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21,000 | After a quarrel with Zeus, Hera left him and retreated to Euboea, and no word from Zeus managed to sway her mind. Cithaeron, the local king, then advised Zeus to take a wooden statue of a woman, wrap it up, and pretend to marry it. Zeus did as told, claiming "she" was Plataea, Asopus's daughter. Hera, once she heard th... | https://en.wikipedia.org/wiki?curid=13208 |
21,001 | According to Diodorus Siculus, Alcmene, the mother of Heracles, was the very last mortal woman Zeus ever slept with; following the birth of Heracles, he ceased to beget humans altogether. | https://en.wikipedia.org/wiki?curid=13208 |
21,002 | Hera is the stepmother and enemy of Heracles. The name Heracles means "Glory of Hera". In Homer's "Iliad", when Alcmene was about to give birth to Heracles, Zeus announced to all the gods that on that day a child by Zeus himself, would be born and rule all those around him. Hera, after requesting Zeus to swear an oath ... | https://en.wikipedia.org/wiki?curid=13208 |
21,003 | Hera's wrath against Zeus' son continues and while Heracles is still an infant, Hera sends two serpents to kill him as he lies in his cot. Heracles throttles the snakes with his bare hands and is found by his nurse playing with their limp bodies as if they were a child's toy. | https://en.wikipedia.org/wiki?curid=13208 |
21,004 | One account of the origin of the Milky Way is that Zeus had tricked Hera into nursing the infant Heracles: discovering who he was, she pulled him from her breast, and a spurt of her milk formed the smear across the sky that can be seen to this day. Unlike any Greeks, the Etruscans instead pictured a full-grown bearded ... | https://en.wikipedia.org/wiki?curid=13208 |
21,005 | When Heracles reached adulthood, Hera drove him mad, which led him to murder his family and this later led to him undertaking his famous labours. Hera assigned Heracles to labour for King Eurystheus at Mycenae. She attempted to make almost all of Heracles' twelve labours more difficult. When he fought the Lernaean Hydr... | https://en.wikipedia.org/wiki?curid=13208 |
21,006 | Eurystheus also wanted to sacrifice the Cretan Bull to Hera. She refused the sacrifice because it reflected glory on Heracles. The bull was released and wandered to Marathon, becoming known as the Marathonian Bull. | https://en.wikipedia.org/wiki?curid=13208 |
21,007 | Some myths state that in the end, Heracles befriended Hera by saving her from Porphyrion, a giant who tried to rape her during the Gigantomachy, and that she even gave her daughter Hebe as his bride. Whatever myth-making served to account for an archaic representation of Heracles as "Hera's man" it was thought suitable... | https://en.wikipedia.org/wiki?curid=13208 |
21,008 | When Hera discovered that Leto was pregnant and that Zeus was the father, she convinced the nature spirits to prevent Leto from giving birth on terra-firma, the mainland, any island at sea, or any place under the sun. Poseidon gave pity to Leto and guided her to the floating island of Delos, which was neither mainland ... | https://en.wikipedia.org/wiki?curid=13208 |
21,009 | Either way, Artemis was born first and then assisted with the birth of Apollo. Some versions say Artemis helped her mother give birth to Apollo for nine days. Another variation states that Artemis was born one day before Apollo, on the island of Ortygia and that she helped Leto cross the sea to Delos the next day to gi... | https://en.wikipedia.org/wiki?curid=13208 |
21,010 | This account of the birth of Apollo and Artemis is contradicted by Hesiod in Theogony, as the twins are born prior to Zeus’ marriage to Hera. | https://en.wikipedia.org/wiki?curid=13208 |
21,011 | The myth of Io has many forms and embellishments. Generally, Io was a priestess of Hera at the Heraion of Argos. Zeus lusted after her and either Hera turned Io into a heifer to hide her from Zeus, or Zeus did so to hide her from Hera but was discovered. Hera had Io tethered to an olive-tree and set Argus Panoptes () t... | https://en.wikipedia.org/wiki?curid=13208 |
21,012 | A prophecy stated that a son of the sea-nymph Thetis, with whom Zeus fell in love after gazing upon her in the oceans off the Greek coast, would become greater than his father. Possibly for this reason, Thetis was betrothed to an elderly human king, Peleus son of Aeacus, either upon Zeus' orders, or because she wished ... | https://en.wikipedia.org/wiki?curid=13208 |
21,013 | The goddesses quarreled bitterly over it, and none of the other gods would venture an opinion favoring one, for fear of earning the enmity of the other two. They chose to place the matter before Zeus, who, not wanting to favor one of the goddesses, put the choice into the hands of Paris, a Trojan prince. After bathing ... | https://en.wikipedia.org/wiki?curid=13208 |
