Modeling of Sound Transmission from Ear Canal to Cochlea

A 3-D finite element (FE) model of the human ear consisting of the external ear canal, middle ear, and cochlea is reported in this paper. The acoustic-structure-fluid coupled FE analysis was conducted on the model which included the air in the ear canal and middle ear cavity, the fluid in the cochlea, and the middle ear and cochlea structures (i.e., bones and soft tissues). The middle ear transfer function such as the movements of tympanic membrane, stapes footplate, and round window, the sound pressure gain across the middle ear, and the cochlear input impedance in response to sound stimulus applied in the ear canal were derived and compared with the published experimental measurements in human temporal bones. The frequency sensitivity of the basilar membrane motion and intracochlear pressure induced by sound pressure in the ear canal was predicted along the length of the basilar membrane from the basal turn to the apex. The satisfactory agreements between the model and experimental data in the literature indicate that the middle ear function was well simulated by the model and the simplified cochlea was able to correlate sound stimulus in the ear canal with vibration of the basilar membrane and pressure variation of the cochlear fluid. This study is the first step toward the development of a comprehensive FE model of the entire human ear for acoustic-mechanical analysis.     

人工听骨不同接入方式对耳结构动力响应的影响

目的 研究人工听骨接入方式对听力恢复的影响。方法 通过CT扫描技术,结合自编C＋＋程序读取CT数据中体单元建立人耳结构几何模型,将几何模型导入PATRAN中建立有限元数值模型。采用频率响应方法对耳结构模型进行流固耦合计算,同时分析人工听骨不同接入方式及接入位置对耳结构声音传导的影响。结果 通过对正常人耳的动力响应分析,得到数值模型中计算出的鼓膜凸与镫骨底板振幅与试验数据吻合,验证本文模型的正确性。结论接在鼓膜凸的位置其动力响应最好,镫骨振幅高于其他连接方式。即人工听骨接在鼓膜凸的位置比较吻合人耳的生理功能,其重建听力效果更好。     

人耳鼓膜病变数值分析

目的研究鼓膜厚度和硬度对人耳传声的影响。方法利用CT获取志愿者耳部结构临床资料,使用Matlab软件提取相关结构的边界,将边界文件导入ANSYS建立人耳结构数值有限元模型。结果利用本文人耳数值模型,在外耳道口施加105dB声压,进行200～8000Hz频率范围的谐响应分析。以此研究在鼓膜病变情况下,鼓膜和镫骨底板位移幅值的变化规律。结论用数值方法解释了鼓膜病变对传声的影响,为鼓膜修补提供了力学参考。     

正常人高分辨率CT中耳三维有限元建模方法

目的探索根据正常人颞骨高分辨率CT二维图像建立中耳三维有限元实体模型的方法。方法获得无中耳传音结构病变志愿者高分辨颞骨CT资料,使用Photoshop、Amira、HyperMesh及Abaqus软件根据二维CT图像建立中耳三维有限元实体模型。结果建立了包含鼓膜、听骨链的中耳三维有限元实体模型,模型几何尺寸在正常解剖数据范围内。结论探索出一种基于正常人颞骨高分辨率CT二维图像的中耳三维有限元实体建模方法,具有快捷、方便、廉价、无创性的优点,为进一步进行中耳声音传导机制有限元分析奠定了基础。     

Acoustic-structural coupled finite element analysis for sound transmission in human ear--pressure distributions

A three-dimensional (3D) finite element (FE) model of human ear with accurate structural geometry of the external ear canal, tympanic membrane (TM), ossicles, middle ear suspensory ligaments, and middle ear cavity has been recently reported by our group. In present study, this 3D FE model was modified to include acoustic-structural interfaces for coupled analysis from the ear canal through the TM to middle ear cavity. Pressure distributions in the canal and middle ear cavity at different frequencies were computed under input sound pressure applied at different locations in the canal. The spectral distributions of middle ear pressure at the oval window, round window, and medial site of the umbo were calculated and the results demonstrated that there was no significant difference of pressures between those locations at frequency below 3.5 kHz. Finally, the influence of TM perforation on pressure distributions in the canal and middle ear cavity was investigated for perforations in the inferior-posterior and inferior sites of the TM in the FE model and human temporal bones. The results show that variation of middle ear pressure is related to the perforation type and location, and is sensitive to frequency.     

