Reverse Transmission along the Ossicular Chain in Gerbil

In a healthy cochlea stimulated with two tones f (1) and f (2), combination tones are generated by the cochlea's active process and its associated nonlinearity. These distortion tones travel "in reverse" through the middle ear. They can be detected with a sensitive microphone in the ear canal (EC) and are known as distortion product otoacoustic emissions. Comparisons of ossicular velocity and EC pressure responses at distortion product frequencies allowed us to evaluate the middle ear transmission in the reverse direction along the ossicular chain. In the current study, the gerbil ear was stimulated with two equal-intensity tones with fixed f (2)/f (1) ratio of 1.05 or 1.25. The middle ear ossicles were accessed through an opening of the pars flaccida, and their motion was measured in the direction in line with the stapes piston-like motion using a laser interferometer. When referencing the ossicular motion to EC pressure, an additional amplitude loss was found in reverse transmission compared to the gain in forward transmission, similar to previous findings relating intracochlear and EC pressure. In contrast, sound transmission along the ossicular chain was quite similar in forward and reverse directions. The difference in middle ear transmission in forward and reverse directions is most likely due to the different load impedances-the cochlea in forward transmission and the EC in reverse transmission.     

Conductive Hearing Loss Induced by Experimental Middle-Ear Effusion in a Chinchilla Model Reveals Impaired Tympanic Membrane-Coupled Ossicular Chain Movement

Otitis media with effusion (OME) occurs when fluid collects in the middle-ear space behind the tympanic membrane (TM). As a result of this effusion, sounds can become attenuated by as much as 30–40 dB, causing a conductive hearing loss (CHL). However, the exact mechanical cause of the hearing loss remains unclear. Possible causes can include altered compliance of the TM, inefficient movement of the ossicular chain, decreased compliance of the oval window-stapes footplate complex, or altered input to the oval and round window due to conduction of sound energy through middle-ear fluid. Here, we studied the contribution of TM motion and umbo velocity to a CHL caused by middle-ear effusion. Using the chinchilla as an animal model, umbo velocity (V _U) and cochlear microphonic (CM) responses were measured simultaneously using sinusoidal tone pip stimuli (125 Hz–12 kHz) before and after filling the middle ear with different volumes (0.5–2.0 mL) of silicone oil (viscosity, 3.5 Poise). Concurrent increases in CM thresholds and decreases in umbo velocity were noted after the middle ear was filled with 1.0 mL or more of fluid. Across animals, completely filling the middle ear with fluid caused 20–40-dB increases in CM thresholds and 15–35-dB attenuations in umbo velocity. Clinic-standard 226-Hz tympanometry was insensitive to fluid-associated changes in CM thresholds until virtually the entire middle-ear cavity had been filled (approximately >1.5 mL). The changes in umbo velocity, CM thresholds, and tympanometry due to experimentally induced OME suggest CHL arises primarily as a result of impaired TM mobility and TM-coupled umbo motion plus additional mechanisms within the middle ear.     

The Effect of Ear Canal Orientation on Tympanic Membrane Motion and the Sound Field Near the Tympanic Membrane

The contribution of human ear canal orientation to tympanic membrane (TM) surface motion and sound pressure distribution near the TM surface is investigated by using an artificial ear canal (aEC) similar in dimensions to the natural human ear canal. The aEC replaced the bony ear canal of cadaveric human temporal bones. The radial orientation of the aEC relative to the manubrium of the TM was varied. Tones of 0.2 to 18.4 kHz delivered through the aEC induced surface motions of the TM that were quantified using stroboscopic holography; the distribution of sound in the plane of the tympanic ring P_TR was measured with a probe tube microphone. The results suggest that the ear canal orientation has no substantial effect on TM surface motions, but P_TR at frequencies above 10 kHz is influenced by the ear canal orientation. The complex TM surface motion patterns observed at frequencies above a few kilohertz are not correlated with simpler variations in P_TR distribution at the same frequencies, suggesting that the complex sound-induced TM motions are more related to the TM mechanical properties, shape, and boundary conditions rather than to spatial variations in the acoustic stimulus.     

