Question: William Vennard, was a famous American vocal pedagogist, Vennard introduced contemporary scientific research in the areas of human anatomy and physiology into the study of singing, the shift in approach led to the rejection of many of the beliefs and practices held since the bel canto era, most particularly in the areas of what, which term used for a range of tones in the human voice produced by a particular vibratory pattern of the vocal folds?

Context articles: William Vennard
Vocal fry register
Ray Smolover
Voice type
Human voice
Coup de glotte
Vocal register
Electroglottograph
Faucalized voice
Vocal fold nodule

William Vennard (31 January 1909 Normal, Illinois – 10 January 1971 Los Angeles, California) was a famous American vocal pedagogist who devoted his life to researching the human voice and its use in singing.
 He was one of the driving forces behind a major shift within the field of vocal pedagogy during the middle of the 20th century.
 Along with a few other American singing teachers, such as Ralph Appelman at Indiana University, Vennard introduced contemporary scientific research in the areas of human anatomy and physiology into the study of singing.
 This shift in approach led to the rejection of many of the beliefs and practices held since the bel canto era, most particularly in the areas of vocal registration and vocal resonation.
 Vennard was renowned as an excellent teacher whose written works have influenced generations of singers, vocal pedagogues and voice scientists.
 He taught many successful singers including acclaimed mezzo-soprano Marilyn Horne, who studied under him at the University of Southern California.
The vocal fry register (also known as pulse register, laryngealization, pulse phonation, creak, croak, popcorning, glottal fry, glottal rattle, glottal scrape, or strohbass) is the lowest vocal register and is produced through a loose glottal closure which will permit air to bubble through slowly with a popping or rattling sound of a very low frequency.
 During this phonation, the arytenoid cartilages in the larynx are drawn together which causes the vocal folds to compress rather tightly and become relatively slack and compact.
 This process forms a large and irregularly vibrating mass within the vocal folds that produces the characteristic low popping or rattling sound when air passes through the glottal closure.
 The register (if well controlled) can extend far below the modal voice register, in some cases up to 8 octaves lower, such as in the case of Tim Storms who holds the world record for lowest frequency note ever produced by a human, a G−7, which is only 0.189 Hz.
 Humans however can only hear sounds down to 12 Hz under ideal conditions.
Itzchok Reev "Ray" Smolover (January 15, 1921 – September 11, 2015) was an American vocal pedagogist, voice teacher, tenor, opera librettist, opera director, and hazzan.
 He was a graduate of Carnegie Mellon University and Columbia University.
 One of his notable students was Richard Kiley.
 He is the author of several publications on the art of singing, including "The Singer’s Handbook", "Vocal Behavior Analysis and Modification", and "Sing Your Best".
A voice type is a particular human singing voice identified as having certain qualities or characteristics of vocal range, vocal weight, tessitura, vocal timbre, and vocal transition points ("passaggio"), such as breaks and lifts within the voice.
 Other considerations are physical characteristics, speech level, scientific testing, and vocal register.
 A singer's voice type is identified by a process known as voice classification, by which the human voice is evaluated and thereby designated into a particular voice type.
 The discipline of voice classification developed within European classical music and is not generally applicable to other forms of singing.
 Voice classification is often used within opera to associate possible roles with potential voices.
 Several different voice classification systems are available to identify voice types, including the German "Fach" system and the choral music system among many others; no system is universally applied or accepted.
The human voice consists of sound made by a human being using the vocal folds for talking, singing, laughing, crying, screaming, etc.
 The human voice frequency is specifically a part of human sound production in which the vocal folds (vocal cords) are the primary sound source.
 (Other sound production mechanisms produced from the same general area of the body involve the production of unvoiced consonants, clicks, whistling and whispering.)
 Generally speaking, the mechanism for generating the human voice can be subdivided into three parts; the lungs, the vocal folds within the larynx, and the articulators.
 The lung (the pump) must produce adequate airflow and air pressure to vibrate vocal folds (this air pressure is the fuel of the voice).
