question: Why does cracking your knuckles under water seem to amplify the sound it makes?
comment: When you make a sound, you compress the molecules around into waves. These waves hit your ear, and you perceive it as sound. Air is a lot less dense than water, so when you create these waves, a lot of the energy is soaked up by the molecules hitting a neighbouring molecule, kind of like kicking a football into another football. In water, because the molecules are so close together, very little energy is released when the molecules bang into eachother as the wave transfers through the liquid. You can demonstrate this high transfer of power with a Newton’s Cradle. So to conclude, the water density is higher, meaning the sound and distance a wave can travel is much higher than in air
passages: The influence of sonic waves traveling through liquids was first reported by Robert Williams Wood (1868–1955) and Alfred Lee Loomis (1887–1975) in 1927. The experiment was about the frequency of the energy that it took for sonic waves to "penetrate" the barrier of water. He came to the conclusion that sound does travel faster in water, but because of the water's density compared to our earth's atmosphere it was incredibly hard to get the sonic waves into the water. After lots of research they decided that the best way to disperse sound into the water was to make loud noises into the water by creating bubbles that were made at the same time as the sound. One of the easier ways that they put sound into the water was they simply yelled. But another road block they ran into was the ratio of the amount of time it took for the lower frequency waves to penetrate the bubbles walls and access the water around the bubble, and then time from that point to the point on the other end of the body of water. But despite the revolutionary ideas of this article it was left mostly unnoticed. Sonochemistry experienced a renaissance in the 1980s with the advent of inexpensive and reliable generators of high-intensity ultrasound.
   Another significant historical association possessed by Hobe Sound is the brief stay there of former Defense Secretary James Forrestal in 1949 between his resignation from that post and his death.
   The waterphone is a modern invention influenced by a Tibetan drum—encountered by the inventor in the early sixties—containing a small amount of water affecting its timbre. It is also related to the nail violin, which also used a resonator and rods (nails), and is struck or bowed.
  
  Section::::Use.
   Dave Bishop was the drummer of Sharks while they were enjoying the height of their popularity in Hollywood. Bishop used various shapes of cowbell-like instruments in his drumming giving him his unique sound and along with his unusual style of playing. His drum kit had a shark's jaws permanently fastened to the outer drum head of his bass drum facing the crowd.
   Section::::Career.
  
  Section::::Career.:Bass-in-Bridge.
   flow-based musical instruments, such as the hydraulophone, to model empirical observations of some hydraulophones in which obstruction of a water jet for a longer period of time resulted in a buildup in sound level, as water accumulates in a sounding mechanism (reservoir), up to a certain maximum filling point beyond which the sound level reached a maximum, or fell off (along with a slow decay when a water jet was unblocked). Absement has also been used to model artificial muscles, as well as for real muscle interaction in a physical fitness context. Absement has also been used to model human posture.
   The clip is of the professor talking about how water is an object always in motion so to capture it on canvas is a hard task. Guitarist Vadim Taver said in an interview with http://silentstagnation.de/ "This was a good analogy to our music because it's hard to capture the energy, power, and emotion of music on recordings. Sometimes people pull it off, but overall it's not the same as seeing a band perform live, and that was the meaning behind the quote."
   Because its sounding portion is made of glass, the glass harmonica is a type of crystallophone. The phenomenon of rubbing a wet finger around the rim of a wine goblet to produce tones is documented back to Renaissance times; Galileo considered the phenomenon (in his "Two New Sciences"), as did Athanasius Kircher.
   The bell electrical system was also examined for faults because Pettit suggested that the high-pitched noise he'd heard might have been caused by Hoffman’s comms switch going into the water. “The salt water would be going into the speakers and cause the problem in the electronics, causing this high-pitched sound,” he told the Court. But a technician found no electrical fault whatsoever, and Hammond testified that he experienced no electrical shock in the bell.
   Blocking flow through a finger hole directs the water instead to one or more of the above-described sound-production mechanisms, or resulting changes in flow or pressure affect a separate sounding mechanism associated with each finger hole.
  
  Blocking water from coming out of a given hole produces a given note, which, in some embodiments, is electrically amplified by a hydrophone. In one embodiment there is a further processing of each hydrophone signal. Embodiments with various kinds of acoustic or optical pickups are also disclosed.
   We was down in Pahokee, on Lake Okeechobee.. out on a damn pond, fishin' and milkin' snakes .. drinkin' wine, mostly.. This guy down there had a big bell that he's ring to get us all to come in to dinner, an' I'd call over [and] say, 'What's goin' on?' Colored guy said, 'We got twen'y-one drums, we got an old bass horn, an' they even keepin' time on a ding-dong.' See, that was the big bell they'd ring to git us t'come in. 
   Section::::SAW in flow measurement.
   Section::::Echo.
  
