Vocal Fold Oscillations

In cooperation with Richard Wolf GmbH (Knittlingen) as well as the department for Phoniatry and Pedaudiology of the university hospital Erlangen, the Fraunhofer IIS developed a camera system which is now marketed by Richard Wolf GmbH.

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Capturing Movements in the Larynx and the Oscillations of the Vocal Folds with High Speed Cameras

Vocal Folds

Sitmmlippenanalyse Glottis
© Photo Fraunhofer IIS

Vocal Vold Oscillations, Glottis

During normal speaking, human vocal folds oscillate at 120 Hz (men), and 250 Hz (women). Since the visual perception system is not able to differentiate image sequences with more than 25 pictures per second, the need for a method able to record fast motions in the larynx and slow down them in play back for clinical examination of vocal fold oscillations exists.

For this purpose, a clinical usable highspeed camera system for the examination of vocal fold oscillations is being developed at Fraunhofer Institute for Integrated Circuits IIS, in cooperation with Richard Wolf GmbH (Knittlingen) and the department for phoniatrics and pedaudiology of the clinic of university Erlangen-Nuremberg. This system consists of a digital highspeed camera and a diagnosis software for knowledge based semiautomatic analysis of vocal fold oscillations.

Camera System for the Analysis of Vocal Fold Oscillations

Stimmlippenanalyse, Einzelbild
© Photo Fraunhofer IIS

Vocal Vold Oscillations, Single Image

The highspeed recording system consist of a camera head, a control system and an interface to a computer for combined control, archive and interpretation. The CMOS image sensor in the camera head has a spatial resolution of 256 x 256 pixel. The temporal resolution amount to 4000 images per second. The maximum duration of recording amount to two seconds in this system. A detachable 90° Magnifiying Laryngoscope from the company Wolf is adapted at the head of the camera for endoscopic views.

Interpretation

Stimmlippenanalyse, Kymo
© Photo Fraunhofer IIS

Vocal Fold Oscillations, Cymo

Beside pure inspecting of recorded and archived vocal fold oscillations in slow motion, two aspects are in the foreground for interpretation: The visualization and examination of the motion with digital kymograms, and the automatic analysis of motion and frequency of vocal fold oscillations. Both methods enable a reduction of recording data of about 90 percent. For digital kymograms image lines with identical parameters (x, y, a) are extracted in all single images of a sequence and combined to a strip image.

On a kymogram all motions of both vocal folds are catchable in one view. Especially divergences of symmetrie and periodicity of the oscillation are easy to recognize and usable for diagnosis of functional voice disorders. Beside to the visualization of vocal fold oscillations is the extraction of parameters of oscillations. With a semiautomatic method for motion analysis first of all motiongraphs (trajectories) are calculated. These trajectories are used to compute significant and objective parameters like the phoniatric base frequency, the phonation onset, the amplitude and the periodic time, for each vocal fold.

Further information

Brochure

Medical Image Processing

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