Artificial Ear Research Articles

The area discontinuity between probe and ear canal as a source of power-reflectance measurement-location variability.

This study examined the effect of the area discontinuity between the measurement-probe sound source and ear canal on the plane-wave approximation of power reflectance. The area discontinuity was hypothesized to introduce measurement-location sensitivity to the power reflectance, especially above 5 kHz. Measurements were made in human and artificial ear canals (tubes coupled to an IEC711 ear simulator). In both cases, the power reflectance exhibited a high-frequency notch that decreased in frequency as the residual canal length increased. The area discontinuity between probe and canal was modeled as an inductance in series with the canal's acoustic impedance. To compensate for the effects of the discontinuity, the discontinuity's impedance was subtracted from the measured load impedance of the canal. In the artificial ears, compensation for the estimated area discontinuity removed the high-frequency notch and reduced the position dependence of the power reflectance. Subtracting the estimated discontinuity impedance from the load impedance in the human ears had a minimal effect on the power-reflectance measurement-location variability and magnitude of the high-frequency notch. The area-discontinuity between probe and ear canal is not supported as the primary source of measurement-variability in the plane-wave approximation of the power reflectance in human ears.

Sound pressure distribution in natural or artificial human ear canals in response to mechanical ossicular stimulation

Otoacoustic emissions (OAEs) in the ear canal (EC) are produced by tympanic membrane (TM) and ossicular motion driven by the cochlea. Measurement of OAEs is complicated by nonuniformities in EC sound pressure, which may lead to misinterpretation. Human temporal bones were prepared by removing most of the cartilaginous EC or replacing the bony EC with an artificial EC. The incus was stimulated mechanically through the facial recess by a small piezoelectric actuator to produce TM motion. Sound pressures resulting from broadband stimuli were measured at ~70 locations along the TM surface (Ptm), in the tympanic ring plane 4-6 mm distal to the umbo (Pec), and along the EC axis. Ptm showed considerable transverse spatial variation in narrow frequency bands at frequencies as low as 5 kHz, in contrast to the simpler distribution when sound enters the EC from its lateral end. These transverse variations generally had dissipated at the tympanic ring plane. Longitudinal sound pressure variations along the EC axis we...

Contributions to high-frequency reflectance from the change in diameter between sound-delivery tube and ear canal

Measurement of wideband reflectance requires stimuli to be delivered to the ear canal through a tube with diameter seven-times smaller than that of the average canal. This discontinuity may contribute to the measurement-location sensitivity of reflectance above 5 kHz [Lewis and Neely. (2015). J. Acoust. Soc. Am. 138, 977–993]. To test this hypothesis, reflectance was measured at different locations in a set of artificial ear canals (cylindrical tubes with diameters of 8, 9, and 10 mm) terminated by an IEC711 coupler, and compared to the theoretical reflectance. The measured reflectance exhibited a high-frequency notch that (1) decreased in frequency as distance between the probe and coupler increased and (2) increased in magnitude as canal diameter increased. The theoretical reflectance lacked the high-frequency notch of the measured reflectance; however, it was possible to simulate the measured data by adding an inductance in series with the canal model [Karal. (1953). J. Acoust. Soc. Am. 25, 327–334]. Transforming the impedance measured in the artificial canals to remove the estimated inductance decreased the notch depth and measurement-location sensitivity of the measured reflectance, especially for the larger diameter canals. Additionally, the measured reflectance more-closely approximated the theoretical reflectance. Findings have implications for in-situ sound-level calibrations.

