Tracking cell layer contribution during repair of the tympanic membrane.

The tympanic membrane (i.e. eardrum) sits at the interface between the middle and external ear. The tympanic membrane is composed of three layers: an outer ectoderm-derived layer, a middle neural crest-derived fibroblast layer with contribution from the mesoderm-derived vasculature, and an inner endoderm-derived mucosal layer. These layers form a thin sandwich that is often perforated following trauma, pressure changes or middle ear inflammation. During healing, cells need to bridge the perforation in the absence of an initial scaffold. Here, we assessed the contribution, timing and interaction of the different layers during membrane repair by using markers and reporter mice. We showed that the ectodermal layer is retracted after perforation, before proliferating away from the wound edge, with keratin 5 basal cells migrating over the hole to bridge the gap. The mesenchymal and mucosal layers then used this scaffold to complete the repair, followed by advancement of the vasculature. Finally, differentiation of the epithelium led to formation of a scab. Our results reveal the dynamics and interconnections between the embryonic germ layers during repair and highlight how defects might occur.

Tympanic membrane perforations cannot be reliably detected using computed tomography based on 15 cadaver dogs.

The integrity of the tympanic membrane is an important factor when deciding treatment and therapeutic recommendations for dogs with ear disease; however, otoscopic examination may be difficult to perform due to features of external ear canal disease or patient compliance. CT is useful for the evaluation of middle ear disease, including cases in which middle ear disease is detected incidentally. The tympanic membrane is detectable using CT, but anecdotally, apparent focal defects or discontinuities of the tympanic membrane are often seen in patients with and without ear disease. The purpose of this prospective, observer agreement study was to determine if perforations of the tympanic membrane are reliably detectable on CT. Fifteen cadaver dogs underwent CT and video otoscopy to verify the integrity of each tympanic membrane. Cadavers were randomly assigned to have the tympanic membranes left intact or to undergo a myringotomy on either the left, the right, or both sides. CT was performed immediately following the myringotomies. Four blinded evaluators evaluated the pre- and post-myringotomy scans for a total of 30 scans (60 tympanic membranes). Average accuracy was low (44%), and interobserver agreement for all four evaluators was fair. Although the tympanic membrane is visible on CT, perforations of the tympanic membrane are unlikely to be accurately detected or excluded. The appearance of an intact tympanic membrane or defect in the membrane on CT should not be used as criteria to guide clinical treatment recommendations based on this cadaver model.

[The technique and application of individualized tympanic membrane flap in the repair of tympanic membrane under endoscopy ear surgery].

Objective:To investigate the technique of personalized flap making under otoscopy and its clinical application. Methods:The clinical data of patients who underwent 301 Military Hospital myringoplasty in the Department of otoendoscopic surgery, Department of Otorhinolaryngology, head and neck surgery, Department of Otorhinolaryngology, from October 2022 to 2023 August were analyzed retrospectively, all enrolled patients were performed independently by the same skilled otoendoscopic surgeon. The patients' general condition, medical history, tympanic membrane perforation scope, perforation size, need for tympanic cavity exploration, thickness of skin flap, tympanic cavity lesion scope, skin flap making method and postoperative rehabilitation were collected. Results:Many factors such as the location of tympanic membrane perforation, the thickness of the skin flap, the degree of curvature or stricture of the ear canal and the extent of the lesion in the tympanic cavity should be considered in the manufacture of the individualized tympanic membrane skin flap, the way of skin flap making does not affect the long-term postoperative rehabilitation, but it can effectively avoid unnecessary ear canal skin flap injury and improve the operation efficiency. Conclusion:Scientific flap fabrication is important for improving surgical efficiency and enhancing surgical confidence.

A Proof-of-Concept Computer Vision Approach for Measurement of Tympanic Membrane Perforations.