Nonlinear Vibration Response Measured at Umbo and Stapes in the Rabbit Middle ear

Using laser vibrometry and a stimulation and signal analysis method based on multisines, we have measured the response and the nonlinearities in the vibration of the rabbit middle ear at the level of the umbo and the stapes. With our method, we were able to detect and quantify nonlinearities starting at sound pressure levels of 93-dB SPL. The current results show that no significant additional nonlinearity is generated as the vibration signal is passed through the middle ear chain. Nonlinearities are most prominent in the lower frequencies (125 Hz to 1 kHz), where their level is about 40 dB below the vibration response. The level of nonlinearities rises with a factor of nearly 2 as a function of sound pressure level, indicating that they may become important at very high sound pressure levels such as those used in high-power hearing aids.     

Fixation and detachment of superior and anterior malleolar ligaments in human middle ear: experiment and modeling

The aim of this study is to investigate the function of the superior malleolar ligament (SML) and the anterior malleolar ligament (AML) in human middle ear for sound transmission through simulations of fixation and detachment of these ligaments in human temporal bones and a finite element (FE) ear model. Two laser vibrometers were used to measure the vibrations of the tympanic membrane (TM) and stapes footplate. A 3-D FE ear model was used to predict the transfer function of the middle ear with ligament fixation and detachment. The results demonstrate that fixations and detachments of the SML and AML had different effects on TM and stapes footplate movements. Fixation of the SML resulted in a reduction of displacement of the TM (umbo) and the footplate at low frequencies (f < 1000 Hz), but also caused a shift of displacement peak to higher frequencies. Fixation of both SML and AML caused a reduction of 15 dB at umbo or stapes at low frequencies. Detachment of the SML had almost no effect on TM and footplate mobility, but AML detachment had a minor effect on TM and footplate movement. The FE model was able to predict the effects of SML and AML fixation and detachment.     

Optimal graft thickness for different sizes of tympanic membrane perforation in cartilage myringoplasty: a finite element analysis

OBJECTIVE: The purpose of this study was to determine, using finite element analysis, the optimal graft thickness for cartilage myringoplasty in patients with different sizes of tympanic membrane (TM) perforations. STUDY DESIGN: We developed a cartilage plate-TM-coupled model using high-resolution computed tomography and finite element analysis. The geometric models of the perforated TM were generated using Patran and ANSYS software. METHOD: Three different sizes of TM perforations (15%, 55%, and 85%, representing small, medium, and large perforations, respectively) were created in the pars tensa. A cartilage plate was used to repair the eardrum perforation, and the new TM-cartilage coupled complex was loaded into our three-dimensional biomechanical model for analysis. The frequency-amplitude responses for different cartilage thicknesses were compared with those for natural TM. RESULTS: Our results show that, first, in cases with 85% perforation, the frequency-amplitude responses that were most similar to natural TM at lower frequencies were for graft thicknesses of 0.2 mm and for 0.1 mm at higher frequencies. Second, in cases with 55% posterior perforation of the TM, assessment of the predicted vibration amplitude of different thicknesses of the cartilage plate showed that a cartilage plate of less than 0.2 mm had a frequency response function similar to that of a natural TM in umbo and stapes footplate displacement. Finally, for a central perforation involving 15% of the TM, a cartilage plate of less than 1.0 mm showed a frequency response function similar to that of TM in umbo and stapes-footplate displacement. CONCLUSIONS: On the basis of our biomechanical analysis, the optimal thickness of a cartilage graft for myringoplasty appears to be 0.1 to 0.2 mm for medium and large TM perforations. For small perforations, a cartilage of less than 1.0 mm is a good compromise between mechanical stability and low acoustic transfer loss.     

Experimental ossicular fixations and the middle ear's response to sound: evidence for a flexible ossicular chain

A human temporal-bone preparation was used to determine the effects of various degrees of artificial ossicular fixation on the sound-induced velocity at the input-side (the umbo of the malleus) and the output-side (the stapes) of the ossicular chain. Construction of various degrees of attachment between an ossicle and the surrounding temporal bone provided a range of reduction in ossicular mobility or "fixations". The results demonstrate different effects of the fixations on the umbo and stapes velocity: fixations of the stapes or incus produce larger reductions in sound-induced stapes velocity (as much as 40-50 dB with extensive stapes fixation), than reductions in umbo velocity (typically less than 10 dB). Fixations of the malleus produce similar-sized changes in both umbo and stapes velocity. These differential effects are consistent with significant flexibility in the ossicular joints (the incudo-malleolar joint and the incudo-stapedial joint) that permits relative motion between the coupled ossicles. The existence of flexibility in the ossicular joints indicates that joints in the ossicular chain can effect a loss of sound-induced mechanical energy between the umbo and the stapes, with a concomitant reduction in the sound-induced motion of the stapes. The introduction of such losses in sound transmission by the joints raises questions concerning the utility of three ossicles in the mammalian ear. The consequences of ossicular flexibility to ossicular-chain reconstruction is discussed. Also, as examined in a more clinically directed paper [Laryngoscope 115 (2005) 147], the different effects of the various ossicular fixations on the motion of the umbo and malleus may be useful in the diagnosis of the site of fixations in humans with conductive hearing losses caused by such pathologies.     