21,014 | Hera plays a substantial role in "The Iliad", appearing in several books throughout the epic poem. She hates the Trojans because of Paris' decision that Aphrodite was the most beautiful goddess, and so supports the Greeks during the war. Throughout the epic, Hera makes many attempts to thwart the Trojan army. In books ... | https://en.wikipedia.org/wiki?curid=13208 |
21,015 | In book 5, Hera and Athena plot to harm Ares, who had been seen by Diomedes in assisting the Trojans. Diomedes called for his soldiers to fall back slowly. Hera, Ares' mother, saw Ares' interference and asked Zeus, Ares' father, for permission to drive Ares away from the battlefield. Hera encouraged Diomedes to attack ... | https://en.wikipedia.org/wiki?curid=13208 |
21,016 | In book 8, Hera tries to persuade Poseidon to disobey Zeus and help the Achaean army. He refuses, saying he doesn't want to go against Zeus. Determined to intervene in the war, Hera and Athena head to the battlefield. However, seeing the two flee, Zeus sent Iris to intercept them and make them return to Mount Olympus o... | https://en.wikipedia.org/wiki?curid=13208 |
21,017 | In book 14 Hera devises a plan to deceive Zeus. Zeus set a decree that the gods were not allowed to interfere in the mortal war. Hera is on the side of the Achaeans, so she plans a Deception of Zeus where she seduces him, with help from Aphrodite, and tricks him into a deep sleep, with the help of Hypnos, so that the G... | https://en.wikipedia.org/wiki?curid=13208 |
21,018 | In book 21, Hera continues her interference with the battle as she tells Hephaestus to prevent the river from harming Achilles. Hephaestus sets the battlefield ablaze, causing the river to plead with Hera, promising her he will not help the Trojans if Hephaestus stops his attack. Hephaestus stops his assault and Hera r... | https://en.wikipedia.org/wiki?curid=13208 |
21,019 | When Hera learned that Semele, daughter of Cadmus King of Thebes, was pregnant by Zeus, she disguised herself as Semele's nurse and persuaded the princess to insist that Zeus show himself to her in his true form. When he was compelled to do so, having sworn by Styx, his thunder and lightning destroyed Semele. Zeus took... | https://en.wikipedia.org/wiki?curid=13208 |
21,020 | In another version, Dionysus was originally the son of Zeus by either Demeter or Persephone. Hera sent her Titans to rip the baby apart, from which he was called Zagreus ("Torn in Pieces"). Zeus rescued the heart; or, the heart was saved, variously, by Athena, Rhea, or Demeter. Zeus used the heart to recreate Dionysus ... | https://en.wikipedia.org/wiki?curid=13208 |
21,021 | Lamia was a lovely queen of Libya, whom Zeus loved and slept with. Hera in jealousy robbed Lamia of her children, either by kidnapping and hiding them away, killing them, or causing Lamia herself to kill her own offspring. Lamia became disfigured from the torment, transforming into a terrifying being who hunted and kil... | https://en.wikipedia.org/wiki?curid=13208 |
21,022 | Gerana was a queen of the Pygmies who boasted she was more beautiful than Hera. The wrathful goddess turned her into a crane and proclaimed that her bird descendants should wage eternal war on the Pygmy folk. | https://en.wikipedia.org/wiki?curid=13208 |
21,023 | Cydippe, a priestess of Hera, was on her way to a festival in the goddess' honor. The oxen which were to pull her cart were overdue and her sons, Biton and Cleobis, pulled the cart the entire way (45 stadia, 8 kilometers). Cydippe was impressed with their devotion to her and Hera, and so asked Hera to give her children... | https://en.wikipedia.org/wiki?curid=13208 |
21,024 | This honor bestowed upon the children was later used by Solon as proof when trying to convince Croesus that it is impossible to judge a person's happiness until they have died a fruitful death after a joyous life. | https://en.wikipedia.org/wiki?curid=13208 |
21,025 | Tiresias was a priest of Zeus, and as a young man, he encountered two snakes mating and hit them with a stick. He was then transformed into a woman. As a woman, Tiresias became a priestess of Hera, married, and had children, including Manto. After seven years as a woman, Tiresias again found mating snakes; depending on... | https://en.wikipedia.org/wiki?curid=13208 |
21,026 | As a result of his experiences, Zeus and Hera asked him to settle the question of which sex, male or female, experienced more pleasure during intercourse. Zeus claimed it was women; Hera claimed it was men. When Tiresias sided with Zeus, Hera struck him blind. Since Zeus could not undo what she had done, he gave him th... | https://en.wikipedia.org/wiki?curid=13208 |