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

The anterior tympanomeatal angle (ATA) blunting is clinically defined as a certain degree of the ATA obliteration due to excessive fibrous tissue formation, which is a relatively common complication of external auditory canal (EAC) related operations. The aim of this study was to examine the effect of ATA blunting on the middle ear transfer function using a finite element (FE) model. Results showed that the displacements at the tympanic membrane (TM), at the manubrium and at the stapes footplate, and also the ratio of stapes footplate velocity to the sound pressure in the EAC were decreased to various degrees from ATA blunting of Grades 1–4. This was more significant with TM thickening at the frequencies below 3.2 kHz, particularly in Grades 3 and 4 when analyzing the anterior region of the TM. The phase differences of TM and stapes footplate increased with the ATA blunting from Grades 1 to 4 in relation to normal ATA. It is noteworthy that the vibration mode of the malleus does not show obvious change, compared to the displacement reduction at the TM with ATA blunting Grades 1–4. These results suggest that FE analysis of ATA blunting effect appears to be effective.     

高压下中耳结构动力损伤研究

目的研究高压对中耳结构造成的损伤。方法基于CT扫描建立中耳结构有限元数值模型,对模型施加随时间变化的压力,分析鼓膜以及镫骨足板的应力、应变和位移变化。结果获得的计算结果与相关文献中的试验数据吻合,验证了所建中耳模型的准确性。高压会对中耳造成损伤,随着压力的增加,损伤加重;快速加压使得中耳损伤严重,对内耳的影响较小;慢速加压也能导致中耳损伤,但在中耳损伤前,内耳会损伤。结论高压容易导致人耳出现损伤,为避免听力受到影响,在加压过程中要控制好加压速率。     

Micro-CT of the human ossicular chain: Statistical shape modeling and implications for otologic surgery

The ossicular chain is a middle ear structure consisting of the small incus, malleus and stapes bones, which transmit tympanic membrane vibrations caused by sound to the inner ear. Despite being shown to be highly variable in shape, there are very few morphological studies of the ossicles. The objective of this study was to use a large sample of cadaveric ossicles to create a set of three-dimensional models and study their statistical variance. Thirty-three cadaveric temporal bone samples were scanned using micro-computed tomography (μCT) and segmented. Statistical shape models (SSMs) were then made for each ossicle to demonstrate the divergence of morphological features. Results revealed that ossicles were most likely to vary in overall size, but that more specific feature variability was found at the manubrium of the malleus, the long process and lenticular process of the incus, and the crura and footplate of the stapes. By analyzing samples as whole ossicular chains, it was revealed that when fixed at the malleus, changes along the chain resulted in a wide variety of final stapes positions. This is the first known study to create high-quality, three-dimensional SSMs of the human ossicles. This information can be used to guide otological surgical training and planning, inform ossicular prosthesis development, and assist with other ossicular studies and applications by improving automated segmentation algorithms. All models have been made publicly available.     

A micro-drive hearing aid: a novel non-invasive hearing prosthesis actuator

The direct hearing device (DHD) is a new auditory prosthesis that combines conventional hearing aid and middle ear implant technologies into a single device. The DHD is located deep in the ear canal and recreates sounds with mechanical movements of the tympanic membrane. A critical component of the DHD is the microactuator, which must be capable of moving the tympanic membrane at frequencies and magnitudes appropriate for normal hearing, with little distortion. The DHD actuator reported here utilized a voice coil actuator design and was 3.7 mm in diameter. The device has a smoothly varying frequency response and produces a precisely controllable force. The total harmonic distortion between 425 Hz and 10 kHz is below 0.5 % and acoustic noise generation is minimal. The device was tested as a tympanic membrane driver on cadaveric temporal bones where the device was coupled to the umbo of the tympanic membrane. The DHD successfully recreated ossicular chain movements across the frequencies of human hearing while demonstrating controllable magnitude. Moreover, the micro-actuator was validated in a short-term human clinical performance study where sound matching and complex audio waveforms were evaluated by a healthy subject.     

置换部分听骨赝复物后对人耳听力恢复的影响

目的探讨听骨部分置换术中不同的置换方式对患者术后听力的影响。方法根据人体正常右耳CT扫描结果,用自编程序将CT扫描数值化并导入PATRAN重建人耳三维有限元模型,对其进行声音传导动力分析,并与试验数据对比。结果通过正常人耳结构动力响应分析结果与实验数据吻合,验证了模型的正确性;在0.1～10 kHz频率下保留部分锤骨柄置换人工听骨比不保留锤骨柄术后听力恢复更好,听力恢复值在11.56～28.91 dB之间;保留部分锤骨柄时鼓膜处的最大应力值比不保留锤骨柄时更小;厚2.0 mm软骨片在0.1～0.6 kHz,2～10 kHz频率上听力恢复较好;厚0.1 mm软骨片在0.6～2 kHz频率上听力恢复较好。结论在听骨部分置换术中,保留部分锤骨柄比不保留锤骨柄听力恢复效果更好;鼓膜与人工听骨的接触面上垫置的软骨片厚度在0.1～2.0 mm之间对人耳听力恢复效果较好。     