Estimation of Round-Trip Outer-Middle Ear Gain Using DPOAEs

The reported research introduces a noninvasive approach to estimate round-trip outer-middle ear pressure gain using distortion product otoacoustic emissions (DPOAEs). Our ability to hear depends primarily on sound waves traveling through the outer and middle ear toward the inner ear. The role of the outer and middle ear in sound transmission is particularly important for otoacoustic emissions (OAEs), which are sound signals generated in a healthy cochlea and recorded by a sensitive microphone placed in the ear canal. OAEs are used to evaluate the health and function of the cochlea; however, they are also affected by outer and middle ear characteristics. To better assess cochlear health using OAEs, it is critical to quantify the effect of the outer and middle ear on sound transmission. DPOAEs were obtained in two conditions: (i) two-tone and (ii) three-tone. In the two-tone condition, DPOAEs were generated by presenting two primary tones in the ear canal. In the three-tone condition, DPOAEs at the same frequencies (as in the two-tone condition) were generated by the interaction of the lower frequency primary tone in the two-tone condition with a distortion product generated by the interaction of two other external tones. Considering how the primary tones and DPOAEs of the aforementioned conditions were affected by the forward and reverse outer-middle ear transmission, an estimate of the round-trip outer-middle ear pressure gain was obtained. The round-trip outer-middle ear gain estimates ranged from ?39 to ?17 dB between 1 and 3.3 kHz.     

Diagnosis of Middle Ear Disease with Eardrum Perforation by a Newly Developed Sweep Frequency Measuring Apparatus

Dynamic characteristics of an artificial middle ear model with and without eardrum perforations were measured with our newly developed sweep frequency measuring apparatus. Then, the dynamic characteristics of patients with chronic otitis media having eardrum perforations and with traumatic perforations were measured with this apparatus, and the results were compared with those of the artificial middle ear model with an eardrum perforation. The comparison leads to the conclusion that the middle ear condition of patients with eardrum perforations can be distinguished on the basis of their measurement results. Furthermore, the ossicular chain conditions of patients with eardrum perforations can be diagnosed after putting a paper patch on the eardrum perforation. Therefore, this apparatus seems to be highly useful in the diagnosis of both ossicular chain disorders and eardrum perforations.     

Standardized measurements of the sound transmission of middle ear implants using a mechanical middle ear model

Several ways to evaluate the sound transmission properties of middle ear implants are now established. Besides computer-based simulations using acoustic and electrical analog circuits or finite element analysis, measurements can be performed with temporal bone preparations. Experiments with these preparations consider various anatomical properties, but a large number of parameters influence the outcome of measurements. To facilitate standardized measurements, a mechanical middle ear model was developed that allows comparison of the transfer function of middle ear implants on defined conditions. The model approximates the impedances of the tympanic membrane and inner ear with the aid of thin, flexible membranes. The implants are fit between the membranes, and displacement at an artificial stapes footplate is measured with an optical probe. Fundamental influences on the sound transmission properties of nine different middle ear implants (total ossicular replacement prostheses) were examined. Although the material and shape were different, some of the prostheses revealed very similar transfer functions. The mass of the implant showed the largest influence on sound conduction. With a higher mass, the frequency area above approximately 1 kHz was found to be significantly deteriorated. The lightest implant used was 4 mg and showed the best overall results. These findings show that middle ear prostheses should be as light as possible for optimum high-frequency transmission. Received: 24 May 1998 / Accepted: 9 July 1998     

Tympanic membrane/middle ear pathologic correlates in chronic otitis media.

