50 Fun Facts About Sound

Which nursery rhyme did Thomas Edison recite in 1877 to test his newly built phonograph?

Mary Had a Little Lamb was scratched into a sheet of tinfoil wrapped round a cylinder, then played back. That first recording was never preserved.

The sharp crack of a bullwhip is produced when its tip travels fast enough to create what?

A sonic boom in miniature: a loop racing down the whip speeds up until the tip passes the speed of sound, more than 30 times faster than the handle moved.

A space explosion would be silent to a nearby astronaut because sound cannot travel through what?

A vacuum has no particles to pass the vibrations along. Robert Boyle is credited with discovering the part air plays in carrying sound.

Which volcano's 1883 eruption made the loudest sound in recorded history, heard 4,800 kilometres away?

Krakatoa's blast was heard on Rodrigues, an island near Mauritius, where people took it for cannon fire from a ship.

The pop heard when people crack their knuckles comes from which of these inside the finger?

Bubbles in joint fluid form as the knuckle is pulled apart and dissolved gas comes out of solution. It takes about 20 minutes before the same knuckle can crack again.

The smallest bone in the human body sits in the middle ear and is named after which riding item?

Stirrup is what its Latin name, stapes, means. It is the last of three tiny bones that carry vibrations across the middle ear.

Which gas makes a voice squeaky because sound travels nearly three times faster through it than through air?

Helium does not change how fast the vocal cords vibrate. Faster sound in the throat and mouth boosts the high parts of the voice, which changes its tone.

A person's recorded voice sounds higher than expected because it lacks vibrations carried through what?

The skull carries low notes better than air does, so the voice you hear while speaking is deeper and fuller than the one everybody else hears.

Which land animals keep in touch across several kilometres using rumbles too low for people to hear?

Elephants make these calls below about 20 vibrations a second, under the floor of human hearing, and they may carry as far as 10 kilometres.

Which stock sound effect, recorded for a 1951 film, turns up in Star Wars and Indiana Jones movies?

The Wilhelm scream began as a take labelled "Man getting bit by an alligator, and he screams". Its name comes from Private Wilhelm, a character in a 1953 western.

Which familiar sound is a shock wave from air heated in an instant to nearly 30,000 degrees Celsius?

Thunder trails its flash because light arrives almost at once while sound needs about three seconds per kilometre, so the gap tells you how far away the strike was.

Which skill lets bats and dolphins find prey by listening for their own calls bouncing back?

Echolocation was only given its name in the 1940s by zoologist Donald Griffin, who helped show that bats steer by calls too high for people to hear.

The drop in the note of an ambulance siren as the vehicle speeds past is named after which physicist?

Christian Doppler described the effect in 1842. Three years later Buys Ballot tested it with musicians playing one steady note on a moving train.

The decibel, the unit used to measure loudness, is named in honour of which inventor?

Alexander Graham Bell, the telephone pioneer, gave his name to the bel, and a decibel is a tenth of one. Every rise of 10 decibels means ten times the sound power.

Which quality of a note, high or low, depends on how many times each second the sound wave vibrates?

Pitch climbs as the vibrations get faster. The A above middle C that musicians use as a standard vibrates 440 times each second.

Which kind of sound, too high for human ears, do doctors use to make images of unborn babies?

Ultrasound lies above roughly 20,000 vibrations a second. A scanner sends pulses into the body and builds a moving picture from the reflections that return.

Which listening device did French doctor René Laennec invent in 1816 as a plain wooden cylinder?

Stethoscope in hand, Laennec no longer had to press his ear to a woman's chest to hear her heart, which had made him uncomfortable.

Male crickets make their chirping song by rubbing together which parts of the body?

Wings, not legs: male crickets scrape specially textured parts of the two front ones together. The song is meant to attract females.

The 'ocean' heard inside a seashell held to the ear is really what, made louder by the hollow shell?

Surrounding sounds are caught and boosted by the hollow shell. An empty cup, or a hand cupped over the ear, does the same job.

Which term describes words such as 'buzz' and 'cuckoo' that imitate the sounds they name?

Onomatopoeia comes from Greek words meaning 'name-making'. Languages hear things differently: an English frog says ribbit, while an ancient Greek one went brekekekex.

Which branch of science, named from a Greek verb meaning 'to hear', is the study of sound?

Acoustics covers every kind of mechanical wave in gases, liquids and solids, including vibrations far too high or too low for anyone to hear.

Which throat organ enlarges in boys at puberty, deepening the voice and pushing out the Adam's apple?

Larynx is the proper name for the voice box. As it grows, the vocal cords inside become longer and thicker, which is what lowers the voice.

Which snail-shaped part of the inner ear turns sound vibrations into nerve signals sent to the brain?

Cochlea comes from the Latin for snail shell. In humans the spiral coils two and three-quarter times around its core.

Which technology, developed in World War I to find submarines, locates objects with pulses of sound?

Sonar is short for sound navigation and ranging. Interest in finding objects underwater by sound seems to have been spurred by the Titanic disaster of 1912.

Which American test pilot first flew faster than sound, in the rocket-powered Bell X-1 in 1947?

Chuck Yeager made the flight with two ribs broken in a riding fall two nights earlier. His plane was named Glamorous Glennis after his wife.