不同激振位置对压电式人工中耳听力补偿性能的影响

研究不同激振位置对压电式人工中耳听力补偿性能的影响,确定压电式人工中耳最优激振位置。建立人耳有限元模型,并通过和相关实验数据进行对比验证模型的可靠性。基于该模型,分别在鼓膜脐部、砧骨体、砧骨长突和圆窗施加相同的位移驱动,通过检测镫骨足底板位移及基底膜的最大位移,分析这些位置的激振对人工中耳听力补偿性能的影响。结果表明,以镫骨足底板位移为评估标准会低估圆窗激振的高频听力补偿效果。砧骨长突激振下的基底膜特征位置处的运动位移大于激振鼓膜脐部及激振砧骨体时的位移值,其中激振砧骨体时的基底膜特征位置处运动位移最小;激振圆窗时的基底膜特征位置处运动位移在低频段小于激振其他位置时对应的位移值,但在中、高频段其激振效果最好。在频率低于400 Hz时,砧骨长突激励听力补偿效果最好,圆窗激励听力补偿效果最差。当频率大于1 kHz时,圆窗激励听力补偿效果比其他位置好。以传统的镫骨足底板响应为评估标准,将低估圆窗激振式人工中耳的听力补偿效果。     

Morphometry of auditory ossicles in medieval human remains from Central Europe

Human auditory ossicles, the malleus, the incus, and the stapes, are located in the tympanic cavity in the temporal bone and through forming a chain for the sound transmission from the tympanic membrane to the cochlea, they play an important role in the hearing process. Despite their clinical, phylogenetic, and evolutionary significance, the morphometry of the human ear bones has not been examined systematically. The ear ossicles are the smallest bones of the human skeleton, attaining their final size and morphology already at birth. Initially, they have been found to exhibit minimal morphometric variation, but further studies brought the opposite results. The aim of this study was to examine the morphometric variation of human auditory ossicles recovered from medieval and postmedieval subadult skeletons from Poland, Central Europe. The analysis involved in a total of 166 ear bones. Their measurements were performed on microscopic images using CorelDraw x4, according to a protocol of Quam and Rak with modification of Flohr et al. and Wadhwa et al. Our study showed a significant metric variation in the measurements taken at areas of the greatest morphological variability of the ossicles. We found that greater linear dimensions were associated with lower values of angular measurements. These results reveal the inherent variation found in these supposed functionally constrained structures. Representation of even greater number of populations, time periods, and developmental stages are needed. Further study will expand our understanding of the global scope of variation found in ear ossicular morphology and its functional implications for paleoanthropology.     

中耳病变及人工镫骨形体研究

目的 研究听骨韧带、肌腱硬化和切除以及人工镫骨置换对声音传导的影响。方法 基于CT扫描数据,通过自编C＋＋程序读取CT数据中体单元建立人耳结构几何模型,将几何模型导入PATRAN中赋予材料参数、设置关节接触面以及相应其他边界条件生成数值模型。结果 利用本文人耳数值模型进行正常耳和病变耳的谐响应分析,得到正常耳和病变耳镫骨底板和鼓膜凸的振幅变化规律。并由此构建了套型人工镫骨。结论 正常耳的模拟结果与实验测试结果吻合,证明了本模型准确性,可以模拟人传声功能。本模型模拟病变耳的计算结果可以从力学角度解释病变对声音传导的影响,为病变耳治疗提供参考。本文的套型人工镫骨较我国临床用的环型人工镫骨更吻合人耳的生理功能,其重建听力效果更好。     

外耳道静压对声音传递和耳蜗输入影响数值分析

为分析静压变化对中耳听骨链运动和耳蜗输入的影响,运用有限元模型研究外耳道静压导致的中耳声音传递功能和耳蜗激励输入改变。首先,根据相关实验测量数据并结合有限元分析,拟合了耳道静压力与中耳各构件有效弹性模量关系的经验公式;然后,通过材料参数的改变模拟压力造成的中耳结构刚度增加,分析耳道静压对中耳机动性的影响和不同耳道压力下镫骨底板位移、速度和耳蜗两窗压力差的变化。计算结果与相关的文献实验数据有较好的符合,说明所建立的计算模型在模拟静压条件下中耳传递功能方面的合理性。结果表明在低频范围(0～0.6 kHz)外耳道静压对两窗压力差的影响稍大于对镫骨位移的影响。     

Finite element analysis of the effects of a floating mass transducer on the performance of a middle ear implant

Experimental evidence has shown that floating mass transducers (FMTs) play a key role in the performance of middle ear implants. However, because of the tiny size and complex structure of the middle ear, systematic experimental study of the influences of FMTs is difficult to carry out. In this paper we develop a FMT-attached middle-ear finite element model to investigate some effects of a FMT on the performance of a middle ear implant. This model was constructed based on a complete set of computerized tomography section images of a healthy volunteer's left ear. The validity of the developed model was verified by comparing the model-predicted motion of the tympanic membrane and stapes footplate with published experimental data. The result shows that the FMT produces a mass loading effect prominently at high frequencies, the force required to drive the incus to the equivalent of 100 dB sound pressure level (SPL) is about 89?μN, and setting the attachment position of the FMT close to the incudostapedial joint can enhance the driving effect.     

