Resonance is the driven or forced oscillation of a system at its natural frequency. Wind instruments use resonance in columns of air to amplify tones made by lips or vibrating reeds. In the flute family a jet of air sets the air in the tube vibrating, while other woodwinds use cane reeds. A sound spectrum is a graph of the different frequencies present in a sound, and bowed strings and winds have harmonic spectra. An instrument's timbre is set partly by the relative size of the different spectral components in its sound. The ear is most sensitive to frequencies around 3,500 hertz; the decibel is a logarithmic unit used to measure sound level. Listening for a long time to sounds at or above 85 decibels can damage hearing. Extremely loud noises can damage hearing too, and wearing earplugs in loud places helps protect it.
An octave is a ratio of 2:1 in frequency, and in equal temperament an octave has 12 equal semitones. By convention the note A4 is often set at 440 hertz. On a guitar, frets are metal strips along the fingerboard, each one a half-step apart. Opening a woodwind's holes one by one from the bottom end gives a chromatic scale. The belly, the top plate, is the most important part of the violin's body for pushing air. The Stradivari family of violin makers of Cremona lived from 1644 to 1737. In a double-blind test, 21 professional violinists played six violins, and only 8 of the 21 chose an old violin to take home; one of the new violins was chosen most often as the take-home instrument. George Beauchamp patented the electric guitar in 1936.
A piano's string vibrations pass through a bridge to a soundboard. Cristofori's hammers were covered in deer leather and hit the strings from below. A harpsichord's notes came when a plectrum made from a bird's quill or leather struck the string. Bartolomeo Cristofori, who worked for the Medici family in Florence, Italy, built the first piano in the early 1700s. Almost every modern piano has 88 keys. The earliest trumpets were signaling instruments used for military or religious purposes. Trumpets date back to 1500 BCE and earlier, and Tutankhamun's tomb held bronze and silver ones. Brass players make sound by buzzing their lips into a metal mouthpiece; the orchestra grew bit by bit from 1600 to 1900 but changed very little during the twentieth century. Every orchestra section has a principal who generally leads the group.
People who study the past say early music may have helped the first modern humans in Europe communicate and form tighter social bonds. In 1995 people in Slovenia found a juvenile cave bear's thigh bone with a line of small holes. Some say it is a Neanderthal flute, others that hyenas chewed it. Bone flutes between 7,000 and 9,000 years old were found at Jiahu, in the Yellow River Valley of China. Chinese teams dated the site with 20 radiocarbon dates from charcoal, plant ash and human bone. A joint Penn Museum and British Museum expedition to Ur in southern Iraq began in 1922. Woolley began a massive excavation there in 1926 and uncovered nearly 2,000 burials. The diggers found a great lyre with a gold and lapis lazuli bull's head, made about 2550 BCE.
In the Hornbostel-Sachs system an idiophone is an instrument whose own body vibrates, often by being struck. A membranophone is an instrument in which a membrane or thinly stretched material is vibrated. An aerophone is an instrument in which vibrating air produces the sound; a drum body acts as a resonant cavity: a frame drum with no box around it sounds loud but lacks depth, while a bigger enclosure gives a fuller, deeper sound. Robert Moog was fascinated by the theremin as a boy and built his first from plans in the magazine Wireless World. On a theremin the player's hand and an antenna form the two plates of a capacitor. As the hand nears the pitch antenna, the pitch gets higher.
Words to know
- resonance: strong matching shake
- spectrum: graph of frequencies
- octave: a 2:1 jump
- membranophone: drum-skin instrument
- aerophone: air instrument
- theremin: hands-free instrument