21,027 | An alternative and less commonly told story has it that Tiresias was blinded by Athena after he stumbled onto her bathing naked. His mother, Chariclo, begged her to undo her curse, but Athena could not; she gave him a prophecy instead. | https://en.wikipedia.org/wiki?curid=13208 |
21,028 | At the marriage of Zeus and Hera, a nymph named Chelone was disrespectful or refused to attend the wedding. Zeus thus turned her into a tortoise. | https://en.wikipedia.org/wiki?curid=13208 |
21,029 | Hera hated Pelias because he had killed Sidero, his step-grandmother, in one of the goddess's temples. She later convinced Jason and Medea to kill Pelias. The Golden Fleece was the item that Jason needed to get his mother freed. | https://en.wikipedia.org/wiki?curid=13208 |
21,030 | When Zeus had pity on Ixion and brought him to Olympus and introduced him to the gods, instead of being grateful, Ixion grew lustful for Hera. Zeus found out about his intentions and made a cloud in the shape of Hera, who was later named Nephele, and tricked Ixion into coupling with it. From their union came Centaurus.... | https://en.wikipedia.org/wiki?curid=13208 |
21,031 | The speed of sound is the distance travelled per unit of time by a sound wave as it propagates through an elastic medium. At , the speed of sound in air is about , or one kilometre in or one mile in . It depends strongly on temperature as well as the medium through which a sound wave is propagating. At , the speed of s... | https://en.wikipedia.org/wiki?curid=147853 |
21,032 | The speed of sound in an ideal gas depends only on its temperature and composition. The speed has a weak dependence on frequency and pressure in ordinary air, deviating slightly from ideal behavior. | https://en.wikipedia.org/wiki?curid=147853 |
21,033 | In colloquial speech, "speed of sound" refers to the speed of sound waves in air. However, the speed of sound varies from substance to substance: typically, sound travels most slowly in gases, faster in liquids, and fastest in solids. For example, while sound travels at in air, it travels at in water (almost 4.3 times ... | https://en.wikipedia.org/wiki?curid=147853 |
21,034 | Sound waves in solids are composed of compression waves (just as in gases and liquids), and a different type of sound wave called a shear wave, which occurs only in solids. Shear waves in solids usually travel at different speeds than compression waves, as exhibited in seismology. The speed of compression waves in soli... | https://en.wikipedia.org/wiki?curid=147853 |
21,035 | In fluid dynamics, the speed of sound in a fluid medium (gas or liquid) is used as a relative measure for the speed of an object moving through the medium. The ratio of the speed of an object to the speed of sound (in the same medium) is called the object's Mach number. Objects moving at speeds greater than the speed o... | https://en.wikipedia.org/wiki?curid=147853 |
21,036 | Sir Isaac Newton's 1687 "Principia" includes a computation of the speed of sound in air as . This is too low by about 15%. The discrepancy is due primarily to neglecting the (then unknown) effect of rapidly-fluctuating temperature in a sound wave (in modern terms, sound wave compression and expansion of air is an adiab... | https://en.wikipedia.org/wiki?curid=147853 |
21,037 | During the 17th century there were several attempts to measure the speed of sound accurately, including attempts by Marin Mersenne in 1630 (1,380 Parisian feet per second), Pierre Gassendi in 1635 (1,473 Parisian feet per second) and Robert Boyle (1,125 Parisian feet per second). In 1709, the Reverend William Derham, R... | https://en.wikipedia.org/wiki?curid=147853 |
21,038 | Derham used a telescope from the tower of the church of St. Laurence, Upminster to observe the flash of a distant shotgun being fired, and then measured the time until he heard the gunshot with a half-second pendulum. Measurements were made of gunshots from a number of local landmarks, including North Ockendon church. ... | https://en.wikipedia.org/wiki?curid=147853 |
21,039 | The transmission of sound can be illustrated by using a model consisting of an array of spherical objects interconnected by springs. | https://en.wikipedia.org/wiki?curid=147853 |
21,040 | In real material terms, the spheres represent the material's molecules and the springs represent the bonds between them. Sound passes through the system by compressing and expanding the springs, transmitting the acoustic energy to neighboring spheres. This helps transmit the energy in-turn to the neighboring sphere's s... | https://en.wikipedia.org/wiki?curid=147853 |
