Sequential Multipoint Motion of the Tympanic Membrane Measured by Laser Doppler Vibrometry: Preliminary Results for Normal Tympanic Membrane.

Otology & Neurotology

PubMedID: 24317215

Kunimoto Y, Hasegawa K, Arii S, Kataoka H, Yazama H, Kuya J, Kitano H. Sequential Multipoint Motion of the Tympanic Membrane Measured by Laser Doppler Vibrometry: Preliminary Results for Normal Tympanic Membrane. Otol Neurotol. 2014;35(4):719-24.
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.