OBJECTIVE: Size, an important characteristic of a tympanic membrane perforation (TMP), is commonly assessed with gross estimation via visual inspection, a practice which is prone to inaccuracy. Herein, we demonstrate feasibility of a proof-of-concept computer vision model for estimating TMP size in a small set of perforations. METHODS: An open-source deep learning architecture was used to train a model to segment and calculate the area of a perforation and the visualized tympanic membrane (TM) in a set of endoscopic images of mostly anterior and relatively small TMPs. The model then computed relative TMP size by calculating the ratio of perforation area to TM area. Model performance on the test dataset was compared to ground-truth manual annotations. In a validation survey, otolaryngologists were tasked with estimating the size of TMPs from the test dataset. The primary outcome was the average absolute error of model size predictions and clinician estimates compared to sizes determined by ground-truth manual annotations. RESULTS: The model's average absolute error for size predictions was a 0.8% overestimation for all test perforations. Conversely, among the 38 survey respondents, the average clinician error was a 11.0% overestimation (95% CI, 5.2-16.7%, p = 0.003). CONCLUSIONS: In a small sample of TMPs, we demonstrated a computer vision approach for estimating TMP size is feasible. Further validation studies must be done with significantly larger and more heterogenous datasets. LEVEL OF EVIDENCE: N/A Laryngoscope, 134:2906-2911, 2024.

Prophylactic antibiotics has no benefit for outcome in clean myringoplasty-A register-based cohort study from SwedEar.

OBJECTIVES: To investigate if prophylactic antibiotics (PA) in conjunction with myringoplasty of clean and uninfected ears entails a reduction of postoperative infections within 6 weeks after surgery, and whether it affects the healing rate of the tympanic membrane (TM) at follow-up, 6-24 months after surgery. DESIGN: A retrospective cohort study of prospectively collected data. SETTING: Data extracted from The Swedish Quality Register for Ear Surgery (SwedEar), the years 2013-2019. PARTICIPANTS: All patients in SwedEar with a registered clean conventional myringoplasty (tympanoplasty type I) including a follow-up visit. MAIN OUTCOME MEASURES: The effect of PA use on TM healing rate at follow-up and postoperative infection within 6 weeks of surgery. RESULTS: In the study group (n = 1665) 86.2% had a healed TM at follow-up. There was no significant difference between the groups that had PA administered (87.2%) or not (86.1%). A total of 8.0% had a postoperative infection within 6 weeks. Postoperative infection occurred in 10.2% of the group that received PA (n = 187) compared with 7.7% of the group that did not receive PA. However, this difference was not statistically significant. Postoperative infection within 6 weeks significantly lowered the frequency of healed TMs. CONCLUSION: PA administered during clean conventional myringoplasty does not improve the chance of having a healed TM at follow up, nor decrease the risk of having a postoperative infection within 6 weeks after surgery.

Endoscopic transtympanic cartilage push-through myringoplasty without tympanomeatal flap elevation for tympanic membrane perforation.

BACKGROUND: The elevation of the tympanomeatal flap in endoscopic myringoplasty will cause considerable tissue damage. OBJECTIVE: To analyze anatomic and audiological results of tympanic membrane perforation underwent endoscopic transtympanic cartilage push-through myringoplasty without tympanomeatal flap elevation (EPM) and their relationship with the size of perforation. METHODS: A clinical retrospective study was performed on 75 cases of tympanic membrane perforation that underwent EPM from January 2019 to March 2021. Graft success and hearing outcomes were evaluated 3 months after surgery. RESULTS: The overall graft success rate for EPM was 94.7% (71/75). The total rate of hearing success, postoperative ABG ≤ 20 dB was achieved in 96.0% (72/75). The overall mean AC threshold of 35.1 ± 5.6 dB was lowered to 25.0 ± 4.8 dB postoperatively (p < .01). The mean pre- and postoperative ABG of all patients were 20.5 ± 4.6 dB and 10.4 ± 3.9 dB (p < .01), respectively. The graft success rates for the small, middle and large perforations groups were 100% (11/11), 100% (34/34) and 86.7% (26/30), respectively. CONCLUSION: It is revealed that EPM is an effective method to repair perforation of tympanic membrane. The size of the tympanic membrane perforation may be a risk factor for perforation healing and hearing recovery, although EPM is available for large perforations.

Paper Patching Versus Watchful Waiting of Traumatic Tympanic Membrane Perforations: A Meta-Analysis.

