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Applications of spatial sound and related problems
Published in Bosun Xie, Spatial Sound, 2023
A cochlear implant is a treatment for severe-to-profound sensorineural hearing loss caused by cochlear lesions. It captures sound signals through a microphone, converts them into certain encoded electrical signals by signal processing devices, and stimulates the auditory nerve directly through the implanted electrode array to restore or reconstruct hearing. Bilateral cochlear implants may also be thought of as a special “binaural recording and reproduction” system. The electrode system, not the headphone, serves as the transducer in “reproduction.” Transducers display electrical signals rather than acoustic signals. Similar to the case of binaural hearing aids, bilateral cochlear implants (for patients with severe bilateral hearing loss) or unilateral cochlear implants combined with the residual hearing in the contralateral ear can restore or improve the ability of binaural hearing. However, bilateral cochlear implants also suffer from the problems caused by binaural hearing aids. More importantly, limited by technology, some simplification and approximation have been made in the signal processing strategy in artificial cochlea so that the temporal envelop information of sound is preserved and the final detail of sound is lost. Therefore, this signal processing strategy can preserve ILD information at most and lose low-frequency ITD information (Laback et al., 2015; Kan and Litovsky, 2015). However, further studies should be conducted to improve the performance of artificial cochlea in the rehabilitation of spatial auditory ability.
Flexible Electronic Technologies for Implantable Applications
Published in Muhammad Mustafa Hussain, Nazek El-Atab, Handbook of Flexible and Stretchable Electronics, 2019
Loss of any sensory organ of the body leads to several challenges in one’s life. Hearing loss is one such example where it can be either conductive, sensorineural, or a combination of both. The mechanism of hearing is through conduction of bones that transfer sound waves to the inner diaphragm and nerves translate these signals to the brain. Hearing loss can be due to age (presbycusis) which is a conductive loss as sound signals are not able to pass to the inner ear from the outer ear. The sound diminishing factors can be stiffening of the eardrum, thereby losing its elasticity, loss of mobility of conducting bones becoming rigid in their action. Whereas the damage of inner ear sensory hair cells or auditory nerve damage causes sensorineural deafness. For all such cases, cochlear implants are used externally for external applications. Preliminary work on a cochlear implant had begun in the 1960s, the first neural interface designed to revive the hearing for clinically deaf representing the first successful integration of stimulation electrodes within the peripheral nervous system (PNS) (Macherey and Carlyon 2014; Jalili et al. 2017). Cochlear implants are essentially used to bypass the sound signals from hair cells by inserting electrodes into the inner ear and directly stimulating the auditory nerve in response to the incoming audio signal from a microphone placed in the external ear area.
Medical device implants for neuromodulation
Published in Ze Zhang, Mahmoud Rouabhia, Simon E. Moulton, Conductive Polymers, 2018
The cochlear implant is the first example of a neural medical device that could substitute for a sensory body part, namely, the ear. A cochlear implant is an electronic device that provides the perception of sound to a person who is hard of hearing or deaf. In normal hearing, sound pressure waves travel down the ear canal, causing the eardrum to vibrate. The vibrations are transmitted to the cochlea by small bones of the middle ear, and these mechanical vibrations are transduced into action potentials that propagate to the brain, producing the perception of sound. The aim of a cochlear implant is to mimic the filtering normally performed by the bypassed portions of the auditory system. The cochlear implant dates to 1957, when Djourno and Eyriès evoked sound sensations in a deaf listener using an electrode implanted in the inner ear. Subsequently, the first commercialized multielectrode cochlear implant was implanted in 1978.
Using haptic stimulation to enhance auditory perception in hearing-impaired listeners
Published in Expert Review of Medical Devices, 2021
Over the past half a century, dramatic advances in hearing-assistive device technology have enabled it to transform the lives of people with hearing impairment. One prominent example is the cochlear implant (CI), which enables severely-to-profoundly hearing-impaired individuals to perceive sounds through electrical stimulation of the auditory nerve. The CI stands as one of modern medicine’s greatest achievements, allowing users to follow a conversation in a quiet environment with a similar accuracy to normal-hearing listeners [e.g. 1]. However, significant limitations to CIs remain, with users often having considerable difficulties locating and segregating sounds [2,3]. Similar issues are experienced by hearing aid users, though to a lesser extent [3,4]. These limitations lead to impaired threat detection and an inability to understand speech in noisy environments, such as schools, restaurants, and busy workplaces.