OBJECTIVE: To correlate pathologic findings of the tympanic membrane with pathologic changes in the middle ear cleft in chronic otitis media. STUDY DESIGN: Retrospective. MATERIAL AND METHODS: One hundred-fifty temporal bones from 97 subjects with chronic otitis media (defined as middle ear pathologic changes including granulation tissue, fluid, cholesteatoma, cholesterol granuloma, tympanosclerosis, and ossicular changes) were selected to correlate the presence of these middle ear pathologies with histopathologic changes of the tympanic membrane. The tympanic membrane pathologies included perforation, myringosclerosis, retraction, hemorrhage, fluid-filled cystic spaces, or dilated vessels. Temporal bones were also assessed for atelectasis. Fifty-six normal temporal bones were taken as controls for measurements. RESULTS: Significant correlations between tympanic membrane and middle ear pathology included myringosclerosis and granulation tissue, myringosclerosis and ossicular pathology, retraction and cholesterol granuloma, retraction and cholesteatoma, retraction and ossicular pathology, perforation and ossicular pathology, and hemorrhage and granulation tissue. Additive effects of some pathologies were also observed. Almost half the bones with middle ear pathology had no associated tympanic membrane pathology, whereas multiple pathologic changes in the tympanic membrane generally showed underlying multiple pathologic changes in the middle ear. CONCLUSION: When tympanic membrane pathology is detected otoscopically, its presence, alone or in combination, can be a strong indicator of underlying middle ear pathology. However, a normal-appearing tympanic membrane does not exclude the possibility of middle ear pathology. These findings suggest the need for other diagnostic tools such as multifrequency tympanometry and otoacoustic emissions to complement otoscopy for diagnosis of middle ear pathology, especially in a tympanic membrane that appears "normal."     

慢性化脓性中耳炎术前检查指标和听骨链状态的相关性分析

目的:探讨慢性化脓性中耳炎术前检查指标和听骨链状态的相关性。方法:回顾性分析251例(288 耳)慢性化脓性中耳炎患者的听骨链状态与鼓膜穿孔类型、术前是否干耳、气导阈值、骨气导差值、乳突汽化程度、 耳源性并发症及胆脂瘤之间的相关性。结果:听骨链中断患者的气导阈值和骨气导差值明显增加;鼓膜松弛部穿 孔、术前持续流脓、存在胆脂瘤耳以及出现并发症耳的听骨链中断发生率明显增加。结论:根据纯音听阈可大致 判断听骨链的完整性和活动度;同时,听骨链状况与鼓膜穿孔类型、术前是否干耳、胆脂瘤耳和耳源性并发症耳具 有明显相关性。     

Management of brain herniation and cerebrospinal fluid leak in revision chronic ear surgery

OBJECTIVES/HYPOTHESIS: Brain herniation and cerebrospinal fluid (CSF) leakage into the middle ear and mastoid are rare but described complications of chronic ear disease. This paper will discuss the presentation and management of brain herniation and/or CSF leak encountered in revision chronic ear surgery. STUDY DESIGN: Retrospective chart review. METHODS: Twelve of 1,130 cases of revision chronic ear surgery in which brain herniation or CSF leak was diagnosed were identified and analyzed. RESULTS: Ten (83%) patients' initial diagnosis was tympanic membrane (TM) perforation with cholesteatoma and two (17%) with TM perforation without cholesteatoma. Initial revision procedures included one (8.3%) tympanoplasty with canal-wall-up mastoidectomy maintaining ossicular continuity, two (17%) tympanoplasties with canal-wall-down (CWD) mastoidectomies with ossicular chain reconstruction (OCR), and nine (75%) tympanoplasties with CWD mastoidectomies without OCR. Three (25%) required a second procedure, two (17%) a third, and one (8.3%) a fourth, finally resulting in four (33%) with an ossicular reconstruction and eight (67%) without. Brain herniation and/or CSF leak were repaired by way of transmastoid and middle fossa approaches. Preoperative and postoperative pure-tone average air-bone gaps were statistically similar (33.1 and 28.1 dbHL, respectively; P = .464). CONCLUSIONS: Brain herniation and/or CSF leak appear to be rare complications of surgery for revision chronic ear disease. Their management require adherence to the principles of establishing a safe ear with hearing restoration as a secondary goal.     

