Strings and pipes in music String instruments

Stretched strings may be made to vibrate at characteristic frequencies. The surface area of a vibrating string is too small to compress the surrounding air effectively and string instruments use sound boards to amplify the vibrations.

Instruments which have strings mounted paralled to the soundboard and a body which resonates are generally known as lutes. The earliest lutes were long-necked and made from materials such as hide and turtle. There is evidence for the existence of lutes in Egypt and Mesopotamia (modern Iran) as early as about 2,500 BC. The European lute was modelled on the classical Arab instrument, Aloud (meaning a wooden stick), a short-necked instrument with a body of lightweight wood. The Europeans modified the Arabic design by introducing frets (metal strips embedded in the neck of the instrument).

The earliest surviving classical (six-string) guitars were made in Naples towards the end of the eighteenth century. The body shape of the modern guitar was largely standardized by the Spanish guitarist and guitar maker Antonino de Torres (1817-1892) in Seville in the mid to late nineteenth century.

The acoustic guitar does not use any external means of amplification. Vibrations produced by plucking the strings are transmitted to the body of the guitar, which resonates at the frequency of the vibrating string. Sound generated in the chamber is projected into the air through the sound hole. Strings are stretched from the bridge to the top of the neck. The vibrating lengths of a string Acoustic guitar. Courtesy of Massimo Giuliani.

may be shortened by pressing it against the frets to produce sounds of different pitch.

The modern form of the violin dates from the mid sixteenth century. These early violins were made in northern Italy, By 1600, the centre of violin making was Cremona, where Nicolo Amamti (1596-1684) and Antonio Stradivari (1644-1737) worked. It is remarkable that violins made centuries ago are now cherished for their beautiful sound. Violinmakers such as Stradivari, knowing only practical physics and acoutics, were able to produce instruments so desirable that they are highly prized. The Stradivarius violin known as 'The Hammer' sold at public auction in 2006 for more the $3.5M.

Wind instruments

A column of air, like a stretched string, can be made to vibrate at a series of frequencies whose values depend on the length of the column and on whether it is open at one or both ends (see 'standing waves').

Woodwind instruments such as the clarinet and the flute have a long, thin column of air with a series of tone holes. The pitch is changed by opening or closing the holes. The lowest (fundamental) note is produced when all the holes are closed.

The clarinet is a reed instrument. Standing waves are excited by vibrations of the reed. The mouthpiece is closed during play and even harmonics are strongly suppressed, as would be expected for a column of air closed at one end. The flute, on the other hand, is open at both ends. Standing waves are excited when air is blown across the open mouthpiece. Adjacent odd and even harmonics are fairly equally represented.

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