Human voice
The human voice  consists of sound made by a human being using the vocal folds for talking, singing, laughing, crying, screaming, etc.  Human voice is specifically that part of human sound production in which the vocal folds (vocal cords) are the primary noise source.  Generally speaking, the voice can be subdivided into three parts; the lungs, the vocal folds, and the articulators.  The lung (the pump) must produce adequate airflow to vibrate vocal folds (air is the fuel of the voice). The vocal folds (vocal cords) are the vibrators, neuromuscular units that fine tune pitch & tone.  The articulators (vocal tract consisting of tongue, palate, cheek, lips, etc.) articulate and filter the sound.
The vocal folds, in combination with the articulators, are capable of producing highly intricate arrays of sound.
The tone of voice may be modulated to suggest emotions such as anger, surprise, or happiness.
Singers use the human voice as an instrument for creating music.

# Voice types and the folds (cords) themselves
Men and women have different vocal folds sizes; adult male voices are usually lower-pitched and have larger folds. The male vocal folds (which would be measured vertically in the opposite diagram), are between 17 mm and 25 mm in length.
Matching the female body, which on the whole has less muscle than the male, females have smaller folds. The female vocal folds are between 12.5 mm and 17.5 mm in length.
As seen in the illustration, the folds are located just above the trachea (the windpipe which travels from the lungs). Food and drink do not pass through the cords but instead pass through the esophagus, an unlinked tube. Both tubes are separated by the epiglottis, a "flap" that covers the opening of the trachea while swallowing. When food goes down through the cords and trachea (can occur when a person inhales while swallowing), aspiration and possibly choking result.
The folds in both sexes are within the larynx. They are attached at the back (side nearest the spinal cord) to the arytenoid cartilages, and at the front (side under the chin) to the thyroid cartilage. They have no outer edge as they blend into the side of the breathing tube (the illustration is out of date and does not show this well) while their inner edges or "margins" are free to vibrate (the hole). They have a three layer construction of an epithelium, vocal ligament, then muscle (vocalis muscle), which can shorten and bulge the folds. They are flat triangular bands and are pearly white in color. Above both sides of the vocal cord is the vestibular fold or false vocal cord, which has a small sac between its two folds (not illustrated).
The difference in vocal folds size between men and women means that they have differently pitched voices. Additionally, genetics also causes variances amongst the same sex, with men and women's singing voices being categorized into types. For example, among men, there are basses, baritones and tenors, and contraltos, mezzo-sopranos and sopranos among women. There are additional categories for operatic voices, see voice type.  This is not the only source of difference between male and female voice.  Men, generally speaking, have a larger vocal tract, which essentially gives the resultant voice a lower tonal quality.  This is mostly independent of the vocal folds themselves.

# Physiology and vocal timbre
The sound of each individual's voice is entirely unique not only because of the actual shape and size of an individual's vocal cords but also due to the size and shape of the rest of that person's body. Humans have vocal folds which can loosen, tighten, or change their thickness, and over which breath can be transferred at varying pressures. The shape of chest and neck, the position of the tongue, and the tightness of otherwise unrelated muscles can be altered. Any one of these actions results in a change in pitch, volume, timbre, or tone of the sound produced. Sound also resonates within different parts of the body, and an individual's size and bone structure can affect the sound produced by an individual.
Singers can also learn to project sound in certain ways so that it resonates better within their vocal tract. This is known as vocal resonation. Another major influence on vocal sound and production is the function of the larynx which people can manipulate in different ways to produce different sounds. These different kinds of laryngeal function are described as different kinds of vocal registers. The primary method for singers to accomplish this is through the use of the Singer's Formant; which has been shown to match particularly well to the most sensitive part of the ear's frequency range.

## Vocal registration
Vocal registration refers to the system of vocal registers within the human voice. A register in the human voice is a particular series of tones, produced in the same vibratory pattern of the vocal folds, and possessing the same quality. Registers originate in laryngeal function. They occur because the vocal folds are capable of producing several different vibratory patterns. Each of these vibratory patterns appears within a particular range of pitches and produces certain characteristic sounds. The term register can be somewhat confusing at it encompasses several aspects of the human voice. The term register can be used to refer to any of the following:
- A particular part of the vocal range such as the upper, middle, or lower registers.
- A resonance area such as chest voice or head voice.
- A phonatory process
- A certain vocal timbre
- A region of the voice which is defined or delimited by vocal breaks.
- A subset of a language used for a particular purpose or in a particular social setting.
In linguistics, a register language is a language which combines tone and vowel phonation into a single phonological system.
Within speech pathology the term vocal register has three constituent elements: a certain vibratory pattern of the vocal folds, a certain series of pitches, and a certain type of sound. Speech pathologists identify four vocal registers based on the physiology of laryngeal function: the vocal fry register, the modal register, the falsetto register, and the whistle register. This view is also adopted by many vocal pedagogists.