21,041 | The speed of sound through the model depends on the stiffness/rigidity of the springs, and the mass of the spheres. As long as the spacing of the spheres remains constant, stiffer springs/bonds transmit energy quicker, while larger spheres transmit the energy slower. | https://en.wikipedia.org/wiki?curid=147853 |
21,042 | In a real material, the stiffness of the springs is known as the "elastic modulus", and the mass corresponds to the material density. Given that all other things being equal (ceteris paribus), sound will travel slower in spongy materials, and faster in stiffer ones. Effects like dispersion and reflection can also be un... | https://en.wikipedia.org/wiki?curid=147853 |
21,043 | For instance, sound will travel 1.59 times faster in nickel than in bronze, due to the greater stiffness of nickel at about the same density. Similarly, sound travels about 1.41 times faster in light hydrogen (protium) gas than in heavy hydrogen (deuterium) gas, since deuterium has similar properties but twice the dens... | https://en.wikipedia.org/wiki?curid=147853 |
21,044 | Some textbooks mistakenly state that the speed of sound increases with density. This notion is illustrated by presenting data for three materials, such as air, water, and steel; they each have vastly different compressibility, which more than makes up for the density differences. An illustrative example of the two effe... | https://en.wikipedia.org/wiki?curid=147853 |
21,045 | A practical example can be observed in Edinburgh when the "One o'Clock Gun" is fired at the eastern end of Edinburgh Castle. Standing at the base of the western end of the Castle Rock, the sound of the Gun can be heard through the rock, slightly before it arrives by the air route, partly delayed by the slightly longer ... | https://en.wikipedia.org/wiki?curid=147853 |
21,046 | In a gas or liquid, sound consists of compression waves. In solids, waves propagate as two different types. A longitudinal wave is associated with compression and decompression in the direction of travel, and is the same process in gases and liquids, with an analogous compression-type wave in solids. Only compression w... | https://en.wikipedia.org/wiki?curid=147853 |
21,047 | These different waves (compression waves and the different polarizations of shear waves) may have different speeds at the same frequency. Therefore, they arrive at an observer at different times, an extreme example being an earthquake, where sharp compression waves arrive first and rocking transverse waves seconds late... | https://en.wikipedia.org/wiki?curid=147853 |
21,048 | The speed of a compression wave in a fluid is determined by the medium's compressibility and density. In solids, the compression waves are analogous to those in fluids, depending on compressibility and density, but with the additional factor of shear modulus which affects compression waves due to off-axis elastic energ... | https://en.wikipedia.org/wiki?curid=147853 |
21,049 | The speed of sound in mathematical notation is conventionally represented by "c", from the Latin "celeritas" meaning "velocity". | https://en.wikipedia.org/wiki?curid=147853 |
21,050 | Thus, the speed of sound increases with the stiffness (the resistance of an elastic body to deformation by an applied force) of the material and decreases with an increase in density. For ideal gases, the bulk modulus "K" is simply the gas pressure multiplied by the dimensionless adiabatic index, which is about 1.4 for... | https://en.wikipedia.org/wiki?curid=147853 |
21,051 | For general equations of state, if classical mechanics is used, the speed of sound "c" can be derived as follows: | https://en.wikipedia.org/wiki?curid=147853 |
21,052 | Consider the sound wave propagating at speed formula_3 through a pipe aligned with the formula_4 axis and with a cross-sectional area of formula_5. In time interval formula_6 it moves length formula_7. In steady state, the mass flow rate formula_8 must be the same at the two ends of the tube, therefore the mass flux fo... | https://en.wikipedia.org/wiki?curid=147853 |
21,053 | If relativistic effects are important, the speed of sound is calculated from the relativistic Euler equations. | https://en.wikipedia.org/wiki?curid=147853 |
21,054 | In a non-dispersive medium, the speed of sound is independent of sound frequency, so the speeds of energy transport and sound propagation are the same for all frequencies. Air, a mixture of oxygen and nitrogen, constitutes a non-dispersive medium. However, air does contain a small amount of CO which "is" a dispersive m... | https://en.wikipedia.org/wiki?curid=147853 |
