Wind chimes are a type of percussion instrument constructed from suspended tubes, rods, bells, or other objects that are often made of metal or wood. The tubes or rods are suspended along with some type of weight or surface which the tubes or rods can strike when they or another windcatcher surface are blown by the wind outside.
They are usually hung outside of a building or residence as a visual and aural garden ornament. Since the percussion instruments are struck according to the random effects of the wind blowing the chimes, wind chimes have been considered an example of aleatoric music. The tubes or rods may sound either indistinct pitches, or fairly distinct pitches. Wind chimes that sound fairly distinct pitches can, through the chance movement of air, create simple songs or .
glass wind bells known as fūrin (風鈴) have been produced since the Edo period, and those at Mizusawa Station are one of the 100 Soundscapes of Japan. Wind chimes are thought to be good luck in parts of Asia and are used in Feng Shui.
Wind chimes started to become modernized around 1100 C.E. after the Chinese began to use metal casting to create bells. A bell without a clapper, called a yong-zhong, was crafted by skilled metal artisans and primarily used in religious ceremonies. Afterwards, the Chinese created the feng-ling (風鈴]]), which is similar to today's modern wind bell. Feng-lings were hung from shrines and pagodas to ward off evil spirits and attract benevolent ones. Today, wind chimes are common in the East and used to maximize the flow of chi, or life's energy.
Most chimes employ pentatonic scale or as the basis for the pitches of their individual chimes as opposed to the traditional western heptatonic scale. This is largely due to the fact that these scales inherently contain fewer dissonant intervals, and therefore sound more pleasant to the average listener when notes are struck at random.
In instruments such as , the pitch is determined primarily by the length of the air column, because it is the resonance of the air column that generates the sound. The pipe material helps determine the "timbre" or "voice" of the pipe, but the air column determines the pitch. In a wind chime, the vibrations of the pipe itself radiate the sound after being struck, so the air column has little to do with the pitch being produced.
Sound can be produced when the tubes or rods come in contact with a suspended central clapper in the form of a ball or horizontal disk, or with each other.
Wind chimes may be used to observe changes in wind direction, depending on where they are hung when they commence to sound.
The tone depends on factors such as the material used, the exact alloy, heat treatment, and whether a solid cylinder or a tube is used. If a tube is used, the wall thickness also affects the tone. Tone may also depend on the hanging method. The tone quality also depends on the material of the object that is used to hit the chimes.
With clay wind chimes, the higher the final firing temperature, the brighter and more ringing the resulting tone. Earthenware clay fired at lower temperatures produces a duller sound than stoneware clay fired at higher temperatures. Stoneware wind chimes are also more durable and able to resist stronger winds without suffering chipping or damage.
where L is the length of the tube, E is the Young's modulus for the tube material, I is the second moment of area of the tube, and μ is the mass per unit length of the tube. Young's modulus E is a constant for a given material. If the inner radius of the tube is ri and the outer radius is ro, then the second moment of area for an axis perpendicular to the axis of the tube is:
The mass per unit length is:
where ρ is the density of the tube material. The frequency is then
where W=ro-ri is the wall thickness and D is the average diameter D=ro+ri. For sufficiently thin-walled tubes the W2 term may be neglected, and for a given material, the main frequency is inversely proportional to L2 and proportional to the diameter D.
For the main mode of vibration, there will be two nodes on the tube, where the tube is motionless during the vibration. These nodes will be located at a distance of 22.416% of the length of the tube from each end of the tube. If the tube is simply supported (not clamped) at one or both of these nodes, the tube will vibrate as if these supports did not exist. A wind chime will give the clearest and loudest tone when it is hung using one of these node points as the attachment point. These attachment points are also the same as used by other similar instruments such as the xylophone and glockenspiel.
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