OBJECTIVES/HYPOTHESIS: The aim of the study was to investigate the healing rates, the restoration of hearing, and the time for complete healing of paper patching versus watchful waiting for traumatic tympanic membrane perforations (TTMPs). STUDY DESIGN: Systematic review with meta analysis. METHODS: Publications were selected by a search on "PubMed," "Embase," and "Web of Science." A meta-analysis of risk ratios for paper patching (intervention arm) and watchful waiting (control arm) was performed. RESULTS: Five studies describing 393 TTMPs were included in the quantitative meta-analysis. TTMP healing rates ranged between 84.2% and 95.2% in the intervention arm and between 76.7% and 84.8% in the control arm. The pooled risk ratio of healed TTMPs was significantly higher in the intervention arm than in the control arm (risk ratio: 1.12, 95% confidence interval: 1.04-1.21). CONCLUSIONS: TTMPs have high healing potential with and without intervention. The healing rate of paper patching was superior to that of watchful waiting alone. LEVEL OF EVIDENCE: NA Laryngoscope, 131:2091-2097, 2021.

Endaural Over-Underlay Cartilage Tympanoplasty for Repair of Dry Subtotal Perforations.

OBJECTIVES: We explored the auditory and anatomical success of grafting when the cartilage perichondrium (CP) was prepared using two different methods. METHODS: Patients with subtotal or total perforation underwent tympanoplasty with a CP graft. A V-shaped groove for the handle of the malleus was prepared for CP grafts in patients in group 1. Patients in group 2 did not have a groove on the graft. The anatomical success of the graft was evaluated as success, partial success, or failure. Results of auditory evaluations were compared between the two groups. RESULTS: A total of 195 patients were included in the study. The total CP graft integration rate was 96% for both groups. Significant changes were detected in all hearing criteria evaluated 12 months after surgery compared to the preoperative period (P < .05). There were no significant differences between the groups in terms of the relationship between graft technique and postoperative hearing results. However, rates of partial success were significantly higher for group 1 than group 2 (P = .033). CONCLUSION: Cartilage slice support offers an extremely reliable method for reconstruction of tympanic membrane in cases of high-risk perforation. Partial failures are rare, but when they occur, they most often involved anterior graft medialization. When a piece of cartilage is removed at the malleus interface there may be a higher rate of partial failure.

Central versus marginal tympanic membrane perforations: does it matter? An analysis of 792 patients.

BACKGROUND: There is a lack of studies concerning chronic otitis media without cholesteatoma. OBJECTIVES: To perform an analysis of tympanic membrane perforations (TMP), compare the parameters of central and marginal TMP, combining both the traditional and more recent technologies available. MATERIAL AND METHODS: 792 consecutive patients. The TMP subgroups were divided by central and marginal locations and compared based on signs suggestive of previous tympanic retraction, namely, medialized malleus, tympanic remnants over the promontory, tympanic remnants over the ossicular chain, and incus/stapes erosion. Analysis of the status of the contralateral ear (CLE). RESULTS: Central TMP was diagnosed in 79.8%. Compared with the central group, the marginal group had more reported hearing loss (95.6%), greater conductive hearing loss (pure tone average for air-conduction 43.3 dB and average air-bone gap of 28.7 dB), a larger perforated area (46.45%), more posteroinferior quadrant involvement, a greater number retraction signs prior to the TMP, and more changes in the CLE (71%). CONCLUSION: The differences between TMP subgroups are highlighted when we use all technologies available to compare them. Marginal TMPs have more altered parameters than central TMPs. SIGNIFICANCE: There is a great possibility to enhance the knowledge of TMPs and to improve the pathogenesis-based treatment.

The Effect of External Auditory Canal Packing Duration on Healing After Endoscopic Cartilage Myringoplasty.

INTRODUCTION: The external auditory canal (EAC) packing is widely used in otosurgery and is considered to promote hemostasis and to support tympanic membrane grafts. However, few studies have investigated the effects of packing removal time on healing. OBJECTIVE: We investigated the effect of EAC packing duration on healing after endoscopic cartilage myringoplasty in patients with chronic tympanic membrane perforations (TMPs). MATERIALS AND METHODS: Patients with chronic TMPs who underwent endoscopic "push-through" cartilage myringoplasty were divided into early and late groups based on the length of time before EAC packing was removed. The graft success rate, eardrum appearance, and hearing gain were assessed 3 months after surgery. RESULTS: The study included 137 patients. Three months after surgery, the graft success rate was 83.5% (66/79) in the early group and 94.8% (55/58) in the late group (P = .042). The graft was displaced in 8 (10.1%) patients in the early group and in 1 (1.7%) patient in the late group (P = .050). No epithelialization was found on the surface of the grafts in the early group, whereas epithelialization was nearly complete 4 weeks after surgery in the late group. CONCLUSIONS: Delaying removal of the EAC packing after endoscopic cartilage myringoplasty may promote tympanic membrane better healing and cartilage graft epithelialization and improve the appearance of the eardrum.