Developments in the human machine interface technologies and their applications: a review
Published in Journal of Medical Engineering & Technology, 2021
Harpreet Pal Singh, Parlad Kumar
Persons with an impaired sense of hearing are able to hear efficaciously using auditory substitution devices. By implementing the rough model of auditory substitution, the conceptual model of the retina which is connected to an inverse linear model of the cochlea with the aim to optimise the sensory substitution process is used as a prototype that comprises a progressive arrangement of computer connected to head-fixed camera and headphone by capturing the visual scene and converting it to auditory signals [174]. A cochlear implant is a surgically implanted electronic device placed into the cochlea to convert sound to electrical signals and is meant to provide the sense of sound to profoundly deaf persons specifically affected by the sensorineural hearing loss [175]. Persons with bilateral vestibular hypofunction find it difficult to walk in dim light and in irregular terrains owing to postural wobbling and unstable gait. The vestibular sensory substitution serves efficient brain and body coordination with high stability. The models of bilateral substitution systems are composed of integrated tactile, visual and proprioceptive systems that identify unique motion features and reduce or dispose of the magnitudes of defective features [176]. The main requirements of users of sensory substitution devices are light weight, small size, low power consumption, easy to use with high-performance customised functional settings incorporating high mobility [177]. In advanced virtual reality sensory devices, the tactile pin arrays are used to display the physical contact with the virtual environment by the non-visual approach [178]. HMI technology has opened up a new perspective on sensory substitution devices with the ability to assist and enable blind, deaf and mute people suffered by birth or after birth injuries and diseases to resume their affected capabilities of vision, hearing and speech partially or completely.
Modeling and simulation of cochlear perimodiolar electrode based on composite spring-mass model
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2022
Jianjun Li, Yue Wu, Jianye Zhuo, Zuo Wang
The cochlear implant is the most preferred method for the treatment of sensorineural hearing loss. It converts acoustic signals into electrical signals to directly stimulate the auditory nerve to improve the auditory function of the patient (Lenarz 2017). The perimodiolar electrode is a novel cochlear implant electrode device, which is pre-formed into a helix shape, with a guide wire inserted into the body to maintain the straightened state before surgery. This structure is then inserted into the human cochlea during the surgery as the guide wire is drawn out to restore its preset shape (Tykocinski et al. 2001). Although cochlear implant has been successfully used to restore the hearing of deaf people, it poses a risk of damage to the fragile structure of the cochlea during the electrode insertion. The electrode inserted into the cochlea is prone to yield and damage. Additionally, if the electrode is forcibly inserted while encountering resistance during the insertion process, it can damage the basilar membrane and destroy the residual hearing of the patient (Wardrop et al. 2005; Bas et al. 2016; Ramos-Macias et al. 2017; Ketterer et al. 2018). Therefore, highly qualified doctors are required for the application of the cochlear implant, who can quickly and accurately judge the insertion of the electrode array and skillfully operate surgical instruments during the surgery. This requires doctors to carry out extensive practice, actual combat, and reasonable pre-operative evaluation (Ma et al. 2017). In recent years, virtual reality technology has been widely used in the medical field, and various types of virtual surgery systems have been developed (Barber et al. 2018; Macmillan et al. 2018; Shono et al. 2018), which have played an important role in the training of doctors and in pre-operative evaluation. Combining cochlear perimodiolar electrode implantation surgery with virtual reality technology to realize a perimodiolar electrode inserted in the cochlea in a virtual environment can help doctors identify the optimal insertion path, preview the surgical process, and change the traditional model of designing surgical plans based on subjective experience. This process considerably improves the safety of the cochlear implant and reduces complications (Copson et al. 2017).