Abstract
Laryngo-stroboscopy is a common clinical tool used to observe vocal fold oscillation, yet it is not appropriate for visualizing the oscillations that contain sub-harmonic waves that often appear in pathological vocal folds. Here, we propose a novel technique based on stroboscopy in which such pathological vocal fold oscillations can be observed by applying FFT (fast Fourier transformation) analysis. We tested two algorithms to determine the stroboscopic illumination frequency : Illuminations on the basis of (i) beat frequency and (ii) multi-light sources. A vocal fold oscillation model with two different fundamental frequencies mimicking pathological conditions such as nodular vocal folds was used to evaluate the performance of the algorithms. The beat frequency was extracted from the sound wave by FFT analysis and used to stroboscopically illuminate the oscillations, demonstrating that the algorithm is useful for observing pathological oscillations, but may be inapplicable to clinical cases because of its low light intensity. In contrast, the alternative algorithm using multi-light sources to illuminate each fundamental oscillation simultaneously showed good performance visualizing the pathological oscillations as well as in the level of clarity, demonstrating that the newly designed laryngo-stroboscopy system is valuable for observing pathological vocal fold oscillations.
