electroglottograph 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 assum ...

ic wavegram (short: EGG wavegram) is a tool for analyzing the voice source in speech and singing, based on electroglottographic (EGG)

signals A signal is both the process and the result of Signal transmission, transmission of data over some transmission media, media accomplished by embedding some variation. Signals are important in multiple subject fields including signal processin ...

(and their first

derivative In mathematics, the derivative is a fundamental tool that quantifies the sensitivity to change of a function's output with respect to its input. The derivative of a function of a single variable at a chosen input value, when it exists, is t ...

, DEGG).

Assessing the singing and speaking voice

The wavegram, invented by Christian T. Herbst, provides an intuitive means for quickly assessing

vocal fold In humans, the vocal cords, also known as vocal folds, are folds of throat tissues that are key in creating sounds through Speech, vocalization. The length of the vocal cords affects the pitch of voice, similar to a violin string. Open when brea ...

contact phenomena and their variation over time. Vocal fold closings and openings appear here as a sequence of events rather than single incidents, taking place over a certain period of time, and changing with pitch, loudness and

register Register or registration may refer to: Arts, entertainment, and media Music * Register (music), the relative "height" or range of a note, melody, part, instrument, etc. * ''Register'', a 2017 album by Travis Miller * Registration (organ), ...

. Wavegrams document systematic phenomena, indicating subtle changes of the vocal fold

oscillatory Oscillation is the repetitive or periodic variation, typically in time, of some measure about a central value (often a point of equilibrium) or between two or more different states. Familiar examples of oscillation include a swinging pendulum ...

regime. Electroglottographic wavegrams are created in 5 steps (see illustration): # extraction of consecutive glottal cycles from the EGG signal; # locally normalized data values are converted into

monochrome A monochrome or monochromatic image, object or palette is composed of one color (or values of one color). Images using only shades of grey are called grayscale (typically digital) or black-and-white (typically analog). In physics, mon ...

color information, and are plotted as a strip representing one glottal cycle each; # strips are rotated 90 degrees counter-clockwise; # Glottal cycle duration is normalized by

scaling Scaling may refer to: Science and technology Mathematics and physics * Scaling (geometry), a linear transformation that enlarges or diminishes objects * Scale invariance, a feature of objects or laws that do not change if scales of length, energ ...

the individual glottal cycle plots to the same height; # the resulting graphs are combined to form the final display, the EGG wavegram. Wavegram data can be influenced by # the anatomical baseline of the individual; #

physiological Physiology (; ) is the science, scientific study of function (biology), functions and mechanism (biology), mechanisms in a life, living system. As a branches of science, subdiscipline of biology, physiology focuses on how organisms, organ syst ...

and habitual muscular patterns in

phonation The term phonation has slightly different meanings depending on the subfield of phonetics. Among some phoneticians, ''phonation'' is the process by which the vocal folds produce certain sounds through quasi-periodic vibration. This is the defi ...

, e.g. degree of vocal fold

adduction Motion, the process of movement, is described using specific anatomical terms. Motion includes movement of organs, joints, limbs, and specific sections of the body. The terminology used describes this motion according to its direction relativ ...

, register in singing and speech; # organic

voice disorders Voice disordersTitze, I.R. (1994). Principles of Voice Production, Prentice Hall, . are medical conditions involving abnormal pitch, loudness or quality of the sound produced by the larynx and thereby affecting speech production. These include: * ...

, i.e.

pathological Pathology is the study of disease. The word ''pathology'' also refers to the study of disease in general, incorporating a wide range of biology research fields and medical practices. However, when used in the context of modern medical treatme ...

deviations from the norm. Wavegrams show a potential to be used in: * screenings for voice disorders (e.g. in schools); * (real-time) bio-feedback in voice pedagogy and education; *

voice therapy Voice therapy consists of techniques and procedures that target vocal parameters, such as vocal fold closure, pitch, volume, and quality. This therapy is provided by speech-language pathologists and is primarily used to aid in the management of ...

(functional voice disorders); * conservative and post-operative treatment of organic voice disorders; * voice recognition in forensics. To construct a wavegram, the time-varying

fundamental frequency The fundamental frequency, often referred to simply as the ''fundamental'' (abbreviated as 0 or 1 ), is defined as the lowest frequency of a Periodic signal, periodic waveform. In music, the fundamental is the musical pitch (music), pitch of a n ...

is calculated and consecutive individual glottal cycles are identified in the EGG or DEGG signal. Each cycle is locally normalized in duration and amplitude, the signal values are encoded by color intensity and the cycles are concatenated to display the entire phonation in a single image, much as in sound spectrography. The idea of wavegrams can be extended to displaying other data, such as acoustic signals or high-speed video

endoscopic An endoscopy is a procedure used in medicine to look inside the body. The endoscopy procedure uses an endoscope to examine the interior of a hollow organ or cavity of the body. Unlike many other medical imaging techniques, endoscopes are insert ...

recordings of the vibrating vocal folds.Unger, J., Meyer, T., Herbst, C. T., Döllinger, M., and Lohscheller, J. (2011). "''PVG-Wavegramm: Dreidimensionale Visualisierung von Stimmlippendynamik''", in 28. Wissenschaftliche Jahrestagung der Deutschen Gesellschaft für Phoniatrie und Pädaudiologie e. V. (Zurich, Switzerland). – http://www.egms.de/static/en/meetings/dgpp2011/11dgpp40.shtml

References

External links

Proceedings of the 5th International Conference on the Physiology and Acoustics of Singing (PAS5), Stockholm, Sweden
{{Webarchive, url=https://web.archive.org/web/20120329201815/http://www.speech.kth.se/pas5/pas5_programme.pdf , date=2012-03-29
The Voice Foundation's 40th Annual Symposium: Care of the Professional Voice, 2011, Philadelphia, PA

7th International Workshop on Models and Analysis of Vocal Emissions for Biomedical Applications (MAVEBA), August 2011, Firenze, Italy
Voice technology Human voice