Instruct: Given a question, retrieve relevant passages that can help answer the question.
Query: What is the highest pitch audible to humans?
In 1959, Harman Kardon marketed the Citation II, an early ultra wideband stereophonic tube amplifier. Designed by Stewart Hegeman, it featured 60 watts/channel output with a frequency response of 18-60,000 Hz at 20 watt output. The company promoted their philosophy of designing high fidelity sound using amplifiers that provided widest possible audio bandwidth. Although the human ear highest audible range is around 20,000 Hz, the full range of sound goes beyond that with harmonics and overtones that may be beyond the hearing range of the human ear. These harmonics interact with other frequencies to produce audible secondary sounds or interference. Harman Kardon promoted the design in audio magazines and product brochures.
The boiling point of water is typically considered to be 100 °C or 212 °F. Pressure and a change in the composition of the liquid may alter the boiling point of the liquid. For this reason, high elevation cooking generally takes longer since boiling point is a function of atmospheric pressure. In Denver, Colorado, USA, which is at an elevation of about one mile, water boils at approximately 95 °C or 203 °F. Depending on the type of food and the elevation, the boiling water may not be hot enough to cook the food properly. Similarly, increasing the pressure as in a pressure cooker raises the temperature of the contents above the open air boiling point.
Electric sound recording and reproduction are electrical or mechanical techniques and devices for the inscription and re-creation of sound waves, such as spoken voice, singing, instrumental music, or sound effects. Acoustic analog recording is achieved by a small microphone diaphragm that can record sound waves on a phonograph (in which a stylus senses grooves on a record) or magnetic tape. The first practical sound recording and reproduction device was the mechanical phonograph cylinder, invented by Thomas Edison in 1877 and patented in 1878. 
The next major technical development was the invention of the gramophone disc in 1889. For much of the 20th century, records were the most common way of selling sound recordings. The widespread availability of records and the development of radio broadcasting enabled a much larger proportion of people to listen to songs and pieces performed by the top artists, enabling the development of national and even international musical stars. In the 1970s, the compact cassette became a major consumer audio format. Advances in electronic and mechanical miniaturization led to the development of the Sony Walkman, a pocket-sized cassette player introduced in 1979, which allowed consumers to listen to their favourite albums outside of their home.
Morse is still widely used by amateur radio operators (hams). Experienced hams routinely send Morse at 20 words per minute, using manually operated hand telegraph keys; enthusiasts such as members of The CW Operators' Club routinely send and receive Morse code at speeds up to 60 wpm. The upper limit for Morse operators attempting to write down Morse code received by ear using paper and pencil is roughly 20 wpm. Many skilled Morse code operators can receive Morse code by ear mentally without writing down the information at speeds up to 70 wpm. To write down the Morse code information manually at speeds higher than 20 wpm it is usual for the operators to use a typewriter or computer keyboard to enable higher speed copying.
All remaining species of the family Felidae (‘purring cats’) have a completely ossified hyoid, which enables them to purr but not to roar. Based on a technical acoustic definition of roaring, the presence of this vocalization type depends on specific characteristics of the vocal folds and an elongated vocal tract, which is rendered possible by an incompletely ossified hyoid.Purring may have developed as an evolutionary advantage as a signalling mechanism of reassurance between mother cats and nursing kittens. Post-nursing cats often purr as a sign of contentment: when being petted, becoming relaxed, or eating. Some purring may be a signal to another animal that the purring cat does not pose a threat.
While direct measurement of the most violent tornado wind speeds is nearly impossible, since conventional anemometers would be destroyed by the intense winds and flying debris, some tornadoes have been scanned by mobile Doppler radar units, which can provide a good estimate of the tornado's winds. The highest wind speed ever measured in a tornado, which is also the highest wind speed ever recorded on the planet, is 301 ± 20 mph (484 ± 32 km/h) in the F5 Bridge Creek-Moore, Oklahoma, tornado which killed 36 people. Though the reading was taken about above the ground, this is a testament to the power of the strongest tornadoes.
In May 2007, the Caudwell Xtreme Everest undertook a medical study of oxygen levels in human blood at extreme altitude. Over 200 volunteers climbed to Everest Base Camp where various medical tests were performed to examine blood oxygen levels. A small team also performed tests on the way to the summit. Even at base camp, the low partial pressure of oxygen had direct effect on blood oxygen saturation levels. At sea level, blood oxygen saturation is generally 98–99%. At base camp, blood saturation fell to between 85 and 87%. Blood samples taken at the summit indicated very low oxygen levels in the blood. A side effect of low blood oxygen is a greatly increased breathing rate, often 80–90 breaths per minute as opposed to a more typical 20–30. Exhaustion can occur merely attempting to breathe.
