Effect of anterior tympanomeatal angle blunting on the middle ear transfer function using a finite element ear model

Characterization of middle ear soft tissue damping and its role in sound transmission

Damping plays an important role in the middle ear (ME) sound transmission system. However, how to mechanically characterize the damping of ME soft tissues and the role of damping in ME sound transmission have not yet reached a consensus. In this paper, a finite element (FE) model of the partial external and ME of the human ear, considering both Rayleigh damping and viscoelastic damping for different soft tissues, is developed to quantitatively investigate the damping in soft tissues effects on the wide-frequency response of the ME sound transmission system. The model-derived results can capture the high-frequency (above 2 kHz) fluctuations and obtain the 0.9 kHz resonant frequency (RF) of the stapes velocity transfer function (SVTF) response. The results show that the damping of pars tensa (PT), stapedial annular ligament (SAL) and incudostapedial joints (ISJ) can help smooth the broadband response of the umbo and stapes footplate (SFP). It is found that, between 1 and 8 kHz, the damping of the PT increases the magnitude and phase delay of the SVTF above 2 kHz while the damping of the ISJ can avoid excessive phase delay of the SVTF, which is important in maintaining the synchronization in high-frequency vibration but has not been revealed before. Below 1 kHz, the damping of the SAL plays a more important role, and it can decrease the magnitude but increases the phase delay of the SVTF. This study has implications for a better understanding of the mechanism of ME sound transmission.

High-Frequency Conductive Hearing following Total Drum Replacement Tympanoplasty

OBJECTIVES

Conventional reporting of posttympanoplasty hearing outcomes use a pure-tone averaged air-bone gap (ABG) largely representing a low-frequency sound conduction. Few studies report high-frequency conductive hearing outcomes. Herein, we evaluate high-frequency ABG in patients following temporalis fascia total drum replacement.

STUDY DESIGN

Case series with chart review.

SETTING

Tertiary care center.

SUBJECTS AND METHODS

All patients who underwent type 1 tympanoplasty using a lateral graft total drum replacement technique between August 2016 and February 2019 were identified. Patients with pre- and postoperative audiograms were included. Low-frequency ABG was calculated as the mean ABG at 250, 500, and 1000 Hz. High-frequency ABG was calculated at 4 KHz. Pre- and postoperative ABGs were compared.

RESULTS

Twenty-three patients were included, and the mean age at surgery was 44 years (range, 9-68 years). Perforation etiology was from trauma (n = 14) or chronic otitis media (n = 9). Preoperative mean low-frequency ABG was 27.8 ± 12.6 dB and mean high-frequency ABG was 21.5 ± 15.1 dB (P = .044). Postoperatively, the mean low-frequency ABG was significantly reduced by 15.5 ± 13.3 dB (P < .001) while the mean high-frequency ABG insignificantly changed (reduced by 2.6 ± 16.2 dB, P = .450).

CONCLUSION

In a series of patients undergoing temporalis fascia total drum replacement, low-frequency ABG improved; however, high-frequency conductive hearing loss persists. Conventional methods of reporting ABG may not identify persistent high-frequency ABG. These results merit further study across a range of tympanoplasty graft materials and surgical techniques.

Transient response of the human ear to impulsive stimuli: A finite element analysis

Nowadays, the steady-state responses of human ear to pure tone stimuli have been widely studied. However, the temporal responses to transient stimuli have not been investigated systematically to date. In this study, a comprehensive finite element (FE) model of the human ear is used to investigate the transient characteristics of the human ear in response to impulsive stimuli. There are two types of idealized impulses applied in the FE analysis: the square wave impulse (a single positive pressure waveform) and the A-duration wave impulse (both of positive and negative pressure waveforms). The time-domain responses such as the displacements of the tympanic membrane (TM), the stapes footplate (SF), the basilar membrane (BM), the TM stress distribution, and the cochlea input pressure are derived. The results demonstrate that the TM motion has the characteristic of spatial differences, and the umbo displacement is smaller than other locations. The cochlea input pressure response is synchronized with the SF acceleration response while the SF displacement response appears with some time delay. The BM displacement envelope is relatively higher in the middle cochlea and every portion of BM vibrates at its best frequency approximately. The present results provide a good understanding of the transient response of the human ear.