 The vocal folds (vocal cords) are a vibrating valve that chops up the airflow from the lungs into audible pulses that form the laryngeal sound source.
 The muscles of the larynx adjust the length and tension of the vocal folds to ‘fine-tune’ pitch and tone.
 The articulators (the parts of the vocal tract above the larynx consisting of tongue, palate, cheek, lips, etc.) articulate and filter the sound emanating from the larynx and to some degree can interact with the laryngeal airflow to strengthen it or weaken it as a sound source.
Coup de glotte or 'shock of the glottis' is a term used in the theory of singing technique to describe a particular method of emitting or opening a note by an abrupt physical mechanism of the glottis (the space between the vocal folds).
 During the 19th century there was disagreement among teachers and performers as to whether the technique should be taught as a normal part of vocal method or not.
 The technique is still sometimes used to achieve particular effects, dramatic or ornamental, but is usually avoided in the teaching of fundamental vocal method.
 In English, it is often called a glottal attack.
A vocal register is a range of tones in the human voice produced by a particular vibratory pattern of the vocal folds.
 These registers include modal voice (or normal voice), vocal fry, falsetto, and the whistle register.
The electroglottograph, or EGG, (also referred to as a laryngograph) is a device used for the noninvasive measurement of the degree of contact between the vibrating vocal folds during voice production.
 Though it is difficult to verify the assumption precisely, the aspect of contact being measured by a typical EGG unit is considered to be the vocal fold contact area (VFCA).
 To measure VFCA, an electrodes are applied on the surface of the neck so that the EGG records variations in the transverse electrical impedance of the larynx and nearby tissues by means of a small A/C electric current (in megaHertz).
 This electrical impedance will vary slightly with the area of contact between the moist vocal folds during the setment of the glottal vibratory cycle in which the folds are in contact.
 However, because the percentage variation in the neck impedance caused by vocal fold contact can be extremely small and varies considerably between subjects, no absolute measure of contact area is obtained, only the pattern of variation for a given subject.
Faucalized voice, also called hollow voice or yawny voice, is a vocal quality of speech production characterized by the vertical expansion of the pharyngeal cavity due to the lowering of the larynx.
 It is termed "faucalized" because of the stretching of the fauces and visible narrowing of the faucial pillars in the back of the oral cavity.
 During faucalized voice, the sides of pharynx expand outward and the larynx descends and tilts forward.
 The term "yawny voice" is appropriate to compare this voice quality to the physiological act of yawning.
 Its opposite is "harsh voice", a vocal quality produced when the pharynx is contracted and the larynx raised.
 Faucalized voice is not to be confused with "breathy voice", which involves relaxed vocal folds, greater velocity of airflow through the glottis and produces a lower pitch sound.
 Faucalized voice involves the forward tilting of the larynx which stretches the vocal folds and produces a higher pitch sound, despite the increased volume of the pharyngeal cavity.
Vocal fold nodules are bilaterally symmetrical benign white masses that form at the midpoint of the vocal folds.
 Although diagnosis involves a physical examination of the head and neck, as well as perceptual voice measures, visualization of the vocal nodules via laryngeal endoscopy remains the primary diagnostic method.
 Vocal fold nodules interfere with the vibratory characteristics of the vocal folds by increasing the mass of the vocal folds and changing the configuration of the vocal fold closure pattern.
 Due to these changes, the quality of the voice may be affected.
 As such, the major perceptual signs of vocal fold nodules include vocal hoarseness and breathiness.
 Other common symptoms include vocal fatigue, soreness or pain lateral to the larynx, and reduced frequency and intensity range.
 Airflow levels during speech may also be increased.
 Vocal fold nodules are thought to be the result of vocal fold tissue trauma caused by excessive mechanical stress, including repeated or chronic vocal overuse, abuse, or misuse.
 Predisposing factors include profession, gender, dehydration, respiratory infection, and other inflammatory factors.