A method to measure sound transmission via the malleus–incus complex

BackgroundThe malleus–incus complex (MIC) plays a crucial role in the hearing process as it transforms and transmits acoustically-induced motion of the tympanic membrane, through the stapes, into the inner-ear. However, the transfer function of the MIC under physiologically-relevant acoustic stimulation is still under debate, especially due to insufficient quantitative data of the vibrational behavior of the MIC. This study focuses on the investigation of the sound transformation through the MIC, based on measurements of three-dimensional motions of the malleus and incus with a full six degrees of freedom (6 DOF). MethodsThe motion of the MIC was measured in two cadaveric human temporal bones with intact middle-ear structures excited via a loudspeaker embedded in an artificial ear canal, in the frequency range of 0.5–5 kHz. Three-dimensional (3D) shapes of the middle-ear ossicles were obtained by sequent micro-CT imaging, and an intrinsic frame based on the middle-ear anatomy was defined. All data were registered into the intrinsic frame, and rigid body motions of the malleus and incus were calculated with full six degrees of freedom. Then, the transfer function of the MIC, defined as velocity of the incus lenticular process relative to velocity of the malleus umbo, was obtained and analyzed. ResultsBased on the transfer function of the MIC, the motion of the lenticularis relative to the umbo reduces with frequency, particularly in the 2–5 kHz range. Analysis of the individual motion components of the transfer function indicates a predominant medial-lateral component at frequencies below 1 kHz, with low but considerable anterior-posterior and superior-inferior components that become prominent in the 2–5 kHz range. ConclusionThe transfer function of the human MIC, based on motion of the umbo and lenticularis, has been visualized and analyzed. While the magnitude of the transfer function decreases with frequency, its spatio-temporal complexity increases significantly.

The role of the Utah Artificial Ear project in the development of the modern cochlear implant

The cochlear implant has provided the first substantial restoration of a human sense by a medical intervention. This accomplishment was brought about by the efforts, over a 50+ year period, of many individuals in laboratories around the world. In this paper, we recount the history of one of the early projects – the Utah Artificial Ear project. In 1970 researchers at the University of Utah began work on an auditory prosthesis. A critical early decision was to create a ‘transparent’ link between external signal processing and the electrodes implanted in the cochlea, i.e., a percutaneous pedestal. The pedestal allowed D. Eddington, then a graduate student, to conduct, in 1975–1978, the first thorough, parametric, psychophysical studies of electrical stimulation of the cochlea in multiple human volunteers. The early work by Eddington and colleagues evolved in 1983 into the 4-channel, Ineraid cochlear implant. Many years later, highly effective, modern signal processing algorithms, e.g., continuous interleaved sampling (CIS), fine structure processing (FSP), and virtual channel processing, were first tested and developed with the aid of Ineraid patients fit with pedestals of the Utah design. Because for many years the Ineraid provided as high a level of speech understanding as that provided by other devices and because the percutaneous pedestal allowed the first testing of many modern signal processing algorithms, the Utah Artificial Ear project may be viewed as one of the most valuable research projects in the history of cochlear implants.

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.

Autologous human nasal epithelial cell sheet using temperature-responsive culture insert for transplantation after middle ear surgery.

Postoperative mucosal regeneration of the middle ear cavity and the mastoid cavity is of great importance after middle ear surgery. However, the epithelialization of the mucosa in the middle ear is retarded because chronic inflammation without epithelialization aggravates gas exchange and clinical function. These environmental conditions in the middle ear lead to postoperative retraction and adhesion of the newly-formed tympanic membrane. Therefore, if the mucosa on the exposed middle ear bone surface can be rapidly regenerated after surgery, the surgical treatments for cholesteatoma and adhesive middle ear disease can potentially be improved. In this study, we successfully generated a cell sheet designed for the postoperative treatment of cholesteatoma. We used nasal cells to create an artificial middle ear mucosal cell sheet with a three-dimensional (3D) configuration similar to that of the middle ear mucosa. The sheets consisted of multi-layered mucosal epithelia and lower connective tissue and were similar to normal middle ear mucosa. This result indicates that tissue-engineered mucosal cell sheets would be useful to minimize complications after surgical operations in the middle ear and future clinical applications are expected. Copyright © 2015 John Wiley & Sons, Ltd.

Development of the INERAID artificial ear.

Development of the INERAID artificial ear.

Sound pressure distribution within natural and artificial human ear canals: forward stimulation.

This work is part of a study of the interaction of sound pressure in the ear canal (EC) with tympanic membrane (TM) surface displacement. Sound pressures were measured with 0.5-2 mm spacing at three locations within the shortened natural EC or an artificial EC in human temporal bones: near the TM surface, within the tympanic ring plane, and in a plane transverse to the long axis of the EC. Sound pressure was also measured at 2-mm intervals along the long EC axis. The sound field is described well by the size and direction of planar sound pressure gradients, the location and orientation of standing-wave nodal lines, and the location of longitudinal standing waves along the EC axis. Standing-wave nodal lines perpendicular to the long EC axis are present on the TM surface >11-16 kHz in the natural or artificial EC. The range of sound pressures was larger in the tympanic ring plane than at the TM surface or in the transverse EC plane. Longitudinal standing-wave patterns were stretched. The tympanic-ring sound field is a useful approximation of the TM sound field, and the artificial EC approximates the natural EC.