Histological Study of The Healing of Traumatic Tympanic Membrane Perforation After Vivosorb and Epifilm Application.

BACKGROUND: Untreated traumatic tympanic membrane perforations (TMPs) may lead to permanent perforations and hearing loss. There are many materials that have been previously used for repairing the TMPs. AIMS AND OBJECTIVES: The purpose of this study is to evaluate the clinical and histological effects of Vivosorb (Vv) and Epifilm on healing of TMPs in a rat model. MATERIAL AND METHODS: The posterior-inferior quadrant of the tympanic membranes (TMs) in right ears of 14 rats was perforated using a 20-g needle and then the animals were randomly divided into 2 equal groups (n = 7). The perforated right TMs were treated with either Vv (Vv group) or Epifilm (Ep group). The left TMs of 7 rats were perforated in same way and allowed to close spontaneously without any topical material applications (spontaneous closure group as sham control, SC). The left tympanic membranes of the other 7 rats were not perforated and used as normal controls (NC group). On postoperative 15th day, tympanic bullas were extracted from killed rats and examined morphometrically and histopathologically. RESULTS: Perforation closure rate was 85.7% (6/7) in both Vv and SC groups. Perforations of Ep group closed in 7/7 (100%) ears. The thicknesses of the perforated membranes were increased in SC and especially Vv groups. Also, connective tissue fibrosis, blood clots, and epithelial degenerations were detected in SC and Vv groups. The mean fibroblastic reaction scores of Vv, Ep, and SC groups were 2.14(+), 0.57(+), and 1.71(+) respectively, on comparison with NC group. The mean neovascularization score was 1.42(+) in Vv group, 0.14(+) in Ep group, and 0.57(+) in SC group. CONCLUSION AND SIGNIFICANCE: Vivosorb and especially Epifilm can improve the healing process in traumatic TMPs and additionally, Epifilm might be more preferred for the treatment of TMPs because of causing lesser fibrosis.

Necessities, opportunities, and challenges for tympanic membrane perforation scaffolding-based bioengineering.

Tympanic membrane (TM) perforation is a global clinical dilemma. It occurs as a consequence of object penetration, blast trauma, barotrauma, and middle ear diseases. TM perforation may lead to otitis media, retraction pockets, cholesteatoma, and conductive deafness. Molecular therapies may not be suitable to treat perforation because there is no underlying tissue matrix to support epithelium bridging. Chronic perforations are usually reconstructed with autologous grafts via surgical myringoplasty. Surgical treatment is uncomfortable for the patients. The grafting materials are not perfect because they produce an opaque membrane, fail in up to 20% of cases, and are suboptimal to restore acoustic function. Millions of patients from developing parts of the world have not got access to surgical grafting due to operational complexities, lack of surgical resources, and high cost. These shortcomings emphasize bioengineering to improve placement options, healing rate, hearing outcomes, and minimize surgical procedures. This review highlights cellular, structural, pathophysiological, and perforation specific determinants that affect healing, acoustic and surgical outcomes; and integrates necessities relevant to bioengineered scaffolds. This study further summarizes scaffolding components, progress in scaffolding strategies and design, and engenders limitations and challenges for optimal bioengineering of chronic perforation.

From Toothpick to Intraparenychmal Otogenic Pneumocephalus: A Case Report.

BACKGROUND: Intracranial pneumocephalus, the accumulation of air, occurs most frequently from trauma, tumor, cranial surgeries, or infection. Intraparenchymal otogenic pneumocephalus is a rare but well-documented development. We describe a patient who developed pneumocephalus in the context of eardrum perforation secondary to toothpick use for ear wax. CASE DESCRIPTION: An 86-year-old female presented to the emergency room with a 1-day history of dysarthria and a few days of cough and sneezing. History revealed she had recently been advised to avoid Q-Tips to clean her ears and instead was using toothpicks. She denied otalgia or otorrhea and had no signs of infection near the ear. On otoscopic examination, the right tympanic membrane was perforated. On head computed tomography, she was found to have a large right temporal pneumocephalus extending from the petrous bone. Magnetic resonance imaging of the brain revealed a defect in the right tegmen. She was started on empiric antibiotics and subsequently taken to the operating room for craniotomy and repair of bony and dural defects. CONCLUSIONS: Otogenic pneumocephalus is a rare occurrence. This is the first reported case of pneumocephalus related to self-induced middle ear trauma with a toothpick that ultimately required craniotomy for repair.

