, the term is often used in reference to how shock and vibration is transmitted to your hand when the blade strikes an object.
The sword, like any elongated physical object, will have "harmonic nodes", which are points along its length that will pivot rather than move when the sword is oscillating. Swords will have two such harmonic nodes, with the one at the furthest end of the sword being referred to as the Center of Percussion. This "CoP" is often viewed as the blade's "sweet spot", where a strike against a target will result in the least vibration being generated within the sword.
Many factors contribute to the location of the harmonic nodes, including length, mass, distribution of mass, overall and relative hardness/flex of the materials, and so on.
The resulting Harmonic Balance will influence the overall feel of the sword, since ideally the Center of Percussion should be at a natural position on the blade for striking targets, and the nearer Harmonic Node should be near the front end of the grip.
Determining the location of the harmonic nodes is relatively easy. To find the Center of Percussion, there are two options. First is to hold the blade by the grip, point upwards, and strike the flat side of the blade with the heel of your other hand to induce a vibration. The second, and perhaps preferable method, is to hold the sword by the pommel, point down, and strike the side of the grip or guard with the heel of your hand to induce vibration. In either case, the point along the blade that appears to be stationary is the CoP.
Locating the secondary Harmonic Node is similar. Grip the sword with your index finger and thumb on the grip, just behind the guard, facing the point down. Strike the pommel with the heel of your hand, and feel the vibration in your fingertips that are gripping the sword. Repeat the process moving your grip location up and down the guard, and find the location that has the least sensation of vibration.
See also: Center of Percussion
