Sonar Trivia
0Loading crowd target
0Loading crowd target
7correct to beat the crowd
49 free Sonar trivia questions with answers — technology quiz, new questions added Sep 2026.
This sonar trivia quiz covers the science and history of finding things with sound underwater, from Leonardo da Vinci's listening tube in 1490 to the towed arrays and multibeam sounders of today. The easy questions are ones a curious reader can work out: what the acronym stands for, the difference between active and passive sonar, what a ping is, how a fish finder spots a shoal and which animals were echolocating long before any navy. The harder end is for engineers, submariners and history readers: the disaster that spurred the first echo-ranging patent, the Canadian who detected an iceberg by sound in 1914, what ASDIC really stood for, the Harvard professor who coined SONAR, the ocean layer that bends sound and hides submarines, the codename of the first sonobuoys, the Cold War listening network that first tracked a Soviet nuclear submarine, and the whales most sensitive to naval sonar. Every answer was checked against encyclopaedia entries on sonar, its inventors and its systems before publishing, and the supporting sentence is stored with each question. If you enjoy this one, try our Submarines, Radar and Titanic quizzes next.
30 of 49 questions with answers and explanations. Play the quiz
Q 01What does the acronym SONAR stand for?
Sound navigation and ranging
Sound navigation and ranging was patterned on radar; Harvard's Frederick Hunt said he coined sonar around 1942 to make the Navy sound operator's job seem glamorous.
Q 02What turned out to cause the 'false bottom' that early sonar found in the deep ocean?
Swarms of small sea animals
Swarms of small sea animals, often fish, made the echoes; the layer rose toward the surface each evening and sank at dawn, which first suggested it was alive.
Q 03Who wrote around 1490 that a long tube dipped in water lets you hear ships far away?
Leonardo da Vinci
Leonardo da Vinci's instructions were to stop your own ship first, then put one end of a long tube in the water and hold the other to your ear.
Q 04Which maritime disaster spurred a wave of patents for detecting obstacles with underwater echoes?
The sinking of the Titanic
The sinking of the Titanic in 1912 drove the idea that a pulse's echo off an iceberg's hidden bulk could warn a ship, and the same pulse aimed down could measure depth.
Q 05Which Canadian engineer detected an iceberg by echo ranging off Newfoundland in 1914?
Reginald Fessenden
Reginald Fessenden's employer marketed his oscillator for underwater telegraphy and was reluctant to exploit its potential for finding icebergs and submarines.
Q 06Which French physicist worked with Constantin Chilowsky on detecting submarines in 1915?
Paul Langevin
Paul Langevin's first patent relied on an electrostatic 'singing condenser', a design that piezoelectric transducers later replaced.
Q 07Which crystal did the first practical British echo-ranging apparatus use in 1917?
Quartz
Quartz is piezoelectric: squeezing it makes a voltage and a voltage makes it flex, so it can turn electric signals into sound pulses and echoes back into signals.
Q 08What did the ASD in the British sonar name ASDIC actually stand for?
Anti-Submarine Division
Anti-Submarine Division is almost certainly the origin; the popular 'Detection Investigation Committee' story has left no trace in the Admiralty's archives.
Q 09What is the pulse of sound emitted by an echo-ranging sonar commonly called?
A ping
A ping gave its name to the network tool that times how long a computer takes to echo a message back, because it works like sonar.
Q 10Sound travels over four times faster in seawater than in which of these?
Air
Air carries sound at about 343 metres a second and seawater at about 1,500, so a sonar echo from a target 750 metres away returns in about a second.
Q 11How did two scientists on Lake Geneva time sound travelling through water in 1826?
Seeing a flash as a bell rang
Seeing a flash as a bell rang let Colladon and Sturm start the clock, because light crossed the lake almost at once while the bell's sound took several seconds.
Q 12Which ocean layer bends sonar beams so sharply that submarines can hide just beneath it?
The thermocline
The thermocline, where warm surface water gives way to cold deep water, bends sonar beams away, so ships tow their listening arrays below it to hear what hides there.
Q 13Which law describes how sound refracts as it crosses layers of different sound speed?
Snell's law
Q 21Why does a towed array sonar trail its hydrophones far behind the vessel?