## Vocal resonation
Vocal resonation is the process by which the basic product of phonation is enhanced in timbre and/or intensity by the air-filled cavities through which it passes on its way to the outside air. Various terms related to the resonation process include amplification, enrichment, enlargement, improvement, intensification, and prolongation, although in strictly scientific usage acoustic authorities would question most of them. The main point to be drawn from these terms by a singer or speaker is that the end result of resonation is, or should be, to make a better sound.
There are seven areas that may be listed as possible vocal resonators. In sequence from the lowest within the body to the highest, these areas are the chest, the tracheal tree, the larynx itself, the pharynx, the oral cavity, the nasal cavity, and the sinuses.

# Influences of the human voice
The twelve tone musical scale, upon which the majority of the world's music is based, may have its roots in the sound of the human voice during the course of evolution, according to a study published by the New Scientist. Analysis of recorded speech samples found peaks in acoustic energy that mirrored the distances between notes in the twelve-tone scale.

# Voice disorders
There are many disorders which affect the human voice; these include speech impediments, and growths and |lesions on the vocal folds. Talking improperly for long periods of time causes vocal loading which is stress inflicted on the speech organs. When vocal injury is done, often a ENT specialist may be able to help, but the best treatment is the prevention of injuries through good vocal production. Voice therapy is generally delivered by a Speech-language pathologist
Hoarseness or breathiness that lasts for more than two weeks is a common symptom for an underlying voice disorder and should be investigated medically.

# Footnotes
-  Titze, I. R. (2008). The human instrument. Sci.Am. 298 (1):94-101. PM 18225701
-  Titze, I.R. (1994). Principles of Voice Production, Prentice Hall (currently published by NCVS.org), ISBN 978-0137178933.
-  Titze, I. R. (2006).The Myoelatic Aerodynamic Theory of Phonation, Iowa City:National Center for Voice and Speech, 2006.
-  Smith BL, Brown BL, Strong WJ, Rencher AC. (1975) Effects of speech rate on personality perception. Lang Speech. 18(2):145-52 PMID: 1195957
-  Williams CE, Stevens KN.(1972). Emotions and speech: some acoustical correlates. J Acoust Soc Am. 52(4):1238-50 PMID: 4638039
-  I. R. Titze, S. Mapes, and B. Story. (1994) Acoustics of the Tenor High Voice. J.Acoust.Soc.Am. 95 (2):1133-1142. PMID: 8132903
-  Thurman, Leon & Welch, ed., Graham (2000), Bodymind & voice: Foundations of voice education (revised ed.), Collegeville, Minnesota: The VoiceCare Network et al., ISBN 0874141230
-  Vennard, William (1967). Singing: The Mechanism and the Technic. Carl Fischer. ISBN 13: 978-0825800559 Check |isbn= value: invalid character (help)..mw-parser-output cite.citation{font-style:inherit}.mw-parser-output q{quotes:"\"""\"""'""'"}.mw-parser-output code.cs1-code{color:inherit;background:inherit;border:inherit;padding:inherit}.mw-parser-output .cs1-lock-free a{background:url("")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-lock-limited a,.mw-parser-output .cs1-lock-registration a{background:url("")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-lock-subscription a{background:url("")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration{color:#555}.mw-parser-output .cs1-subscription span,.mw-parser-output .cs1-registration span{border-bottom:1px dotted;cursor:help}.mw-parser-output .cs1-hidden-error{display:none;font-size:100%}.mw-parser-output .cs1-visible-error{display:none;font-size:100%}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration,.mw-parser-output .cs1-format{font-size:95%}.mw-parser-output .cs1-kern-left,.mw-parser-output .cs1-kern-wl-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right,.mw-parser-output .cs1-kern-wl-right{padding-right:0.2em}
-  E. J. Hunter and I. R. Titze. Overlap of Hearing and Voicing Ranges in Singing. J.Singing 61 (4):387-392, 2004.
-  E. J. Hunter, J. G. Svec, and I. R. Titze. Comparison of the Produced and Perceived Voice Range Profiles in Untrained and Trained Classical Singers. J.Voice  2005.
-  Large, John (1972). "Towards an Integrated Physiologic-Acoustic Theory of Vocal Registers". The NATS Bulletin. 28: 3035. Unknown parameter |month= ignored (help)
-  Jump up to: 12.0 12.1 12.2 McKinney, James (1994). The Diagnosis and Correction of Vocal Faults. Genovex Music Group. ISBN 13: 978-1565939400 Check |isbn= value: invalid character (help).
-  Greene, Margaret (2001). The Voice and its Disorders. John Wiley & Sons; 6th Edition edition. ISBN 13: 978-1861561961 Check |isbn= value: invalid character (help). Unknown parameter |coauthors= ignored (help)
-  Musical roots may lie in human voice - 06 August 2003 - New Scientist

# Further reading
- Puts, D. A., Gaulin, S. J. C., & Verdolini, K. (2006). Dominance and the evolution of sexual dimorphism in human voice pitch. Evolution and Human Behavior, 27: 283-296. Full text
- Titze, I. R. (2008). The human instrument. Sci.Am. 298 (1):94-101. PM 18225701
- Thurman, Leon & Welch, ed., Graham (2000), Bodymind & voice: Foundations of voice education (revised ed.), Collegeville, Minnesota: The VoiceCare Network et al., ISBN 0874141230