细菌生物膜对置换钛质听骨赝复物听力恢复的影响

目的 探讨生物膜不同成长时期对部分钛质听骨赝复物结构动力行为的影响,为临床治疗分泌性中耳炎等疾病提供理论依据。方法 基于人体正常右耳的CT扫描图像,结合自编程序,重建人耳三维有限元模型,对其进行声音传导动力分析,并与实验数据对比。采用频率响应方法对耳结构模型进行计算,同时分析不同生长时期的细菌生物膜生长在人工钛质听骨上对声音传导的影响。结果 模拟得到鼓膜凸和镫骨底板振幅与实验数据吻合,验证了模型的正确性。生物膜的存在会使患者听力在低频段有0~1.6 dB的损伤;生物膜沿部分听骨赝复物径向生长会使患者听力在中高频阶段有0~12 dB的损伤,尤其是在8 kHz时,听力损伤高达11.2 dB。结论 细菌生物膜对患者听力有影响,在低频段会使患者听力损失,在高频段听力有增加。细菌生物膜在人工听骨上的径向生长会降低听力,影响人工假体对听力恢复正常的工效。     

Mechanical properties of stapedial annular ligament

Stapedial annular ligament (SAL) provides a sealed but mobile boundary between the stapes footplate and oval window bony wall. Mechanical properties of the SAL affect the transmission of ossicular movement into the cochlea in sound conduction. However, the mechanical properties of this tissue have never been investigated due to its complexity. In this paper, we report measurement of the viscoelastic properties of SAL on human cadaver temporal bones using a micro-material testing system with digital image correlation analysis. The measured load-deformation relations of SAL samples were converted into shear stress-shear strain relationship, stress relaxation function, and ultimate shear stress and shear strain of the SAL. The hyperelastic Ogden model was used to describe constitutive behavior of the SAL and a 3D finite element model of the experimental setup with SAL was created for assessing the effects of loading variation and measurement errors on results. The study demonstrates that the human SAL is a typical viscoelastic material with hysteresis, nonlinear stress-strain relationship and stress relaxation function. The shear modulus changes from 3.6 to 220 kPa when the shear stress increases from 2 to 140 kPa. These results provide useful information on quasi-static behavior of the SAL.     

Measurement of the vibration of the middle ear ossicles with removed eardrum: A method for quantification of ossicular fixation

Chronic inflammation of the middle ear is a common disease in which the mobility of the middle ear ossicles may be reduced; resulting in hearing impairment. Knowledge of the degree of ossicular mobility is useful in helping a surgeon determine how to proceed with treatment. In advanced cases, mobility can be assessed by manually pressing on the ossicles, but in less advanced cases manual assessment can provide limited useful information. Ossicular vibration can be measured with a laser vibrometer, but only the manubrium of the malleus is optically visible without removing the eardrum. Since the eardrum is the means by which acoustic energy is translated into the mechanical motion of the ossicles, removing it renders any subsequent measurements of ossicular motion meaningless. We therefore devised a technique in which the ossicles are vibrated magnetically. After measuring the response of the umbo to acoustic stimulation, we removed the eardrum and attached a small magnet to the manubrium. An electromagnetic excitation coil was then used to vibrate the magnet, and the signal to the coil was adjusted until the vibration of the ossicles matches that achieved acoustically. In this paper we explain the method and describe some test measurements on a vinyl membrane, and some preliminary results obtained on a fresh-frozen human temporal bone before and after artificial fixation of the ossicles.     

中耳畸形对圆窗激振听力补偿性能影响的数值分析

目的研究中耳畸形对圆窗激振性能的影响,为圆窗激振式人工中耳的优化提供理论支持。方法构建包含两腔不对称的非螺旋耳蜗的人耳有限元模型,并与实验数据进行对比,验证模型的可靠性。基于该模型,通过改变相应组织的材料属性,分别模拟听骨链固定、听骨链融合、听小骨缺损3种中耳畸形对圆窗激振性能的影响。结果中耳畸形主要影响圆窗激振式人工中耳的低频性能,听骨链固定和听骨链融合对圆窗激振起恶化效果。镫骨固定对圆窗激振补偿性能的影响最大,恶化量高达47.93 dB;听小骨缺损可提高圆窗激振的性能,最大改善量为6.24 dB。结论中耳畸形对圆窗激振的低频性能有影响,临床植入圆窗激振式人工中耳时需要针对性地提高其作动器的输出量。