Fabrication of low cost soft tissue prostheses with the desktop 3D printer.

Soft tissue prostheses such as artificial ear, eye and nose are widely used in the maxillofacial rehabilitation. In this report we demonstrate how to fabricate soft prostheses mold with a low cost desktop 3D printer. The fabrication method used is referred to as Scanning Printing Polishing Casting (SPPC). Firstly the anatomy is scanned with a 3D scanner, then a tissue casting mold is designed on computer and printed with a desktop 3D printer. Subsequently, a chemical polishing method is used to polish the casting mold by removing the staircase effect and acquiring a smooth surface. Finally, the last step is to cast medical grade silicone into the mold. After the silicone is cured, the fine soft prostheses can be removed from the mold. Utilizing the SPPC method, soft prostheses with smooth surface and complicated structure can be fabricated at a low cost. Accordingly, the total cost of fabricating ear prosthesis is about $30, which is much lower than the current soft prostheses fabrication methods.

In Vitro Efficacy of a Consumer-Marketed Ear Cleaning Tool

The WaxVac ear cleaning device may be a useful adjunct for patients requiring aural toilet. Cerumen removal and routine aural toilet is a common complaint that presents to the otolaryngology clinic. We tested this device to make an appropriate recommendation to our patients. We conducted in vitro testing of the WaxVac device on an artificial ear canal model and cadaveric temporal bones testing the strength of the suction, noise created by the device, and the ability of the device to remove foreign bodies from the external auditory canal. These foreign bodies included a PE tube, baby powder, a q-tip head, saline, and artificial cerumen. The WaxVac created very little suction as compared with Frazier tip suctions used in clinic. The device produced very little noise in the canal, which was equivalent to a #3 Frazier tip suction. The WaxVac was unable to remove q-tip heads or artificial cerumen from the ear canal model or the cadaveric temporal bones. Very little of the saline could be removed by the WaxVac, and only 20% to 50% of trials demonstrated removal of a PE tube. However, a large amount of the powder was able to be removed by the device. Although the concept of this device is good, the actual product does not produce adequate suction to remove cerumen or most common foreign bodies from the external auditory canal. It is unlikely to be useful for aural toilet.

Living Renal Transplantation for a Patient with an Artificial Ear Using Energy-Based Sealing Devices without Monopolar Electrocautery

Living Renal Transplantation for a Patient with an Artificial Ear Using Energy-Based Sealing Devices without Monopolar Electrocautery

Estimation of multiple sound source directions using artificial robot ears

Estimating the direction of a sound source is an important technique used in various engineering fields, including intelligent robots and surveillance systems. In a household where a user’s voice and noises emitted from electric appliances originate from arbitrary directions in 3-D space, robots need to recognize the directions of multiple sound sources in order to effectively interact with the user.This paper proposes an ear-based estimation (localization) system using two artificial robot ears, each consisting of a spiral-shaped pinna and two microphones, for application in humanoid robots. Four microphones are asymmetrically placed on the left and right sides of the head. The proposed localization algorithm is based on a spatially mapped generalized cross-correlation function which is transformed from the time domain to the space domain by using a measured inter-channel time difference map. For validation of the proposed localization method, two experiments (single- and multiple-source cases) were conducted using male speech. In the case of a single source, with the exception of laterally biased sources, the localization was achieved with an error of less than 10°. In a multiple-source environment, one source was fixed at the front side and the other source changed its direction; from the experimental results, the error rates on the localization of the fixed and varying sources are 0% and 36.9% respectively within an error bound of 15°.

