What is it about?
Mouth-to-microphone (MTM) distance is important when measuring the sound of voice. However, determining the MTM distance for laryngoscope-mounted microphones during laryngoscopic examinations done by laryngologists and voice pathologists is cumbersome. We introduce a novel solution for such cases, using the depth of insertion of the laryngoscope into the mouth DI as a reference distance. We measured the average insertion depth, DI, in 60 adult women and 60 adult men for rigid laryngoscopes with 70° and 90° view. We found the DI for the 70°/90° laryngoscope to be 9.7 ± 0.9/9.4 ± 0.6 cm in men, 8.9 ± 0.9/8.7 ± 0.7 cm in women, and 9.3 ± 0.9/9.0 ± 0.7 cm in all adults. Using these values, we show that, for microphones fixed at 15–40 cm from the tip of the laryngoscope, the final MTM distances are between 5 and 35 cm from the lips, and the standard uncertainties of these distances are between 16% and 2.5%. Our solution allows laryngologists and laryngoscope manufacturers to set and estimate the MTM distance for any rigid laryngeal endoscope with a microphone attached with reasonable accuracy, avoiding the need to measure this distance in vivo in routine practice. The full article is freely available here: https://doi.org/10.3390/jcm12247560
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Photo by Panos Sakalakis on Unsplash
Why is it important?
When doing laryngeal examinations of voice, the video of the laryngeal exam should be stored together with the sound of voice. For capturing the sound, it is convenient to fix a miniature microphone directly to the laryngeal endoscope. We describe a method how to determine the distance of such a microhone from the mouth. Since the sound of voice changes with the distance from the mouth, this information is important to improve the reproducibility and interpretability of voice examinations.
Perspectives
When we got a new rigid laryngeal endoscope with an integrated microphone, our laryngologists and voice pathologists found it comfortable and practical, but I started to wonder: At what distance does such a microphone capture the voice during laryngoscopy? Our video-laryngeal stroboscope system showed to us the decibels of the SPL of voice, but these values do not have much meaning when the distance from the mouth is unknown. Therefore, we started investigating it with my student Dominika Valaskova. To find the microphone distance from the mouth, we needed first to find out how deep is a rigid endoscope inserted into the mouth. Our measurements show that this depth is 9.3 ± 0.9/9.0 ± 0.7 cm in adult subjects for 70° / 90° rigid endoscopes. When this depth is subtracted from the microphone position on the laryngoscope, it reveals the mouth-to-microphone distance (see the paper for details). Interestingly, the variability of the endoscope insertion depth among adults is not very large, so the mouth-to-microphone distance can be found with reasonable uncertainty. Our findings can also be used to find a proper position for the attachment of the microphone to the laryngoscope so that the microphone ends up at a standard unified distance. Since laryngeal behavior changes with voice intensity, we hope our findings will help achieving better reproducibility of results from laryngeal examinations across different institutes around the world. The full article is freely available here: https://doi.org/10.3390/jcm12247560
Dr. Jan G. Svec
Univerzita Palackeho v Olomouci
Read the Original
This page is a summary of: Determining the Mouth-to-Microphone Distance in Rigid Laryngoscopy: A Simple Solution Based on the Newly Measured Values of the Depth of Endoscope Insertion into the Mouth, Journal of Clinical Medicine, December 2023, MDPI AG,
DOI: 10.3390/jcm12247560.
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