Interesting Facts
The loudest natural sounds ever made on Earth are probably gigantic volcanic eruptions , such as the explosions of the island of Krakatoa.
Some of the loudest sounds produced by our own invention are the noise of space rockets blasting from the launch pad. The biggest were the Saturn V rockets that launched the USA's Apollo moon missions of 1968-72. They had their greatest success when Apollo 11 landed on the Moon - an airless and therefore completely silent place - on 20 July 1969. Once a space rocket had taken off and entered the vaccum of space, it became totally silent.
Thin-glass goblets can vibrate when hit by sound waves. This is due to resonance. Some singers listen to the note produced when a glass, so that their voice vibrates the glass so much that it shatters.
The same may happen to glass windows when vibrated by sound waves. In one church, the loud clang of a large ball shattered the stained-glass window above the altar.
A few musical instruments are named after their inventors. From the 1840s came the saxophone, after the American marching - music composer John Philip Sousa. Much more modern is the moog electronic synthesizer (pronounced 'mowg'). The first version was made in 1964 by American electronics expert Robert Moog.
Somes musical instruments have developed from devices used originally to send sound signals for communication. Some of the best examples are drums and horns.
One musical piece has no sound at all. It is called 4 minutes 33 seconds. It was ' written ' by the American composer John Cage in 1954. A pianist sits at the piano and plays nothing for exactly 4 minutes and 33 seconds.
In theAlps mountains of Europe the long wooden trumpet called alphorn was used by herdsmen to call each other . Also called the alpenhorn and alpine horn, its loud, deep trumpeting sound echoed across the valleys and summoned people to church - or to war. Similar instruments were used in upland regions of Germany, Scaninavia and Eastern Europe.
Middle C , with a frequency of 256 Hertz,is near the top of the singing range of a typical adult male voice. It is also near the lower end of the singing range of an adult female voice.
The noise from juggernaut trucks can shake and damage may come from sound waves throught the air or from very low-frequency vibrations passing through the ground.
The BA-Aerospatiale Concorde is the only passenger plane to fly faster than sound, at 2100 kph.
No other animals can copy the sounds of our own speech and understand its meaning - not even our nearest relatives, the chimpanzees. Although to do this, chimps can learn to understand messages and 'speak' in a silent way, by sign language. They make signs with their hands and put together simple sentences such as " Give me food! "
Emile Berliner's first flat - disc recordswere made of hard rubber. This was followed by shellac, aresin-type substance originally obtained from certain insects. Eventually plastic were tried, including vinyl.
In fibre-optic cables a voice on the telephone becomes coded as flashes of laser light. These pulse millions of times per second. Light travels more efficiently in long cables than electricity.
In the1880s Alexander Graham Bell worked on a fibre-optic device called the photophone, but it never became practical.
In the deep ocean . the sperm whale uses sound to stun or kill its prey. Its sends out giant grunts, immensely powerful bursts of sound that can disable nearby fish, squid and other victims.
In the middle of the night , an eerie tap-tap-tap in an old building was thought to be a ghost or spirit , came to take away the living , of returned with the souls of the dead. In fact, it is the dead-watch beetle banging its jaws and head on the wood. The tapping sound was its call for a mating partner. The beetle's grubs tunnel into oak trees and old oak beams in houses.
Acoustics plays a large part in the design of modern concert halls, theatres and similar buildings. The travels of a sound wave can be shown on acomputer screen, for different frequencies and for different materials covering them. This is why many such buildings have strange shapes on the walls and ceiling, such as discs , panels and saucers , to absorb or reflect the sounds.
Huge cathedrals, with their hard walls and floors of stone, glass and wood, are amazing places for acoustics. Almost any sound seems loud and long, a sit echoes and reverberates through the surfaces. This is why church singing sounds so special.
In the recording studio any stray sound is a nuisance. So the walls, ceilings and floors are covered with sound-absorbing substances, such as wavy-surfaced tiles and thick carpets. There is a continuing search for 'acoustically dead' materials that absorb all sounds.