Acoustic simulation of mobile phone coupled to artificial ear

Artificial ear is being used to evaluate the acoustic response and the sound quality of the mobile telephony devices, which simulates the practical listening condition of the outer ears. In this paper, a method to estimate the coupled acoustic response of the device with an artificial ear is studied to be effectively used in the design. To this end, an equivalent circuit model of the total receiver system including all accessory elements is established. Acoustic impedance of artificial ear, which is essential in the equivalent model, is directly measured by using three microphones arranged in tandem on the duct wall connected to the artificial ear. Input impedances of two artificial ears, Type 3.3 and 3.4, which are currently employed as the standard devices, are measured. The measured data is incorporated into the model to predict the acoustic response. To validate the proposed model using the measured impedance, the measured acoustic responses of two simulation systems including mobile phone and artificial ear are compared with the predicted ones. A reasonably good agreement between measurement and prediction is observed, and their difference is less than 4.5dB at the narrow communication band for a mobile phone (f<3.4kHz). It is also found that the input impedance of Type 3.3 ear is more robust to the change of measuring condition than Type 3.4 ear.

Test-Retest Reliability of Probe-Microphone Verification in Children Fitted with Open and Closed Hearing Aid Tips

To investigate the test-retest reliability of real-ear aided response (REAR) measures in open and closed hearing aid fittings in children using appropriate probe-microphone calibration techniques (stored equalization for open fittings and concurrent equalization for closed fittings). Probe-microphone measurements were completed for two mini-behind-the-ear (BTE) hearing aids which were coupled to the ear using open and closed eartips via thin (0.9 mm) tubing. Before probe-microphone testing, the gain of each of the test hearing aids was programmed using an artificial ear simulator (IEC 711) and a Knowles Electronic Manikin for Acoustic Research to match the National Acoustic Laboratories-Non-Linear, version 1 targets for one of two separate hearing loss configurations using an Audioscan Verifit. No further adjustments were made, and the same amplifier gain was used within each hearing aid across both eartip configurations and all participants. Probe-microphone testing included real-ear occluded response (REOR) and REAR measures using the Verifit's standard speech signal (the carrot passage) presented at 65 dB sound pressure level (SPL). Two repeated probe-microphone measures were made for each participant with the probe-tube and hearing aid removed and repositioned between each trial in order to assess intrasubject measurement variability. These procedures were repeated using both open and closed domes. Thirty-two children, ages ranging from 4 to 14 yr. The test-retest standard deviations for open and closed measures did not exceed 4 dB at any frequency. There was also no significant difference between the open (stored equalization) and closed (concurrent equalization) methods. Reliability was particularly similar in the high frequencies and was also quite similar to that reported in previous research. There was no correlation between reliability and age, suggesting high reliability across all ages evaluated. The findings from this study suggest that reliable probe-microphone measurements are obtainable on children 4 yr and older for both traditional unvented and open-canal hearing aid fittings. These data suggest that clinicians should not avoid fitting open technology to children as young as 4 y because of concerns regarding the reliability of verification techniques.

Numerical simulation of the human ear and the dynamic analysis of the middle ear sound transmission

Based on the clinical CT of normal right ear, a 3-D ?nite element (FE) model of the human ear consisting of the external ear canal, middle ear(tympanic membrane, ossicular chain, ligaments, tendons), and inner ear (including semicircular canals, vestibular, spiral cochlear)was constructed in this paper. The complicated structures and inner boundary conditions of middle ear were described in this model. Model analysis and acoustic-structure-?uid coupled dynamic frequency response analysis were conducted on the model. The validity of this model was confirmed by comparing the results with published experimental data. The amplitudes and velocities of tympanic membrane and stapes footplate, sound pressure gain across the middle ear, and the cochlear input impedance were derived. Besides, it was concluded that the ear canal can amplify the sound signal in low frequencies.The modes of vibration of middle ear auditory ossicles, oval window and round window have been analysed. This model can well simulate the acoustic behavior with the interaction of external ear, middle ear and inner ear, which can supply more valuable theoretical support for development and improvement of hearing-aid and artificial inner ear.

Implementation of a simplified, artificial external ear test fixture for measurement of the earplug induced auditory occlusion effect

Earplugs remain a frequently used short-term solution for occupational hearing conservation. Due to comfort limitations, as induced by, e.g., the occlusion effect, workers often only wear earplugs for limited amounts of time and are likely to develop professional hearing loss. The occlusion effect expresses itself in the low frequencies through an altered perception of the wearer’s own voice and the amplification of physiological noises that occur upon earplug insertion. While many studies examined the occlusion effect experimentally, no study was found that attempted to implement an artificial external ear model dedicated to the measurement of the objective occlusion effect. A simplified external ear test fixture can help to better assess and design earplugs, because it allows standardized experimental testing. This work describes the implementation of a cylindrical artificial test fixture of the human outer ear that comprises the auditory canal as well as the bony, cartilaginous, and skin tissues that are made up of rigid polyurethane foam and two different types of silicone, respectively. Obtained measurement results are compared to literature findings.

