M.Sc. in Medical Engineering Artificial Bionic Ear Hassanain Ali M.Sc. in Medical Engineering

EAR considers the most communicating Organ for the Human Beings.

Human Ear is divided Outer Ear, Middle Ear and Inner Ear. into three sections ; Outer Ear, Middle Ear and Inner Ear. Each section plays an important and a unique part in decomposing and translating acoustical waves into electrical impulse signals that are used by the Brain.

Sound waves travel through the Pinna along the external canal of the Outer Ear and cause the Tympanic Membrane (Ear Drum) to vibrate, then this motion is transferred to the Middle Ear. The Stapes (Stirrup) is connected to the ear drum by the other middle ear bones, the Incus (Anvil) and the Malleus (Hammer). A difference in the pressure causes the stapes to move and it stimulates the perception of sound. The three bones carry the vibrations to the Cochlea of the Inner Ear.

Ossicles of the Middle Ear

Sensory Organ of Hearing. Cochlea is composed of three The Cochlea is the part of the Inner Ear where mechanical motion of the auditory vibration is converted to electrical impulses, so it considers the Sensory Organ of Hearing. Cochlea is composed of three fluid filled chambers that extend along the length of the structure and help to maintain the Body Balance. The cochlear duct contains the Basilar Membrane upon which lies the Organ of Corti. This organ has ten thousands of sensory Hair Cells which are connected to the nerve endings of the Auditory Nerve.

efferent signals ( from both ears ) Hearing Mechanism efferent signals ( from both ears ) Middle Ear Ossicles other Ear Sound efferent signals Fast Open Hair Cells Loop

cross section of the Cochlea Structure of Cochlea Three main chambers: Scala Vestibuli Scala Media Scala Tympani cross section of the Cochlea

Function of Cochlea Organ of Corti

Hearing Loss is divided primarily into Hearing Loss can be rated on a scale based on the threshold of hearing. Severe hearing loss is defined as a bilateral hearing threshold of 70-90 dB and profound hearing is defined as a hearing threshold of 90 dB and above. Hearing Loss is divided primarily into two general categories: Conductive and Sensorineural.

Conductive hearing loss results from diseases or disorders that limit the transmission of sound through the outer or middle ear. This loss can usually be treated medically or surgically. In some cases, a hearing aid can provide sufficient hearing improvement. Sensorineural hearing loss affects the auditory nerve and hair cells inside the cochlea that excite it. In this case, sound is transmitted normally through the outer and middle ears, but the inner ear is less efficient in transmitting the sound. The result is an impaired ability to hear sound and to understand speech. This loss is usually treated with a cochlear implant which amplifies sound to overcome the decrease in sensitivity of the fine nerve endings within the cochlea.

Sensorineural Conductive Otosclerosis = Stiff Ossicles Damaged Hair Cells Wax Torn Eardrum Otitis Media = Fluid in middle ear Damaged Nerve

Healthy Cochlea

Damaged Cochlea

bypasses damaged parts of The Bionic Ear bypasses damaged parts of the inner ear and electronically stimulates the nerve of hearing that converts sound into electrical impulses. Part of the device is surgically implanted in the Skull behind the ear and tiny wires are inserted into the cochlea. The other part of the device is external, and battery powered.

All devices have the following features in common : Cochlear Implant is a type of neural prosthetic device that can restore the lost hearing sensation for the severe hearing disabled and profound deaf. All devices have the following features in common : A microphone that picks up the sound, A speech processor that converts the sound into electrical signal, A transmission system that transmits the electrical signals to the implanted electrodes with transcutaneous RF link, And an intra-cochlear electrodes array that is inserted in the cochlea by surgery.

Cochlea Implant Components The hearing process with using a bionic ear can be summarized as follows ;

1- Sounds are detected by the Microphone. 2- The information from the microphone is sent to the Speech Processor. 3- The speech processor analyses the information and converts it into an electrical code. 4- The coded signal travels via a cable to the transmitting coil in the headset. Radio waves from the transmitter coil carry the coded signal through the skin to the implant inside. 5- The implant package decodes the signal. This signal contains information that determines how much electrical current will be sent to the different electrodes array. 6- The appropriate amount of electrical current passes down the appropriate lead wire to the chosen electrodes. 7- The position of stimulating electrodes within the cochlea will determine the frequency of the sounds. The amount of electrical current will determine the loudness of the sounds. 8- Once the nerve endings in the cochlea are stimulated, the message is sent up to the Brain along the auditory nerve. The Brain can then try to interpret the stimulation as a meaningful sound.

Electrodes Array Electrodes Array is inserted in the cochlea so that different auditory nerve fibers can be stimulated at different places. Electrodes stimulation is depending on the signal frequency. Electrodes near the base of cochlea are stimulated with high frequency signals, while electrodes near the apex are stimulated with low frequency signals.

The signal processing strategy consists of band pass filters that divide the acoustic wave into four channels. The envelopes of the band-passed waveforms are then detected by rectification and low pass filtering. The generated pulses are delivered to the appropriate electrodes through a radio frequency link.

Components of Bionic Ear

For centuries, people believed that only a miracle could restore hearing to the Deaf. It was not until fifty years ago that scientists first attempted to restore normal hearing to the deaf by electrical stimulation of the impaired auditory nerve.

M.Sc. in Medical Engineering Artificial Bionic Ear Hassanain Ali M.Sc. in Medical Engineering