Mechanisms of Tympanic Membrane and Incus Mobility Loss in Acute Otitis Media Model of Guinea Pig

Acute otitis media (AOM) is a rapid infection of middle ear due to bacterial or viral invasion. The infection commonly leads to negative pressure and purulent effusion in the middle ear. To identify how these changes affect tympanic membrane (TM) mobility or sound transmission through the middle ear, we hypothesize that pressure, effusion, and structural changes of the middle ear are the main mechanisms of conductive hearing loss in AOM. To test the hypothesis, a guinea pig AOM model was created by injection of Streptococcus pneumoniae. Three days post inoculation, vibration of the TM at umbo in response to input sound in the ear canal was measured at three experimental stages: intact, pressure-released, and effusion-drained AOM ears. The vibration of the incus tip was also measured after the effusion was removed. Results demonstrate that displacement of the TM increased mainly at low frequencies when pressure was released. As the effusion was removed, the TM mobility increased further but did not reach the level of the normal ear at low frequencies. This was caused by middle ear structural changes or adhesions on ossicles in AOM. The structural changes also affected movement of the incus at low and high frequencies. The results provide new evidence for understanding the mechanism of conductive hearing loss in AOM.     

中耳传声过程中砧镫关节声损失的研究

目的为了研究声音在中耳传递过程中在砧镫关节上的声损失,深入了解中耳传声中的机制和方式,并探讨其意义,为中耳手术中听骨链重建,尤其是为耳硬化手术中镫骨赝复物与砧骨长脚的嵌合的理想程度寻找理论依据。方法本试验研究了17个新鲜颞骨标本。用2个颞骨进行了机械刺激时的磁场矫正。采用激光多普勒振动仪,分别在声刺激和机械刺激下,对15个新鲜颞骨标本进行了研究。首先测量在80dB声刺激(声压级,下同)下镫骨底板的位移,然后在机械刺激条件下得到等同于80dB声刺激的镫骨底板位移以建立试验体系并保证试验体系的准确性。在等同于80dB声刺激的机械刺激条件下,测量10个颞骨标本砧镫关节的声损失。结果在所测量的频率中,砧镫关节上的声损失在3dB以内。结论中耳传声过程中,在砧镫关节上存在着声损失,这种损失是生理性和保护性的。     

Measurement of Basilar Membrane Motion During Round Window Stimulation in Guinea Pigs

Driving the cochlea in reverse via the round window membrane (RWM) is an alternative treatment option for the hearing rehabilitation of a nonfunctional or malformed middle ear. However, cochlear stimulation from the RWM side is not a normal sound transmission pathway. The basilar membrane (BM) motion elicited by mechanical stimulation of the RWM is unknown. In this study, the BM movement at the basal turn was investigated in both reverse via RWM drive and acoustic stimulation in the ear canal or forward drive in postmortem isolated temporal bone preparations of guinea pigs. During reverse drive, a magnet-coil was coupled on RWM, and the BM vibration at the basal turn and the movement of the incus tip were measured with laser Doppler vibrometry. During forward drive, the vibration of the incus tip induced by sound pressure in the ear canal resulted in BM vibration and the BM movement at the same location as that in the reverse stimulation was measured. The displacement ratio of the BM to RWM in reverse drive and the ratio of the BM to incus in forward drive were compared. The results demonstrated that the BM response measured in both situations was similar in nature between forward and reverse drives. This study provides new knowledge for an understanding of BM movement induced by reverse drive via the RWM stimulation.     

The Aging of the Middle Ear in 129S6/SvEvTac and CBA/CaJ Mice: Measurements of Umbo Velocity,Hearing Function,and the Incidence of Pathology

Measurements of umbo velocity and auditory brainstem response (ABR) were made on two different strains of mice, 129S6/SvEvTac (129S6) and CBA/CaJ (CB), within three different age ranges. The velocity measurements were made with a laser Doppler vibrometer using a semiclosed sound delivery system; the frequency range of accurate velocity measurements is from 1 to 21 kHz. The visual detection threshold of the ABR was determined at selected frequencies between 2 and 32 kHz. The velocity results suggest a small but significant change in umbo velocity with age in both strains, between the youngest (1.5–3 months) and mid-aged (12–14 months) groups. There is also a clear difference in the umbo velocity in the youngest animals of the two strains, with the 129S6 having more sensitive middle-ear function than the CB. These results support the existence of a small age-related loss in middle-ear sensitivity in the mouse that was first described in the BALB/6J strain. The age-related changes in middle-ear function observed in both CB and 129S6 are much smaller than the age-related decreases in ABR. Our results also describe a statistically significant increase in the incidence of middle-ear pathology with age in the 129S6.     

