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Concept: Vocal folds


Vocal folds are used as sound sources in various species, but it is unknown how vocal fold morphologies are optimized for different acoustic objectives. Here we identify two main variables affecting range of vocal fold vibration frequency, namely vocal fold elongation and tissue fiber stress. A simple vibrating string model is used to predict fundamental frequency ranges across species of different vocal fold sizes. While average fundamental frequency is predominantly determined by vocal fold length (larynx size), range of fundamental frequency is facilitated by (1) laryngeal muscles that control elongation and by (2) nonlinearity in tissue fiber tension. One adaptation that would increase fundamental frequency range is greater freedom in joint rotation or gliding of two cartilages (thyroid and cricoid), so that vocal fold length change is maximized. Alternatively, tissue layers can develop to bear a disproportionate fiber tension (i.e., a ligament with high density collagen fibers), increasing the fundamental frequency range and thereby vocal versatility. The range of fundamental frequency across species is thus not simply one-dimensional, but can be conceptualized as the dependent variable in a multi-dimensional morphospace. In humans, this could allow for variations that could be clinically important for voice therapy and vocal fold repair. Alternative solutions could also have importance in vocal training for singing and other highly-skilled vocalizations.

Concepts: Acoustics, Human voice, Larynx, Phonation, Vocal folds, Phonetics, Fundamental frequency, Histology of the Vocal Folds


Freddie Mercury was one of the twentieth century’s best-known singers of commercial contemporary music. This study presents an acoustical analysis of his voice production and singing style, based on perceptual and quantitative analysis of publicly available sound recordings. Analysis of six interviews revealed a median speaking fundamental frequency of 117.3 Hz, which is typically found for a baritone voice. Analysis of voice tracks isolated from full band recordings suggested that the singing voice range was 37 semitones within the pitch range of F#2 (about 92.2 Hz) to G5 (about 784 Hz). Evidence for higher phonations up to a fundamental frequency of 1,347 Hz was not deemed reliable. Analysis of 240 sustained notes from 21 a-cappella recordings revealed a surprisingly high mean fundamental frequency modulation rate (vibrato) of 7.0 Hz, reaching the range of vocal tremor. Quantitative analysis utilizing a newly introduced parameter to assess the regularity of vocal vibrato corroborated its perceptually irregular nature, suggesting that vibrato (ir)regularity is a distinctive feature of the singing voice. Imitation of subharmonic phonation samples by a professional rock singer, documented by endoscopic high-speed video at 4,132 frames per second, revealed a 3:1 frequency locked vibratory pattern of vocal folds and ventricular folds.

Concepts: Acoustics, Human voice, Phonation, Vocal folds, Singing, Vocal range, Voice type, A cappella


Background: Iranian vibrato (tahrir) is a common feature of traditional Iranian singing. A unique feature of tahrir is a modulated voice quality perceived as a rhythmic falsetto voice break associated with upward pitch inflections. Laryngeal discomfort and impaired voice quality can occur in singers when they perform Iranian tahrir using an improper technique. Aim: A case series research design was used to explore voice treatment outcomes using laryngeal manual therapy (LMT) for treating voice problems associated with tahrir singing. Method: Four professional Iranian singers of the traditional style (3 men and 1 woman) were studied. All subjects reported difficulty executing tahrir during performances. They were assessed by a speech-language pathologist (SLP) specializing in the administration of LMT for voice disorders. Multidimensional assessments were made of the participants' vocal function using acoustic and auditory-perceptual evaluation, self-reports of the singers, and LMT assessments by the SLP before and after treatment. The therapeutic program implemented LMT techniques to release laryngeal joints and reduce muscular tension. Results: Pretreatment examination of the larynx and anterior neck musculature using palpation showed that the difficulties in producing tahrir vibrato were associated with a decreased thyrohyoid space and tension in the submental complex and sternocleidomastoid. Posttreatment examination showed an increased thyrohyoid space and reduced tension in the submental complex and sternocleidomastoid, associated with the singers' perception of reduced effort producing tahrir vibrato during singing. Conclusion: Tahrir vibrato requires specific training to prevent excessive tension in laryngeal and neck muscles. In the absence of such training, or in the context of excessive singing associated with fatigue, LMT may facilitate more efficient vocal production in tahrir singers. © 2015 S. Karger AG, Basel.