The Development of a Tympanic Membrane Model and Probabilistic Dose-Response Risk Assessment of Rupture Because of Blast.

INTRODUCTION: There is no dose-response model available for the assessment of the risk of tympanic membrane rupture (TMR), commonly known as eardrum rupture, from exposures to blast from nonlethal flashbangs, which can occur concurrently with temporary threshold shift. Therefore, the objective of this work was to develop a fast-running, lumped parameter model of the tympanic membrane (TM) with probabilistic dose-dependent prediction of injury risk. MATERIALS AND METHODS: The lumped parameter model was first benchmarked with a finite element model of the middle ear. To develop the dose-response curves, TMR data from a historic cadaver study were utilized. From these data, the binary probability response was constructed and logistic regression was applied to generate the respective dose-response curves at moderate and severe eardrum rupture severity. RESULTS: Hosmer-Lemeshow statistical and receiver operation characteristic analyses showed that maximum stored TM energy was the overall best dose metric or injury correlate when compared with total work and peak TM pressure. CONCLUSIONS: Dose-response curves are needed for probabilistic risk assessments of unintended effects like TMR. For increased functionality, the lumped parameter model was packaged as a software library that predicts eardrum rupture for a given blast loading condition.

Hearing Damage Induced by Blast Overpressure at Mild TBI Level in a Chinchilla Model.

INTRODUCTION: The peripheral auditory system and various structures within the central auditory system are vulnerable to blast injuries, and even blast overpressure is at relatively mild traumatic brain injury (TBI) level. However, the extent of hearing loss in relation to blast number and time course of post-blast is not well understood. This study reports the progressive hearing damage measured in chinchillas after multiple blast exposures at mild TBI levels (103-138 kPa or 15-20 psi). MATERIALS AND METHODS: Sixteen animals (two controls) were exposed to two blasts and three blasts, respectively, in two groups with both ears plugged with foam earplugs to prevent the eardrum from rupturing. Auditory brainstem response (ABR) and distortion product otoacoustic emission (DPOAE) were measured in pre- and post-blasts. Immunohistochemical study of chinchilla brains were performed at the end of experiment. RESULTS: Results show that the ABR threshold and DPOAE level shifts in 2-blast animals were recovered after 7 days. In 3-blast animals, the ABR and DPOAE shifts remained at 26 and 23 dB, respectively after 14 days. Variation of auditory cortex damage between 2-blast and 3-blast was also observed in immunofluorescence images. CONCLUSIONS: This study demonstrates that the number of blasts causing mild TBI critically affects hearing damage.

Computer simulation study of the penetration of pulsed 30, 60 and 90 GHz radiation into the human ear.

There is increasing interest in applications which use the 30 to 90 GHz frequency range, including automotive radar, 5 G cellular networks and wireless local area links. This study investigated pulsed 30-90 GHz radiation penetration into the human ear canal and tympanic membrane using computational phantoms. Modelling involved 100 ps and 20 ps pulsed excitation at three angles: direct (orthogonal), 30° anterior, and 45° superior to the ear canal. The incident power flux density (PD) estimation was normalised to the International Commission on Non-Ionizing Radiation Protection (1998) standard for general population exposure of 10 Wm-2 and occupational exposure of 50 Wm-2. The PD, specific absorption rate (SAR) and temperature rise within the tympanic membrane was highly dependent on the incident angle of the radiation and frequency. Using a 30 GHz pulse directed orthogonally into the ear canal, the PD in the tympanic membrane was 0.2% of the original maximal signal intensity. The corresponding PD at 90 GHz was 13.8%. A temperature rise of 0.032° C (+20%, -50%) was noted within the tympanic membrane using the equivalent of an occupational standard exposure at 90 GHz. The central area of the tympanic membrane is exposed in a preferential way and local effects on small regions cannot be excluded. The authors strongly advocate further research into the effects of radiation above 60 GHz on the structures of the ear to assist the process of setting standards.

