In Vivo Measurement of Ear Ossicle and Bony Wall Vibration by Sound Stimulation of Cartilage Conduction.

The cartilage-conduction pathway was recently proposed as a third auditory pathway; however, middle-ear vibrations have not yet been investigated in vivo. We aimed to measure the ossicles and bone vibration upon cartilage-conduction stimulation with a non-contact laser Doppler vibrometer. We recruited adult patients with normal ear structures who underwent cochlear implant surgery at our hospital between April 2020 and December 2022. For sound input, a cartilage-conduction transducer, custom-made by RION Corporation (Tokyo, Japan), was fixed to the surface of the tragus and connected to an audiometer to regulate the output. A posterior tympanotomy was performed and a laser beam was directed through the cavity to measure the vibration of the ossicles, cochlear promontory, and posterior wall of the external auditory canal. Five participants (three men, mean age: 56.4 years) were included. The mean hearing loss on the operative side was 96.3 dB HL in one patient, and that of the other patients was off-scale. The vibrations were measured at a sound input of 1 kHz and 60 dB. We observed vibrations of all three structures, demonstrating the existence of cartilage-conduction pathways in vivo. These results may help uncover the mechanisms of the cartilage-conduction pathway in the future.

Sequential motion of the ossicular chain measured by laser Doppler vibrometry.

OBJECTIVE: In order to help a surgeon make the best decision, a more objective method of measuring ossicular motion is required. METHODS: A laser Doppler vibrometer was mounted on a surgical microscope. To measure ossicular chain vibrations, eight patients with cochlear implants were investigated. To assess the motions of the ossicular chain, velocities at five points were measured with tonal stimuli of 1 and 3 kHz, which yielded reproducible results. The sequential amplitude change at each point was calculated with phase shifting from the tonal stimulus. Motion of the ossicular chain was visualized from the averaged results using the graphics application. RESULTS: The head of the malleus and the body of the incus showed synchronized movement as one unit. In contrast, the stapes (incudostapedial joint and posterior crus) moved synchronously in opposite phase to the malleus and incus. The amplitudes at 1 kHz were almost twice those at 3 kHz. CONCLUSIONS: Our results show that the malleus and incus unit and the stapes move with a phase difference.

Analysis of Direct Simultaneous Measurement of Glottal Airflow Velocity, Subglottal Pressure, and High-Speed Imaging Using Flexible Transnasal Endoscope in a Human Subject.

It is difficult to directly observe glottal airflow velocity just above the glottis due to sensor size requirements and limited accessibility. We developed a miniature hot-wire probe and flexible fiberscopic high-speed imaging system for human examinations. Simultaneous direct measurement of glottal airflow velocity, subglottal pressure, and vocal fold vibration was achieved in a patient who was treated with a T-tube for tracheal stenosis. Airflow velocity changes at the anterior midline of the vocal folds were synchronized with subglottal pressure changes during each phonation cycle. The velocity at the anterior midline of the vocal folds showed a rhythmic pattern of sharp, high peaks. The result of fast Fourier transform analysis indicated that glottal velocity at the anterior midline of the vocal folds had abundant high-frequency components that were not affected by resonance of the vocal tract. Airflow velocity was variable and diminished except at the anterior midline of the vocal folds.

Sequential multipoint motion of the tympanic membrane measured by laser Doppler vibrometry: preliminary results for normal tympanic membrane.

BACKGROUND: Numerous studies have reported sound-induced motion of the tympanic membrane (TM). To demonstrate sequential motion characteristics of the entire TM by noncontact laser Doppler vibrometry (LDV), we have investigated multipoint TM measurement. MATERIALS AND METHODS: A laser Doppler vibrometer was mounted on a surgical microscope. The velocity was measured at 33 points on the TM using noncontact LDV without any reflectors. Measurements were performed with tonal stimuli of 1, 3, and 6 kHz. Amplitudes were calculated from these measurements, and time-dependent changes in TM motion were described using a graphics application. RESULTS: TM motions were detected more clearly and stably at 1 and 3 kHz than at other frequencies. This is because the external auditory canal acted as a resonant tube near 3 kHz. TM motion displayed 1 peak at 1 kHz and 2 peaks at 3 kHz. Large amplitudes were detected in the posterosuperior quadrant (PSQ) at 1 kHz and in the PSQ and anteroinferior quadrant (AIQ) at 3 kHz. The entire TM showed synchronized movement centered on the PSQ at 1 kHz, with phase-shifting between PSQ and AIQ movement at 3 kHz. Amplitude was smaller at the umbo than at other parts. In contrast, amplitudes at high frequencies were too small and complicated to detect any obvious peaks. CONCLUSION: Sequential multipoint motion of the tympanic membrane showed that vibration characteristics of the TM differ according to the part and frequency.

Analysis of human glottal velocity using hot-wire anemometry and high-speed imaging.

OBJECTIVES: The aim of this study was to analyze glottal velocity and glottal opening and closure. For this purpose, we developed a miniature, flexible, hot-wire probe that can make truly instantaneous measurements of the human larynx in vivo. METHODS: A miniature hot-wire tip was inserted into a flexible transnasal endoscope. Fiberscopic examination was performed transnasally so that we could observe glottal vibration using high-speed imaging. The tip of the hot-wire probe was placed just above the glottis. The position of the probe was carefully monitored and checked with another flexible endoscope. RESULTS: Changes in velocity were recorded periodically. The velocity was higher in close proximity to the vocal folds. High-speed motion pictures were taken at a rate of 2000 frames per second with an auxiliary light source. CONCLUSIONS: Quantitative analysis of glottal velocity is required to improve our understanding of the relationship between laryngeal physiology and acoustics in humans. To solve the problem of synchronization inaccuracy, glottal velocity was captured instantaneously in the high-speed imaging system's processor memory.