Concepts: Muscle, Human voice, Larynx, Phonation, Vocal folds, Singing, Vocal range, Chest voice



Elephants can communicate using sounds below the range of human hearing (“infrasounds” below 20 hertz). It is commonly speculated that these vocalizations are produced in the larynx, either by neurally controlled muscle twitching (as in cat purring) or by flow-induced self-sustained vibrations of the vocal folds (as in human speech and song). We used direct high-speed video observations of an excised elephant larynx to demonstrate flow-induced self-sustained vocal fold vibration in the absence of any neural signals, thus excluding the need for any “purring” mechanism. The observed physical principles of voice production apply to a wide variety of mammals, extending across a remarkably large range of fundamental frequencies and body sizes, spanning more than five orders of magnitude.

Concepts: Acoustics, Ultrasound, Human voice, Larynx, Phonation, Vocal folds, Frequency, Sound


Shifts in healthy human microbial communities have now been linked to disease in numerous body sites. Noninvasive swabbing remains the sampling technique of choice in most locations; however, it is not well known if this method samples the entire community, or only those members that are easily removed from the surface. We sought to compare the communities found via swabbing and biopsied tissue in true vocal folds, a location that is difficult to sample without causing potential damage and impairment to tissue function. A secondary aim of this study was to determine if swab sampling of the false vocal folds could be used as proxy for true vocal folds. True and false vocal fold mucosal samples (swabbed and biopsied) were collected from six pigs and used for 454 pyrosequencing of the V3-V5 region of the 16S rRNA gene. Most of the alpha and beta measures of diversity were found to be significantly similar between swabbed and biopsied tissue samples. Similarly, the communities found in true and false vocal folds did not differ considerably. These results suggest that samples taken via swabs are sufficient to assess the community, and that samples taken from the false vocal folds may be used as proxies for the true vocal folds. Assessment of these techniques opens an avenue to less traumatic means to explore the role microbes play in the development of diseases of the vocal folds, and perhaps the rest of the respiratory tract.

Concepts: Sample, Sample size, Sampling, Ribosomal RNA, 16S ribosomal RNA, Larynx, Vocal folds, Cluster sampling


Acoustic and perceptual studies show a number of differences between the voices of radio performers and controls. Despite this, the vocal fold kinematics underlying these differences are largely unknown. Using high-speed videoendoscopy, this study sought to determine whether the vocal vibration features of radio performers differed from those of non-performing controls.

Concepts: Human voice, Vocal folds, Cultural studies, Quantity, Histology of the Vocal Folds


The proper development of the vocal cords requires embryos to contain a certain number of progenitor cells, and mutations that lead to an overflow of cells can cause malformations of the voice box.

Concepts: Embryo, Developmental biology, Progenitor cell, Human voice, Larynx, Phonation, Vocal folds, Phonetics


Laryngeal hypersensitivity may be an important component of the common disorders of laryngeal motor dysfunction including chronic refractory cough, pdoxical vocal fold movement (vocal cord dysfunction), muscle tension dysphonia, and globus pharyngeus. Patients with these conditions frequently report sensory disturbances, and an emerging concept of the ‘irritable larynx’ suggests common features of a sensory neuropathic dysfunction as a part of these disorders. The aim of this study was to develop a Laryngeal Hypersensitivity Questionnaire for patients with laryngeal dysfunction syndromes in order to measure the laryngeal sensory disturbance occurring in these conditions.

Concepts: Asthma, Human voice, Larynx, Phonation, Vocal folds, Phonetics, Globus pharyngis, Vocal cord dysfunction


In previous research, acoustic characteristics of the male voice have been shown to signal various aspects of mate quality and threat potential. But the human voice is also a medium of linguistic communication. The present study explores whether physical and vocal indicators of male mate quality and threat potential are linked to effective communicative behaviors such as vowel differentiation and use of more salient phonetic variants of consonants. We show that physical and vocal indicators of male threat potential, height and formant position, are negatively linked to vowel space size, and that height and levels of circulating testosterone are negatively linked to the use of the aspirated variant of the alveolar stop consonant /t/. Thus, taller, more masculine men display less clarity in their speech and prefer phonetic variants that may be associated with masculine attributes such as toughness. These findings suggest that vocal signals of men’s mate quality and/or dominance are not confined to the realm of voice acoustics but extend to other aspects of communicative behavior, even if this means a trade-off with speech patterns that are considered communicatively advantageous, such as clarity and indexical cues to higher social class.

Concepts: Consonant, Human voice, Phonation, Vocal folds, International Phonetic Alphabet, Phonetics, Singing, Vowel