To escape the ship's own noise
To escape the ship's own noise, the array trails far astern, which also lets it cover the baffles, the blind spot behind a hull-mounted sonar.
Q 22What is a hydrophone?
A microphone designed for underwater use
A microphone designed for underwater use let a Navy engineer at a secret Bermuda station, listening for Russian submarines, record whale songs that Roger Payne later released on an album.
Q 23Which part of a fish reflects sonar most strongly?
Its swim bladder
Snell's law is named for the Dutch astronomer Willebrord Snell, who found it in 1621 but never published it; sonar models use it to predict how beams bend.
Q 14Which airliner's wreckage on the deep ocean floor did sonar-equipped robot submarines finally find in 2011?
Air France Flight 447
Air France Flight 447's flight recorders, raised weeks later, showed the crew kept pulling the nose up even after the jet had stalled.
Q 15Which anti-submarine weapon problem did the Hedgehog and Squid solve?
Losing contact when passing over the target
Losing contact when passing over the target let U-boats dodge unseen, so the new weapons threw charges ahead while the escort's sonar still held the submarine.
Q 16Which Royal Navy officer developed the two-ship 'creeping attack' using ASDIC?
Frederic John Walker
Frederic John Walker's attacking ship crept in slowly with its ASDIC off, so the U-boat could not tell when the depth charges would fall.
Q 17Whose maps drawn from echo soundings revealed a rift valley running along the Mid-Atlantic Ridge?
Marie Tharp
Marie Tharp saw the rift in the 1950s, but her colleague Bruce Heezen dismissed it until earthquake records turned out to line up along the same valley.
Q 18What is a sonobuoy?
An expendable buoy dropped from aircraft or ships
An expendable buoy dropped from aircraft or ships keeps a radio float at the surface to relay what it hears below back to the patrolling aircraft.
Q 19What really makes the crack of a snapping shrimp, loud enough to drown out sonar?
A collapsing bubble
A collapsing bubble, formed as water jets from the closing claw, makes the noise; scientists had long believed it came from the claw halves hitting each other.
Q 20Whose long-lost plane did a sonar image seem to show in 2024, until a closer look found only rocks?
Amelia Earhart
Amelia Earhart's supposed plane only turned up when the sonar data was reviewed months into the trip, too late to turn back, so a second voyage was needed for a closer look.
Its swim bladder is full of gas, which reflects sound strongly, so sonar works best on fish such as herring and cod and poorly on sharks, which have none.
Q 24Which kind of sonar paints photo-like pictures of the seabed for wreck and mine hunters?
Side-scan
Side-scan sonar records how strongly the seabed echoes, so hard objects sticking up, like wrecks, stand out from soft mud and sand, which return weaker echoes.
Q 25Which Tudor warship's buried wreck did Harold Edgerton's sonar scans pick up in the late 1960s?
Mary Rose
Mary Rose's timbers were sprayed with chilled water and later polyethylene glycol after her 1982 raising, because drying out could have shrunk them by up to half.
Q 26Which novelist's 1984 debut follows a Soviet submarine whose silent drive leaves sonar operators struggling to hear it?
Tom Clancy
Tom Clancy, then a Maryland insurance agent, sold the book for $5,000, and it became a bestseller after President Reagan praised it.
Q 27Before echo sounders, sailors measured depth in fathoms, a unit first based on what?
The span of outstretched arms
The span of outstretched arms gave the fathom its name; a leadsman's cry of 'mark twain' meant two fathoms, the phrase Samuel Clemens made famous as his pen name.
Q 28What do sonar designers gain by choosing a lower-pitched sound?
It travels farther before fading
It travels farther before fading because seawater absorbs low notes only weakly; the trade-off is less detail and far larger equipment.
Q 29What is the SOFAR channel?
An ocean layer where sound speed is at its minimum
An ocean layer where sound speed is at its minimum traps sound so it travels great distances, and timing one blast's arrival at distant listening posts can pinpoint where it happened.
Q 30What was SOSUS?
A US system for tracking Soviet submarines
A US system for tracking Soviet submarines, SOSUS was so secret that even its name was classified, and its arrays were laid under the cover name Project Caesar.