21,055 | In a dispersive medium, the speed of sound is a function of sound frequency, through the dispersion relation. Each frequency component propagates at its own speed, called the phase velocity, while the energy of the disturbance propagates at the group velocity. The same phenomenon occurs with light waves; see optical di... | https://en.wikipedia.org/wiki?curid=147853 |
21,056 | The speed of sound is variable and depends on the properties of the substance through which the wave is travelling. In solids, the speed of transverse (or shear) waves depends on the shear deformation under shear stress (called the shear modulus), and the density of the medium. Longitudinal (or compression) waves in so... | https://en.wikipedia.org/wiki?curid=147853 |
21,057 | In fluids, only the medium's compressibility and density are the important factors, since fluids do not transmit shear stresses. In heterogeneous fluids, such as a liquid filled with gas bubbles, the density of the liquid and the compressibility of the gas affect the speed of sound in an additive manner, as demonstrate... | https://en.wikipedia.org/wiki?curid=147853 |
21,058 | In gases, adiabatic compressibility is directly related to pressure through the heat capacity ratio (adiabatic index), while pressure and density are inversely related to the temperature and molecular weight, thus making only the completely independent properties of "temperature and molecular structure" important (heat... | https://en.wikipedia.org/wiki?curid=147853 |
21,059 | Sound propagates faster in low molecular weight gases such as helium than it does in heavier gases such as xenon. For monatomic gases, the speed of sound is about 75% of the mean speed that the atoms move in that gas. | https://en.wikipedia.org/wiki?curid=147853 |
21,060 | For a given ideal gas the molecular composition is fixed, and thus the speed of sound depends only on its temperature. At a constant temperature, the gas pressure has no effect on the speed of sound, since the density will increase, and since pressure and density (also proportional to pressure) have equal but opposite ... | https://en.wikipedia.org/wiki?curid=147853 |
21,061 | In non-ideal gas behavior regimen, for which the Van der Waals gas equation would be used, the proportionality is not exact, and there is a slight dependence of sound velocity on the gas pressure. | https://en.wikipedia.org/wiki?curid=147853 |
21,062 | Humidity has a small but measurable effect on the speed of sound (causing it to increase by about 0.1%–0.6%), because oxygen and nitrogen molecules of the air are replaced by lighter molecules of water. This is a simple mixing effect. | https://en.wikipedia.org/wiki?curid=147853 |
21,063 | In the Earth's atmosphere, the chief factor affecting the speed of sound is the temperature. For a given ideal gas with constant heat capacity and composition, the speed of sound is dependent "solely" upon temperature; see "" below. In such an ideal case, the effects of decreased density and decreased pressure of altit... | https://en.wikipedia.org/wiki?curid=147853 |
21,064 | Since temperature (and thus the speed of sound) decreases with increasing altitude up to , sound is refracted upward, away from listeners on the ground, creating an acoustic shadow at some distance from the source. The decrease of the speed of sound with height is referred to as a negative sound speed gradient. | https://en.wikipedia.org/wiki?curid=147853 |
21,065 | However, there are variations in this trend above . In particular, in the stratosphere above about , the speed of sound increases with height, due to an increase in temperature from heating within the ozone layer. This produces a positive speed of sound gradient in this region. Still another region of positive gradient... | https://en.wikipedia.org/wiki?curid=147853 |
21,066 | For an ideal gas, "K" (the bulk modulus in equations above, equivalent to "C", the coefficient of stiffness in solids) is given by | https://en.wikipedia.org/wiki?curid=147853 |
21,067 | Using the ideal gas law to replace "p" with "nRT"/"V", and replacing "ρ" with "nM"/"V", the equation for an ideal gas becomes | https://en.wikipedia.org/wiki?curid=147853 |
21,068 | This equation applies only when the sound wave is a small perturbation on the ambient condition, and the certain other noted conditions are fulfilled, as noted below. Calculated values for "c" have been found to vary slightly from experimentally determined values. | https://en.wikipedia.org/wiki?curid=147853 |
21,069 | Newton famously considered the speed of sound before most of the development of thermodynamics and so incorrectly used isothermal calculations instead of adiabatic. His result was missing the factor of "γ" but was otherwise correct. | https://en.wikipedia.org/wiki?curid=147853 |
