Instruct: Given a question, retrieve passages that can help answer the question.
Query: What is the highest pitch audible to humans?
The generally accepted standard range of audible frequencies for humans is 20 to 20,000Hz,[2][3][4] although the range of frequencies individuals hear is greatly influenced by environmental factors. Frequencies below 20Hz are generally felt rather than heard, assuming the amplitude of the vibration is great enough. High frequencies are the first to be affected by hearing loss due to age or prolonged exposure to very loud noises.[5]
Although pitch notation is intended to describe sounds audibly perceptible as pitches, it can also be used to specify the frequency of non-pitch phenomena. Notes below E or higher than E are outside most humans' hearing range, although notes slightly outside the hearing range on the low end may still be indirectly perceptible as pitches due to their overtones falling within the hearing range. For an example of truly inaudible frequencies, when the Chandra X-ray Observatory observed the waves of pressure fronts propagating away from a black hole, their one oscillation every 10 million years was described by NASA as corresponding to the B fifty-seven octaves below middle C (or B).
Adults can make rasping sounds with their wings and can emit high pitched squeaking sounds that are audible to humans. These sounds have been found to affect bat behavior, as the squeaks of this insect cause bats to avoid the noxious moth. Bats that could associate squeaking or clicking sounds as indicative of toxic prey quickly used sound alone as a deterrent.
Dotted rhythm patterns can be formed by appending a period (".") character to the end of a duration/beat/octave element.The RTTTL format allows octaves starting from the A below middle C and going up four octaves. This corresponds with the inability of cellphones to reproduce certain tones audibly. These octaves are numbered from lowest pitch to highest pitch from 4 to 7.
Minimum audibility curve is a standardized graph of the threshold of hearing frequency for an average human, and is used as the reference level when measuring hearing loss with an audiometer as shown on an audiogram.
The confusion which exists concerning the definition and number of registers is due in part to what takes place in the modal register when a person sings from the lowest pitches of that register to the highest pitches. The frequency of vibration of the vocal folds is determined by their length, tension, and mass. As pitch rises, the vocal folds are lengthened, tension increases, and their thickness decreases. In other words, all three of these factors are in a state of flux in the transition from the lowest to the highest tones.
If the two original frequencies are quite close (for example, a difference of approximately twelve hertz), the frequency of the cosine of the right side of the expression above, that is , is often too low to be perceived as an audible tone or pitch. Instead, it is perceived as a periodic variation in the amplitude of the first term in the expression above. It can be said that the lower frequency cosine term is an "envelope" for the higher frequency one, i.e. that its amplitude is modulated. The frequency of the modulation is , that is, the average of the two frequencies. It can be noted that every second burst in the modulation pattern is inverted. Each peak is replaced by a trough and vice versa. However, because the human ear is not sensitive to the phase of a sound, only its amplitude or intensity, only the magnitude of the envelope is heard. Therefore, subjectively, the frequency of the envelope seems to have twice the frequency of the modulating cosine, which means the audible beat frequency is:
although there is no formal upper or lower limit to this sequence, only a limited number of these pitches are audible to the human ear. 
Pitch class is important because human pitch-perception is periodic: pitches belonging to the same pitch class are perceived as having a similar quality or color, a property called "octave equivalence".
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.
Children can hear some high-pitched sounds that older adults cannot hear, because in humans the upper limit pitch of hearing tends to decrease with age. An American cell phone company has used this to create ring signals that supposedly are only audible to younger humans, but many older people can hear the signals, which may be because of the considerable variation of age-related deterioration in the upper hearing threshold. The Mosquito is an electronic device that uses a high pitched frequency to deter loitering by young people.
Virtual pitch is an experimentally established phenomenon in humans that can be mathematically described. In its basic form, given a series of pure tones whose frequencies correspond to a harmonic series, one will hear a virtual pitch near the fundamental frequency, even if there is no pure tone at that frequency. The perceptual salience (clarity, probability of noticing) of the virtual pitch depends on how closely the audible partials match lower harmonics above the virtual pitch. In Terhardt's pitch algorithm, virtual pitches are predicted by looking for subharmonic coincidences between audible partials in a complex tone - in other words, by looking for missing fundamentals.
Some voice teachers, however, organize registers differently. There are over a dozen different constructs of vocal registers in use within the field. The confusion which exists concerning what a register is, and how many registers there are, is due in part to what takes place in the modal register when a person sings from the lowest pitches of that register to the highest pitches. The frequency of vibration of the vocal folds is determined by their length, tension, and mass. As pitch rises, the vocal folds are lengthened, tension increases, and their thickness decreases. In other words, all three of these factors are in a state of flux in the transition from the lowest to the highest tones.
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.
The singing Tesla coil, sometimes called a zeusaphone, thoramin or musical lightning, is a form of plasma speaker. It is a variation of a solid state Tesla coil that has been modified to produce musical tones by modulating its spark output. The resulting pitch is a low fidelity square wave like sound reminiscent of an analog synthesizer. The high-frequency signal acts in effect as a carrier wave; its frequency is significantly above human-audible sound frequencies, so that digital modulation can reproduce a recognizable pitch. The musical tone results directly from the passage of the spark through the air. Because solid-state coil drivers are limited to "on-off" modulation, the sound produced consists of square-like waveforms rather than sinusoidal (though simple chords are possible).