Comparison of direct measurement methods for headset noise exposure in the workplace

Specialized equipment and techniques are required to carry out direct sound measurements under occluded ears for the purpose of assessing the noise exposure from communication headsets. Standard ISO 11904 describes two procedures: (1) the microphone in a real ear (MIRE) and (2) the acoustic manikin technique using an occluded ear simulator IEC 60318-4. Methods using simpler artificial ears, such as IEC 60318-1, have also been proposed in occupational noise measurement standards such as CAN/CSA Z107.56. Such devices are more practical to use and more easily accessible. However, they have not been designed specifically for noise measurements under communication headsets and there is little comparative data to the manikin technique, which is considered the gold standard for simulated in-situ acoustic measurements. Furthermore, little is known about measurement reliability for the purpose of standardization. Fit-refit measurements were obtained under laboratory conditions with four different types of artificial ears (type 1, type 2, type 3.3, manikin), three communication headset types (circum-aural, supra-aural, intra-aural) and six different communication signals. Data was transformed into equivalent-diffuse sound levels using third-octave procedures as well as single number corrections. Results illustrate that methods using single number corrections as well as fit-refit standard deviations vary according to measurement conditions.

Hearing risk associated with the usage of personal listening devices among urban high school students in Malaysia

ObjectivesTo investigate listening habits and hearing risks associated with the use of personal listening devices among urban high school students in Malaysia. Study designCross-sectional, descriptive study. MethodsIn total, 177 personal listening device users (13–16 years old) were interviewed to elicit their listening habits (e.g. listening duration, volume setting) and symptoms of hearing loss. Their listening levels were also determined by asking them to set their usual listening volume on an Apple iPod TM playing a pre-selected song. The iPod's sound output was measured with an artificial ear connected to a sound level meter. Subjects also underwent pure tone audiometry to ascertain their hearing thresholds at standard frequencies (0.5–8 kHz) and extended high frequencies (9–16 kHz). ResultsThe mean measured listening level and listening duration for all subjects were 72.2 dBA and 1.2 h/day, respectively. Their self-reported listening levels were highly correlated with the measured levels (P < 0.001). Subjects who listened at higher volumes also tend to listen for longer durations (P = 0.012). Male subjects listened at a significantly higher volume than female subjects (P = 0.008). When sound exposure levels were compared with the recommended occupational noise exposure limit, 4.5% of subjects were found to be listening at levels which require mandatory hearing protection in the occupational setting. Hearing loss (≥25 dB hearing level at one or more standard test frequencies) was detected in 7.3% of subjects. Subjects' sound exposure levels from the devices were positively correlated with their hearing thresholds at two of the extended high frequencies (11.2 and 14 kHz), which could indicate an early stage of noise-induced hearing loss. ConclusionsAlthough the average high school student listened at safe levels, a small percentage of listeners were exposed to harmful sound levels. Preventive measures are needed to avoid permanent hearing damage in high-risk listeners.

J024021 鼓室換気能評価装置の開発([J024-02]音・光とバイオメカニクス)

Pneumatization of the middle ear cavity is associated with the transmucosal gas exchange function of the middle ear cavity and the eustachian tube function. In some cases, the tympanic membrane is gradually depressed by negative pressure of the middle ear cavity due to shortage of ventilation. As a result, the depressed tympanic membrane leads to adhesive otitis. Ventilation of tympanic cavity is important for medical treatments of adhesive otitis. The function of ventilation may be evaluated by measuring the volume of the middle ear cavity in addition to the eustachian tube function. In this research, the equipment for evaluating the function of ventilation in tympanic cavity was developed. In evaluation experiment of the equipment using an artificial ear model, the volumetric error of the ear model was 5% or less. In clinical measurement, the equipment was operated by medical doctors, and the volume of the middle ear cavity was able to be determined, and the function of the Eustachian tube was able to be evaluated.