Assessment of hearing loss induced by tympanic membrane perforations under blast environment.

PURPOSES: This study provides an approach to estimating tympanic membrane perforation-induced hearing loss (HL) using a human middle ear model. METHODS: Sixty-one cases of tympanic membrane perforation originating from fireworks were reported from the Ear-Nose-Throat Department. The otoscope, audiometry data and diagnosis records were organized, and gender, age, etiology, perforation size and diseased ear side were classified as independent variables. A multinomial regression model was used to analyze the potential effects of the variables on HL. Meanwhile, a human middle ear model was implemented to calculate the ensued HL resulting from different perforation areas and sites. In addition, linear regression models were used to establish functions between perforation size and HL. RESULTS: The audiometry data indicate that HL at high frequencies (f > 2 kHz) is much more profound than that at the speech frequency band (f < 1 kHz). Compared with mild HL (<15 dB), mediate HL (15-30 dB) was correlated with the perforation area (p < 0.05, 95% CI), while severe HL (>30 dB) was affected by both perforation size and age (p < 0.05, 95% CI). However, other factors, including gender and diseased ear side, do not show a statistically significant effect on HL. Furthermore, the Kruskal-Wallis test result reveals that HL at frequencies of 0.25 kHz ≤ f ≤ 8 kHz is strongly associated with the perforation size (p < 0.05, 95% CI). CONCLUSIONS: It is conclusive that HL is positively proportional to the perforation size. However, HL is not correlated with the perforation site for small perforation areas of < 10% (p > 0.05, 95% CI).

The effects of everted or inverted edges on healing of traumatic-induced tympanic membrane perforations.

OBJECTIVES: To evaluate the healing and hearing outcomes related to the everted or inverted edge area on slap- and fist-induced large tympanic membrane perforations. METHODS: A total of 120 patients with slap- or fist-induced tympanic membrane perforations, with inverted or everted edges, affecting 50-75 per cent of the entire tympanic membrane, were randomly divided into 2 groups: an edge approximation group and a spontaneous healing group. The edge approximation group was divided into subgroups A and B based on the reversed edge area (reversed edge was more or less than 50 per cent of the total perforation, respectively). Healing outcomes and hearing improvements at six months were compared. RESULTS: The data of 118 patients were analysed. The closure rate of perforations in subgroup A, subgroup B, and the spontaneous healing group was 90.9 per cent, 92.1 per cent and 84.5 per cent, respectively; the difference between the three groups was not significant (p = 0.393). CONCLUSION: The area of reversed edges for slap- or fist-induced tympanic membrane perforations did not seem to affect healing and hearing outcomes, regardless of edge approximation and everted or inverted edges.

Repair of subtotal tympanic membrane perforations: A temporal bone study of several tympanoplasty materials.

The aim of this project was to investigate the effects of different types of graft material, and different remaining segments of the native TM on its motion. In twelve human temporal bones, controlled TM perforations were made to simulate three different conditions. (1) Central perforation leaving both annular and umbo rims of native TM. (2) Central perforation leaving only a malleal rim of native TM. (3) Central perforation leaving only an annular rim of native TM. Five different graft materials (1) perichondrium (2) silastic (3) thin cartilage (4) thick cartilage (5) Lotriderm® cream were used to reconstruct each perforation condition. Umbo and stapes vibrations to acoustic stimuli from 250 to 6349 Hz were measured using a scanning laser Doppler vibrometer. Results showed that at low frequencies: in the Two Rims condition, all grafting materials except thick cartilage and Lotriderm cream showed no significant difference in umbo velocity from the Normal TM, while only Lotriderm cream showed a significant decrease in stapes velocity; in the Malleal Rim condition, all materials showed a significant decrease in both umbo and stapes velocities; in the Annular Rim condition, all grafting materials except Lotriderm and perichondrium showed no significant difference from the Normal TM in stapes velocity. Umbo data might not be reliable in some conditions because of coverage by the graft. At middle and high frequencies: all materials showed a significant difference from the Normal TM in both umbo and stapes velocities for all perforation conditions except in the Annular Rim condition, in which silastic and perichondrium showed no significant difference from the Normal TM at umbo velocity in the middle frequencies. In the low frequencies, the choice of repair material does not seem to have a large effect on sound transfer. Our data also suggests that the annular rim could be important for low frequency sound transfer.