21,070 | Numerical substitution of the above values gives the ideal gas approximation of sound velocity for gases, which is accurate at relatively low gas pressures and densities (for air, this includes standard Earth sea-level conditions). Also, for diatomic gases the use of requires that the gas exists in a temperature range ... | https://en.wikipedia.org/wiki?curid=147853 |
21,071 | In addition, we switch to the Celsius temperature , which is useful to calculate air speed in the region near | https://en.wikipedia.org/wiki?curid=147853 |
21,072 | A graph comparing results of the two equations is to the right, using the slightly more accurate value of for the speed of sound at . | https://en.wikipedia.org/wiki?curid=147853 |
21,073 | The speed of sound varies with temperature. Since temperature and sound velocity normally decrease with increasing altitude, sound is refracted upward, away from listeners on the ground, creating an acoustic shadow at some distance from the source. Wind shear of 4 m/(s · km) can produce refraction equal to a typical te... | https://en.wikipedia.org/wiki?curid=147853 |
21,074 | For sound propagation, the exponential variation of wind speed with height can be defined as follows: | https://en.wikipedia.org/wiki?curid=147853 |
21,075 | In the 1862 American Civil War Battle of Iuka, an acoustic shadow, believed to have been enhanced by a northeast wind, kept two divisions of Union soldiers out of the battle, because they could not hear the sounds of battle only (six miles) downwind. | https://en.wikipedia.org/wiki?curid=147853 |
21,076 | In fact, assuming an ideal gas, the speed of sound "c" depends on temperature and composition only, not on the pressure or density (since these change in lockstep for a given temperature and cancel out). Air is almost an ideal gas. The temperature of the air varies with altitude, giving the following variations in the ... | https://en.wikipedia.org/wiki?curid=147853 |
21,077 | The medium in which a sound wave is travelling does not always respond adiabatically, and as a result, the speed of sound can vary with frequency. | https://en.wikipedia.org/wiki?curid=147853 |
21,078 | The limitations of the concept of speed of sound due to extreme attenuation are also of concern. The attenuation which exists at sea level for high frequencies applies to successively lower frequencies as atmospheric pressure decreases, or as the mean free path increases. For this reason, the concept of speed of sound ... | https://en.wikipedia.org/wiki?curid=147853 |
21,079 | The molecular composition of the gas contributes both as the mass (M) of the molecules, and their heat capacities, and so both have an influence on speed of sound. In general, at the same molecular mass, monatomic gases have slightly higher speed of sound (over 9% higher) because they have a higher "γ" (...) than diato... | https://en.wikipedia.org/wiki?curid=147853 |
21,080 | This gives the 9% difference, and would be a typical ratio for speeds of sound at room temperature in helium vs. deuterium, each with a molecular weight of 4. Sound travels faster in helium than deuterium because adiabatic compression heats helium more since the helium molecules can store heat energy from compression o... | https://en.wikipedia.org/wiki?curid=147853 |
21,081 | Note that in this example we have assumed that temperature is low enough that heat capacities are not influenced by molecular vibration (see heat capacity). However, vibrational modes simply cause gammas which decrease toward 1, since vibration modes in a polyatomic gas give the gas additional ways to store heat which ... | https://en.wikipedia.org/wiki?curid=147853 |
21,082 | By far, the most important factor influencing the speed of sound in air is temperature. The speed is proportional to the square root of the absolute temperature, giving an increase of about per degree Celsius. For this reason, the pitch of a musical wind instrument increases as its temperature increases. | https://en.wikipedia.org/wiki?curid=147853 |
21,083 | The speed of sound is raised by humidity. The difference between 0% and 100% humidity is about at standard pressure and temperature, but the size of the humidity effect increases dramatically with temperature. | https://en.wikipedia.org/wiki?curid=147853 |
21,084 | The dependence on frequency and pressure are normally insignificant in practical applications. In dry air, the speed of sound increases by about as the frequency rises from to . For audible frequencies above it is relatively constant. Standard values of the speed of sound are quoted in the limit of low frequencies, whe... | https://en.wikipedia.org/wiki?curid=147853 |