  Clapping hands or snapping one’s fingers whilst standing next to perpendicular sheets of corrugated iron (for example, in a fence) will produce a high-pitched echo with a rapidly falling pitch. This is due to a sequence of echoes from adjacent corrugations. 
   The Lloyd mirror effect has been implicated as having an important role in explaining why marine animals such as manatees and whales have been repeatedly hit by boats and ships. Interference due to Lloyd's mirror results in low frequency propeller sounds not being discernible near the surface, where most accidents occur. This is because at the surface, sound reflections are nearly 180 degrees out of phase with the incident waves. Combined with spreading and acoustic shadowing effects, the result is that the marine animal is unable to hear an approaching vessel before it has been run over or entrapped by the hydrodynamic forces of the vessel's passage.
   Entitled "Crab Carillon", the result is a set of 488 tuned chimes, that can be played by pedestrians as they cross the overpass. Each chime is tuned to the note of a melody, composed by Waters. 
  
  The melody is in the form of a [palindrome], to accommodate walking in either direction. 
  
  The music can be heard on the City of San Diego Civic Art Collection
  
  He performs and composes for the "Waters_Bluestone_Duel", a collaboration with percussionist Joel Bluestone that explores the combination of live electronics and percussion, 
   Water valves are often erroneously referred to as "spit valves", as the myth persists that some or much of the liquid consists of spit. Rather, it consists of condensed moisture from the breath of the player. The amount of water accumulated is directly in proportion to the size of the instrument, and the amount of metal exposed to the air, which in turn enables the process of condensation due to warm, moist air from the lungs meeting metal cooled by room-temperature air.
  
  Section::::History and Alternatives.
   As , Bill Baird recorded the song 'Fishtown' at Miner Street Recordings in Philadelphia with Producer and Engineer Brian McTear and Producer Quentin Stoltzfus for Volume 0 Episode 1 of Weathervane Music's documentary video series Shaking Through.
   Section::::History.
  
  Following the First World War, when sonar was first used for the detection of submarines, echo sounders began to find uses outside the military. The French explorer Rallier du Baty reported unexpected midwater echoes, which he attributed to fish schools, in 1927. In 1929, the Japanese scientist Kimura reported disruptions in a continuous acoustic beam by sea bream swimming in an aquaculture pond.
   Several sizes and design variants of the instrument exist. It is generally played in a seated position by a soloist and either bowed or drummed, played as a friction or struck idiophone, with movements to affect the water inside. This combines the resonant characteristics of the bowl and rods in combination with the movement of the water. The sound of the waterphone is often used to evoke mystery and suspense. A superball mallet has become the prime way of drumming the waterphone.
   Besides sounding annoying, motorboating can cause clipping of the audio output waveform, and thus distortion in the output.
  
  Section::::Occurrence.
  
  Although low frequency parasitic oscillations in audio equipment may be due to a range of causes, there are a few types of equipment in which it is frequently seen:
   BULLET::::- Preventing cavitation: When a machine is in contact with a fluid, it may be susceptible to cavitation. The sounds of gas bubbles imploding is the source of the noise. Ships and submarines which have screws that "cavitate" are more vulnerable to detection by sonar.
  
  BULLET::::- Preventing water hammer: In hydraulics and plumbing, water hammer is a known cause for the failure of piping systems. It also generates considerable noise. A valve that abruptly opens or shuts is the most common cause for water hammer.
   Frequency sensitivity underwater also differs significantly to that in air, with a consistently higher threshold of hearing underwater, but also significantly skewed. An underwater noise weighting scale is available to assess noise hazard according to frequency sensitivity for wet conduction.
   As with airborne sound, sound pressure level underwater is usually reported in units of decibels, but there are some important differences that make it difficult (and often inappropriate) to compare SPL in water with SPL in air. These differences include:
  
  BULLET::::- difference in reference pressure: 1 μPa (one micropascal, or one millionth of a pascal) instead of 20 μPa.
  
  BULLET::::- difference in interpretation: there are two schools of thought, one maintaining that pressures should be compared directly, and the other that one should first convert to the intensity of an equivalent plane wave.
   BULLET::::- A third parallel stream investigated how stimulation of these Faraday waves can generate convection and shear in the liquid surrounding bubble.
  
  BULLET::::- In a fourth parallel stream, Leighton investigated how he could use acoustic radiation forces automatically to send these tiny bubbles into cracks and crevices that are normally difficult to penetrate.
  
  BULLET::::- That fourth stream required breakthroughs in a fifth, the way sound propagates down materials containing pores and crevices (leading to the first theory to show why passing ultrasound through different directions in the human ankle could monitor osteoporosis).
   where "K" is the bulk modulus of the fluid.
  
  Section::::Non-gaseous media.:Speed of sound in liquids.:Water.
  
  In fresh water, sound travels at about at (see the External Links section below for online calculators). Applications of underwater sound can be found in sonar, acoustic communication and acoustical oceanography.
  
  Section::::Non-gaseous media.:Speed of sound in liquids.:Seawater.
  