The highest mountains above sea level are generally not the highest above the surrounding terrain. There is no precise definition of surrounding base, but Denali, Mount Kilimanjaro and Nanga Parbat are possible candidates for the tallest mountain on land by this measure. The bases of mountain islands are below sea level, and given this consideration Mauna Kea ( above sea level) is the world's tallest mountain and volcano, rising about from the Pacific Ocean floor. Ojos del Salado has the greatest rise on Earth— from the summit to the bottom of the Atacama Trench about away, though most of this rise is not part of the mountain.
Radio frequency radiation is usually measured in kilohertz (kHz), megahertz (MHz), or gigahertz (GHz). Light is electromagnetic radiation that is even higher in frequency, and has frequencies in the range of tens (infrared) to thousands (ultraviolet) of terahertz. Electromagnetic radiation with frequencies in the low terahertz range (intermediate between those of the highest normally usable radio frequencies and long-wave infrared light) is often called terahertz radiation. Even higher frequencies exist, such as that of gamma rays, which can be measured in exahertz (EHz). (For historical reasons, the frequencies of light and higher frequency electromagnetic radiation are more commonly specified in terms of their wavelengths or photon energies: for a more detailed treatment of this and the above frequency ranges, see electromagnetic spectrum.)
The flute is one of the oldest and most widely used wind instruments. The precursors of the modern concert flute were keyless wooden transverse flutes similar to modern fifes. These were later modified to include between one and eight keys for chromatic notes.
In the human body at birth, there are over 270 bones, but many of these fuse together during development, leaving a total of 206 separate bones in the adult, not counting numerous small sesamoid bones. The largest bone in the body is the femur or thigh-bone, and the smallest is the stapes in the middle ear.
Pikes Peak is the highest summit of the southern Front Range of the Rocky Mountains, in North America. The ultra-prominent fourteener is located in Pike National Forest, west of downtown Colorado Springs, Colorado. The mountain is named in honor of American explorer Zebulon Pike, who was unable to reach the summit. The summit is higher than any point in the United States east of its longitude.
The first microphone that enabled proper voice telephony was the (loose-contact) carbon microphone (then called transmitter). This was independently developed around 1878 by David Edward Hughes in England and Emile Berliner and Thomas Edison in the US. Although Edison was awarded the first patent in mid-1877, Hughes had demonstrated his working device in front of many witnesses some years earlier, and most historians credit him with its invention.
A cricket bat is a specialised piece of equipment used by batsmen in the sport of cricket to hit the ball, typically consisting of a cane handle attached to a flat-fronted willow-wood blade. The length of the bat may be no more than 38 inches (965 mm) and the width no more than 4.25 inches (108 mm). Its use is first mentioned in 1624. Since 1979, a rule change stipulated that bats can only be made from wood.
Mates can recognize each other by their calls. Researchers have analyzed calls of blue-footed boobies and conducted playback experiments. Although calls differed between sexes, unique individual signatures were present. It was found that both males and females can discriminate the calls of their mates from others.
Ultrasound has been used in Medicine for close to half a century and its safety has been studied for almost the same period of time. In 1992, the US FDA first allowed the use of ultrasound at a frequency of 1.6 MHz in a toothbrush. In 1993, the American Institute of Ultrasound in Medicine (AIUM), in conjunction with the National Electrical Manufacturers Association (NEMA) developed the Output Display Standard (ODS), including the thermal index and mechanical index which have been incorporated into the FDA’s new regulations. These regulations limit the power output of these devices to a level low enough to avoid raising surrounding tissue temperature by more than 1 °C.
Heights of mountains are typically measured above sea level. Using this metric, Mount Everest is the highest mountain on Earth, at . There are at least 100 mountains with heights of over above sea level, all of which are located in central and southern Asia. The highest mountains above sea level are generally not the highest above the surrounding terrain. There is no precise definition of surrounding base, but Denali, Mount Kilimanjaro and Nanga Parbat are possible candidates for the tallest mountain on land by this measure. The bases of mountain islands are below sea level, and given this consideration Mauna Kea ( above sea level) is the world's tallest mountain and volcano, rising about from the Pacific Ocean floor.
