Technical information
The traditional photoelectric glottograph (PGG) is invasive: a fiberscope has to be inserted through one nostril and passed into the supraglottal cavity in order to estimate the area between the vocal folds during continuous speech. A new non-invasive technique, the ePGG, has been developed and patented at the LPP. It uses an external LED light source that illuminates the larynx from the outside, making this a non-invasive approach.
When the glottis is open, the light passes through it and is detected at the level of the trachea by a photosensor. Technical challenges include having transillumination that is sufficiently strong through tissue, and detection of an ultra-low frequency signal. This instrument enables the phonetician or clinician to observe glottal movement during continuous speech, giving it both phonetic and clinical applications and enabling measurement of changes in glottal area.