Ossicular vibration in human temporal bones

Vibration mode of the ossicles was investigated in twelve fresh human temporal bones using a video measuring system (VMS, Technical Instrument). This system allows one to observe the ossicular vibration and to measure its vibration amplitude (up to 0.2 micron) and phase angle. In this study the inner and middle ear was kept intact except for two small holes in the tympanic tegmen. These holes were for the observation of ossicular movement and were covered with a thin cover glass during the experiment. The vibration amplitude and phase angle of the umbo, malleus head, lenticular process and stapes head were measured at 19 frequencies between 0.1 kHz and 4.5 kHz. The umbo moved piston-like at 0.1-0.8 kHz and 2.6-4.5 kHz but in an ellipse at 1.0-2.4 kHz. The malleus head showed elliptical movement with its long axis anteriorly tilted around 45 degrees from the direction of the umbo vibration at 0.1 kHz. Both the lenticular process and stapes head showed similar movement; piston-like in lower frequencies and elliptical in higher frequencies. The umbo, lenticular process and stapes head vibrated parallel at lower frequencies. The position, displacement and phase angle of the rotation axis of the ossicles was calculated based on the displacement and phase angle of the umbo, malleus head and lenticular process. The axis was around the level of the neck of the malleus in frequencies lower than the resonant frequency, beneath the level of the short process near the resonant frequency and at the top of the malleus head in higher frequencies. The average axis displacement was 0.9 microns at 1 kHz but much smaller at frequencies lower than 0.8 kHz or higher than 2 kHz. This suggests that such axis movement may reduce the efficiency of the middle ear sound transmission.     

The Conductive Hearing Loss Due to an Experimentally Induced Middle Ear Effusion Alters the Interaural Level and Time Difference Cues to Sound Location

Otitis media with effusion (OME) is a pathologic condition of the middle ear that leads to a mild to moderate conductive hearing loss as a result of fluid in the middle ear. Recurring OME in children during the first few years of life has been shown to be associated with poor detection and recognition of sounds in noisy environments, hypothesized to result due to altered sound localization cues. To explore this hypothesis, we simulated a middle ear effusion by filling the middle ear space of chinchillas with different viscosities and volumes of silicone oil to simulate varying degrees of OME. While the effects of middle ear effusions on the interaural level difference (ILD) cue to location are known, little is known about whether and how middle ear effusions affect interaural time differences (ITDs). Cochlear microphonic amplitudes and phases were measured in response to sounds delivered from several locations in azimuth before and after filling the middle ear with fluid. Significant attenuations (20–40 dB) of sound were observed when the middle ear was filled with at least 1.0 ml of fluid with a viscosity of 3.5 Poise (P) or greater. As expected, ILDs were altered by ~30 dB. Additionally, ITDs were shifted by ~600 μs for low frequency stimuli (<4 kHz) due to a delay in the transmission of sound to the inner ear. The data show that in an experimental model of OME, ILDs and ITDs are shifted in the spatial direction of the ear without the experimental effusion.     

中耳机械模型的建立及听骨赝复物传音特性的研究

目的探讨对人工听骨赝复物传音功能进行评价的客观方法，以及钛金属人工听骨赝复物不同质量和不同顶盘面积在中耳机械模型中对传音功能的影响。方法用两块圆形的弹性膜分别代替鼓膜和前庭窗，两膜之间放置人工听骨，在人工外耳道侧给予纯音刺激，同时记录其声强，在前庭窗膜处用激光测振仪测量前庭窗膜的振动速度，通过比较振动速度的大小来比较人工听骨的传音特性；将质量不同和面积不同的2组钛人工听骨分别安放于中耳机械模型中测量其传音特性。结果模型感觉阈曲线和正常人听阈曲线对比，两者走势基本相同。钛听骨顶盘面积较小的听骨在1500-4000Hz其传音特性优于顶盘面积较大的听骨；质量小的听骨在高频区传音好，质量大的听骨在低频区传音比较好，但总体上质量小的听骨传音特性较好。结论中耳机械模型是检验人工听骨传音特性并进行人工听骨赝复物客观评价的理想工具之一；钛人工听骨的质量和顶盘的面积对其传音特性均有影响，在设计人工听骨时或手术要同时考虑到质量和顶盘面积对传音的影响。