"Cosmic Pulses" is an exploration of the frontiers between the perceptual realms of pitch and rhythm—visited previously by Stockhausen in "Kontakte" (1958–60)—in which pitches descend below the threshold of pitch perception to become periodic rhythms, and periodic are transformed into audible pitches. It also probes the borders between spatial movement and timbre (, 309–10).
Ultrasound is sound waves with frequencies higher than the upper audible limit of human hearing. Ultrasound is not different from "normal" (audible) sound in its physical properties, except that humans cannot hear it. This limit varies from person to person and is approximately 20 kilohertz (20,000 hertz) in healthy young adults. Ultrasound devices operate with frequencies from 20 kHz up to several gigahertz.
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).
Two methods can be used to measure the minimal audible stimulus and therefore the absolute threshold of hearing.
Minimal audible field involves the subject sitting in a sound field and stimulus being presented via a loudspeaker. The sound level is then measured at the position of the subjects head with the subject not in the sound field.
Minimal audible pressure involves presenting stimuli via headphones or earphones and measuring sound pressure in the subject's ear canal using a very small probe microphone.
The two different methods produce different thresholds and minimal audible field thresholds are often 6 to 10 dB better than minimal audible pressure thresholds. It is thought that this difference is due to:
Minimal audible field and minimal audible pressure are important when considering calibration issues and they also illustrate that the human hearing is most sensitive in the 2–5 kHz range.
However, other researchers claim that the pitch of post-focus words is reduced but sometimes still audible.
Primarily begun in the 1960s, diverse composers have employed divergent methods and styles of process. "A 'musical process' as Christensen defines it is a highly complex dynamic phenomenon involving audible structures that evolve in the course of the musical performance ... 2nd order audible developments, i.e., audible developments within audible developments" . These processes may involve specific systems of choosing and arranging notes through pitch and time, often involving a long term change with a limited amount of musical material, or transformations of musical events that are already relatively complex in themselves. 
An audio frequency (abbreviation: AF) or audible frequency is characterized as a periodic vibration whose frequency is audible to the average human. The SI unit of audio frequency is the hertz (Hz). It is the property of sound that most determines pitch.[1]
Cumaca Cave is a large cave system located in northern of Trinidad, in the southeastern area of the Northern Range. This cave is sometimes also called Oropouche. The caves are home to bats and Oilbirds ("Steatornis caripensis"). These are the only nocturnal fruit eating birds in the world. They forage at night, navigating by echolocation in the same way as bats, but with a high-pitched clicking sound audible to humans.
Pitch depends to a lesser degree on the sound pressure level (loudness, volume) of the tone, especially at frequencies below 1,000 Hz and above 2,000 Hz. The pitch of lower tones gets lower as sound pressure increases. For instance, a tone of 200 Hz that is very loud seems one semitone lower in pitch than if it is just barely audible. Above 2,000 Hz, the pitch gets higher as the sound gets louder. These results were obtained in the pioneering works by S.Stevens and W.Snow . Later investigations, i.e. by A.Cohen, had shown that in most cases the apparent pitch shifts were not significantly different from pitch‐matching errors. When averaged, the remaining shifts followed the directions of Stevens' curves but were small (2% or less by frequency, i.e. not more than a semitone)
Vibrations in the audible frequency range are perceived by humans when air vibrates against their eardrum. Air, or some other vibrating medium such as water, is indispensable in the perception of sound by the human ear. Without it acting as a transmitter, the sound produced by the source will not be perceived by a human.
There is no air in outer space, nor there is any other type of medium capable of transmitting any vibration from a source to a human ear. However, there are sources in outer space that do vibrate at frequencies that would be audible by a human, if only there were some sort of transmitting media to carry those vibrations from the source to a human eardrum.
If only one virtual pitch is perceived in a sound, it is generally the one with the highest salience. The output of Terhardt’s algorithm for pitch perception is a series of virtual pitches of differing salience, of which the most salient is the prediction for “the” pitch of the sound. The existence of several competing virtual pitches can explain the ambiguity of the pitch of many sounds. Bells with non-harmonic spectra are an obvious example (it is often possible to hear the main virtual pitch as the strike tone at the start of the sound, and the main spectral pitch as a hum tone which becomes directly audible as the sound dies away). But Terhardt and his colleagues also demonstrated that regular harmonic complex tones in speech and music are slightly ambiguous in pitch, which may be the ultimate origin of octave equivalence in music and the perceived tonal affinity of successive tones at octave or fifth intervals. 
Terhardt claimed that the root of a chord in western music typically corresponds to its most salient virtual pitch, and that the virtual pitch phenomenon is the ultimate origin of the root effect. He also investigated the perception of roughness in music and claimed that musical consonance and dissonance has two main psychoacoustic components, roughness and harmony, harmony being related to the perception of virtual pitch.