21,085 | As shown above, the approximate value 1000/3 = 333.33... m/s is exact a little below 5 °C and is a good approximation for all "usual" outside temperatures (in temperate climates, at least), hence the usual rule of thumb to determine how far lightning has struck: count the seconds from the start of the lightning flash t... | https://en.wikipedia.org/wiki?curid=147853 |
21,086 | Mach number, a useful quantity in aerodynamics, is the ratio of air speed to the local speed of sound. At altitude, for reasons explained, Mach number is a function of temperature. | https://en.wikipedia.org/wiki?curid=147853 |
21,087 | Aircraft flight instruments, however, operate using pressure differential to compute Mach number, not temperature. The assumption is that a particular pressure represents a particular altitude and, therefore, a standard temperature. Aircraft flight instruments need to operate this way because the stagnation pressure se... | https://en.wikipedia.org/wiki?curid=147853 |
21,088 | The earliest reasonably accurate estimate of the speed of sound in air was made by William Derham and acknowledged by Isaac Newton. Derham had a telescope at the top of the tower of the Church of St Laurence in Upminster, England. On a calm day, a synchronized pocket watch would be given to an assistant who would fire ... | https://en.wikipedia.org/wiki?curid=147853 |
21,089 | The simplest concept is the measurement made using two microphones and a fast recording device such as a digital storage scope. This method uses the following idea. | https://en.wikipedia.org/wiki?curid=147853 |
21,090 | If a sound source and two microphones are arranged in a straight line, with the sound source at one end, then the following can be measured: | https://en.wikipedia.org/wiki?curid=147853 |
21,091 | In these methods, the time measurement has been replaced by a measurement of the inverse of time (frequency). | https://en.wikipedia.org/wiki?curid=147853 |
21,092 | Kundt's tube is an example of an experiment which can be used to measure the speed of sound in a small volume. It has the advantage of being able to measure the speed of sound in any gas. This method uses a powder to make the nodes and antinodes visible to the human eye. This is an example of a compact experimental set... | https://en.wikipedia.org/wiki?curid=147853 |
21,093 | A tuning fork can be held near the mouth of a long pipe which is dipping into a barrel of water. In this system it is the case that the pipe can be brought to resonance if the length of the air column in the pipe is equal to "(1 + 2"n")λ/4" where "n" is an integer. As the antinodal point for the pipe at the open end is... | https://en.wikipedia.org/wiki?curid=147853 |
21,094 | The effect of impurities can be significant when making high-precision measurements. Chemical desiccants can be used to dry the air, but will, in turn, contaminate the sample. The air can be dried cryogenically, but this has the effect of removing the carbon dioxide as well; therefore many high-precision measurements a... | https://en.wikipedia.org/wiki?curid=147853 |
21,095 | In a solid, there is a non-zero stiffness both for volumetric deformations and shear deformations. Hence, it is possible to generate sound waves with different velocities dependent | https://en.wikipedia.org/wiki?curid=147853 |
21,096 | on the deformation mode. Sound waves generating volumetric deformations (compression) and shear deformations (shearing) are called pressure waves (longitudinal waves) and shear waves (transverse waves), respectively. In earthquakes, the corresponding seismic waves are called P-waves (primary waves) and S-waves (seconda... | https://en.wikipedia.org/wiki?curid=147853 |
21,097 | The last quantity is not an independent one, as . Note that the speed of pressure waves depends both on the pressure and shear resistance properties of the material, while the speed of shear waves depends on the shear properties only. | https://en.wikipedia.org/wiki?curid=147853 |
21,098 | Typically, pressure waves travel faster in materials than do shear waves, and in earthquakes this is the reason that the onset of an earthquake is often preceded by a quick upward-downward shock, before arrival of waves that produce a side-to-side motion. For example, for a typical steel alloy, , and , yielding a compr... | https://en.wikipedia.org/wiki?curid=147853 |
21,099 | Speed of sound in semiconductor solids can be very sensitive to the amount of electronic dopant in them. | https://en.wikipedia.org/wiki?curid=147853 |
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