50 free Sonar trivia questions with answers — technology quiz, new questions added Aug 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 50 questions with answers and explanations. Play the quiz
Q 01What does the acronym SONAR stand for?
Sound navigation and ranging
The study of underwater sound itself is called hydroacoustics.
Q 02Which kind of sonar emits pulses of sound and listens for the echoes?
Active
Passive sonar gives away nothing, which is why submarines rely on it most of the time.
Q 03Who is recorded as first using a tube in the water to detect ships by ear, in 1490?
Leonardo da Vinci
Underwater bells were later hung near lighthouses in the 19th century to warn ships of hazards.
Q 04Which 1912 disaster prompted the first patent for an underwater echo-ranging device?
The sinking of the Titanic
Richardson was a meteorologist; a German, Alexander Behm, patented an echo sounder the following year.
Q 05Which Canadian engineer detected an iceberg by echo ranging off Newfoundland in 1914?
Reginald Fessenden
His oscillator worked at about 500 Hz and could give range but not bearing.
Q 06Which French physicist worked with Constantin Chilowsky on detecting submarines in 1915?
Paul Langevin
Langevin drew on the piezoelectric effect discovered by Pierre Curie, using thin quartz crystals.
Q 07Which crystal did the first practical British echo-ranging apparatus use in 1917?
Quartz
Secrecy was so tight that the word quartz was replaced in paperwork by ASDivite.
Q 08What did the ASD in the British sonar name ASDIC actually stand for?
Anti-Submarine Division
In 1939 the Admiralty told the Oxford English Dictionary it meant Allied Submarine Detection Investigation Committee, a story still widely repeated though no such committee existed.
Q 09Which Harvard acoustics professor coined the term SONAR as an equivalent to RADAR?
Frederick Hunt
Hunt received the Medal for Merit from President Truman in 1947 for his wartime work.
Q 10What is the pulse of sound emitted by an echo-ranging sonar commonly called?
A ping
The round-trip time, scaled by the speed of sound and halved, gives the range.
Q 11Roughly how fast does sound travel in seawater?
About 1,500 metres per second
That is more than four times faster than sound moves in air.
Q 12Who showed on Lake Geneva in 1841 that sound is over four times faster in water than air?
Jean-Daniel Colladon
Colladon also campaigned to light Geneva with gas lamps, achieved on Christmas Day 1844.
Q 13What is the ocean temperature layer, 30 to 100 metres down, that bends sound?
The thermocline
American engineers discovered thermoclines and their effect on sound in the 1930s.
Q 21Which US Navy sonar used a large array of 432 individual transducers for decades?
AN/SQS-23
Its early transducers failed so often that the Navy switched to sealed, non-repairable modules.
Q 22Why does a towed array sonar trail its hydrophones far behind the vessel?
To escape the ship's own noise
It also covers the baffles, the blind spot directly astern of a hull-mounted sonar.
Q 23What is a hydrophone?
A microphone designed for underwater use
Most contain a piezoelectric transducer that produces a voltage when a sound wave squeezes it.
Q 14Which law describes how sound refracts as it crosses layers of different sound speed?
Snell's law
Higher pressure raises sound speed, so deep sound bends away from the high-speed region.
Q 15Which sailors' term describes sonar with the transmitter and receiver in the same place?
Monostatic
When they are separated, it is bistatic; most sonars use one array for both jobs.
Q 16Which anti-submarine weapon problem did the Hedgehog and Squid solve?
Losing contact when passing over the target
Depth charges had to be dropped over the stern, so the hunter went blind at the crucial moment.
Q 17Which Royal Navy officer developed the two-ship 'creeping attack' using ASDIC?
Frederic John Walker
One ship tracked the U-boat while a second, sonar off and at five knots, made the attack on its instructions.
Q 18Under what codename did the British develop the first sonobuoys in 1944?
High Tea
Britain had handed its ASDIC technology to the United States for free in September 1940.
Q 19What is a sonobuoy?
An expendable buoy dropped from aircraft or ships
A float with a radio transmitter stays on the surface while hydrophones sink to a chosen depth.
Q 20Which crystal made Rochelle salt obsolete in US transducers within nine wartime months?
Ammonium dihydrogen phosphate
Lead zirconate titanate (PZT) later became the standard piezoelectric material.
Q 24Which sound-emitting organ makes a fish visible to sonar?
Its swim bladder
Commercial fishing fleets now rely almost completely on sonar and sounders to find fish.
Q 25Which type sweeps fan-shaped pulses sideways to image the seafloor and find wrecks?
Side-scan
Marine archaeologists, shipwreck hunters and mine hunters all use it.
Q 26Which Tudor flagship did Harold Edgerton help locate in 1967 with Martin Klein's sonar?
Mary Rose
Klein's team had built the first successful towed commercial side-scan system between 1963 and 1966.
Q 27What does a multibeam echosounder produce from a single ping?
A swath of depth soundings
The US Navy's SASS system of the early 1960s pioneered swath mapping for its submarines.
Q 28Which method of measuring depth did echo sounding replace?
Lowering a weighted line
One of the first commercial units, the Fessenden Fathometer, went aboard the liner SS Berkshire in 1924.
Q 29Which German inventor was granted a patent for echo sounding in July 1913?
Alexander Behm
Like Richardson's British patent, it came in the wake of the Titanic sinking.
Q 30What is the SOFAR channel?
An ocean layer where sound speed is at its minimum
Sound trapped in it can travel enormous distances; Ewing and Worzel heard charges set off 900 nautical miles away in 1944.