Which airliner, retired in 2003, carried passengers across the Atlantic at twice the speed of sound?

Concorde more than halved journey times, but the shock wave it dragged across the ground kept its fastest flying to routes over the ocean.

Which effect lets a singer shatter a wine glass by holding a note at the glass's natural frequency?

Resonance builds when each push arrives in step with the last, as with well-timed shoves on a playground swing, until the glass flexes too far and breaks.

Which Australian bird can mimic chainsaws, car alarms and camera shutters as well as other birds?

Lyrebird song mixes the bird's own notes with sounds heard nearby. The birds copy the calls of whole flocks, and of koalas and dingoes, with great fidelity.

Which animal makes the loudest sound of any creature, a click used to hunt squid in the deep sea?

Sperm whale clicks are made by the huge organ complex in the animal's head, which focuses them into a narrow beam for finding prey in the dark.

Francis Galton's 1876 whistle, too high for human ears, is used to train which animals?

Dogs hear notes well above the human limit, as do cats. Galton built the whistle to test the hearing range of different animals.

Turning up a speaker's volume raises which property of a sound wave but leaves its frequency alone?

Amplitude, for sound, means the size of the swings in air pressure. How loud that feels also depends on the note, because ears are keener at some frequencies than others.

Which unit of frequency honours the German physicist who first proved that electromagnetic waves exist?

Hertz officially replaced the older name "cycles per second" in 1960. One of them means a single vibration each second.

Sound moves at nearly 6,000 metres per second, some 17 times its speed in air, through which material?

Steel carries sound fast because it is stiff: the harder a material resists being squeezed, the quicker it hands a vibration on. Water manages only about a quarter of that speed.

The speed of sound in air depends mainly on which factor, making it slower at a jet's cruising height?

Temperature decides it: the thinner air and the lower pressure high up cancel each other out, leaving only the cold to slow sound down.

Doubling the frequency of a musical note raises it by which interval, the gap from one C to the next?

An octave joins notes that sound so alike they share a letter name. The C above middle C vibrates about 523 times a second, twice as fast as middle C.

Which woodwind instrument plays the A that a symphony orchestra tunes to before a concert begins?

Oboe players give the note because the instrument holds its tuning securely and its penetrating tone carries across the whole orchestra.

Which quality of sound lets a listener tell a guitar from a piano playing the same note equally loudly?

Timbre comes from the mix of fainter, higher vibrations layered over the main note. Every instrument, and every human voice, has its own recipe.

What are everyday film sounds such as footsteps and squeaky doors, recorded after shooting, called?

Foley takes its name from Jack Foley, a sound-effects artist. Performers act out each footstep and door slam in time with the picture.

Which name is given to a steady hiss with equal energy at every frequency, often sold as a sleep aid?

White noise is named by analogy with white light, a blend of every colour. Machines that play it are also used to mask ringing in the ears.

Sound in air is which type of wave, with particles moving back and forth along its direction of travel?

Longitudinal waves squeeze and stretch the air along their path. Only in solids can sound also travel as a sideways shake.

Half of every sound wave is a compression; what is the other half, where air thins out, called?

Rarefaction is where the air's particles are spread thinnest. A sound wave is a chain of these gaps alternating with squeezed regions, one pair for each vibration.

Which word describes sound lingering in a hall after the source stops, as reflections build and fade?

Reverberation fades as the sound is soaked up by whatever is in the room, which is why a hall full of people and furniture sounds drier than an empty one.

Which wave behaviour lets a marching band's bass drum be heard round a corner before its flutes?

Diffraction, the bending of waves around obstacles, is stronger for longer waves. Deep notes have the longest waves, so they turn corners that high notes cannot.

Which sea creature snaps an oversized claw shut so hard that the shock wave can stun nearby fish?

Pistol shrimp claws can be longer than half the animal's body. The snap is violent enough to give off a brief flash of light along with the bang.

Which ambient music pioneer composed the six-second start-up sound of Windows 95?

Brian Eno later admitted that he wrote the Windows chime on a Macintosh. "I've never used a PC in my life; I don't like them," he said.

Which company's audio trademark is the Deep Note, a swelling chord that debuted with Return of the Jedi?

THX had the sound built on a computer by James Moorer of Lucasfilm. It starts as a narrow cluster of tones that slides apart into a huge, wide chord.

The Bloop, a mysterious and very loud ocean sound recorded in 1997, turned out to come from what?

An icequake was the source: an iceberg cracking and breaking away from an Antarctic glacier. The researchers who recorded it had been listening for volcanoes.

What is the medical name, taken from ancient Greek, for the rumbling sound of the stomach?

Borborygmus is made as waves of muscle contraction squeeze gas and fluid along the gut, in the intestines as well as the stomach, and an empty gut makes it louder.

Which physicist made sound visible by drawing a bow across metal plates sprinkled with sand?

Ernst Chladni showed the patterns in Paris to an audience that included Napoleon, who put up a prize for the best mathematical explanation of them.

Which British physicist wrote The Theory of Sound and later won a Nobel Prize for discovering argon?

Lord Rayleigh also explained why the sky is blue: tiny particles in the air scatter light, and the effect now carries his name.