The wolf pack howls on average for 85 seconds. It is usually started by a single wolf, after which other wolves may join in. The pack leader, the alpha wolf, usually uses a lower-pitched howl and howls more frequently than wolves standing on the lower rungs of the pack's hierarchy. Although some functions of the howling are still unknown by scientists, they believe that wolves may howl to scare off other wolf packs from their territory and to gather their own pack, as wolves possess perfect hearing and their howling can be heard for up to in the forest and in open space. Researchers have found a relationship between the number of times a wolf howls and the strength of their relationship with other pack members. According to Friederike Range, co-director of the University of Vienna's Wolf Science Center, "the strength of the relationship between wolves predicted how many times a wolf howled."
It has been postulated that domestic cats can learn to manipulate their owners through vocalizations that are similar to the cries of human babies. Some cats learn to add a purr to the vocalization, which makes it less harmonious and more dissonant to humans, and therefore harder to ignore. Individual cats learn to make these vocalizations through trial-and-error; when a particular vocalization elicits a positive response from a human, the probability increases that the cat will use that vocalization in the future.
The stapes is the third bone of the three ossicles in the middle ear. The stapes is a stirrup-shaped bone, and the smallest in the human body. It rests on the oval window, to which it is connected by an annular ligament. The stapes is described as having a base, resting on the oval window, as well as a head that articulates with the incus. These are connected by anterior and posterior limbs (). The stapes articulates with the incus through the incudostapedial joint. The stapes is the smallest bone in the human body, and measures roughly 3 x 2.5mm, greater along the head-base span.
VHF Radio waves do not travel far beyond the visual horizon, so reception distances for FM stations are usually limited to 30–40 miles (50–65 km) They can also be blocked by hills or buildings.
"" (K. 316/300b) is a recitative and aria for soprano and orchestra that Wolfgang Amadeus Mozart wrote for Aloysia Weber. It is famous for including two occurrences of a G, i.e. the G above high C, or 1568 Hz by modern concert pitch – according to the "Guinness Book of Records", the highest musical note ever scored for the human voice. (However, an A is scored in Ignaz Umlauf's "Das Irrlicht", also sung by Aloysia Weber.)
There has been an industry trend towards sampling rates well beyond the basic requirements: such as 96 kHz and even 192 kHz This is in contrast with laboratory experiments, which have failed to show that ultrasonic frequencies are audible to human observers. In fact, in some cases, ultrasonic sounds do interact with and modulate the audible part of the frequency spectrum (intermodulation distortion), "degrading" the fidelity. One advantage of higher sampling rates is that they can relax the low-pass filter design requirements for ADCs and DACs, but with modern oversampling sigma-delta converters this advantage is less important.
The AY-3-8910 generates tones with base frequencies of up to 125 kHz (4 MHz input clock, or 8 MHz with the YM2149F), well beyond human perception and into the ultrasonic range. The existence of ultrasonic values is a consequence of the frequency-divider design; in order to have adequate resolution at audible frequencies it is necessary for the overall clock rate (and thus the output at small divisors) to be considerably higher than the audible range. Only divisors below 5 give entirely-ultrasonic output frequencies. Frequencies equivalent to the top octave of a piano keyboard can be defined with reasonable accuracy versus the accepted note values for the even-tempered scale, to nearly 1 Hz precision in the A440 range and even more finely at lower pitches. Despite the high maximum frequency, the ability to divide that figure by 4096 means the lowest directly definable output frequency is 30.6 Hz, roughly equal to B0, the third lowest note on a normal 88-key piano, and as good as subsonic with everyday speaker systems. In essence, the chip is able to produce decently musical output at all reasonable pitches found in most compositions.
Using scientific pitch notation consistently, the MIDI NoteOn message assigns MIDI note 0 to C (five octaves below C or Middle C; lowest note on the two largest organs of the world; about one octave below the human hearing threshold: its overtones, however, are audible), MIDI note 21 to A (the bottom key of an 88-key piano), MIDI note 60 to C (Middle C), MIDI note 69 to A (A440), MIDI note 108 to C (the top key of an 88-key piano), and MIDI note 127 to G (beyond the piano; one octave above the highest note on some keyboard glockenspiels; some notes above the highest-pitched organ pipes).