It is essential to those with hearing loss that sound is a huge factor and that they can hear. It is personal, challenging and different for everyone. Due to lack of funding hearing aids and cochlear implants are not heavily researched or well educated. To be qualified to get either hearing aids or cochlear implants, a person must have either conductive hearing loss or sensorineural hearing loss. A conductive hearing loss is when there is a problem for sound waves to reach the outer ear, tympanic membrane, or middle ear. A sensorineural hearing loss is the loss of inner hair cell and outer hair cell function, reduced electrical potential and changes to the mechanical properties of the cochlea. Sensorineural hearing loss ranges from minor to profound hearing loss. People with these hearing deficits have to figure out what kind of hearing devices he or she will need. Patients will have to learn about sound, the technology, the types of devices and how it will affect them developmentally. From a functional, medical, technological, and developmental perspective, hearing aids and cochlear implants have both benefits and safety risks.
Like fingerprints, sound is personal and unique for everyone. One person may be able to hear higher frequencies than someone else. To one person, a bell ringing can sound like a buzzing to someone else. For those who are partially or entirely deaf, some sounds are unfamiliar. Hearing aids and cochlear implants make it easier for those with hearing loss to communicate better and be more engaged with their environment. It is important that patients know how a hearing aid or cochlear implant functions. Hearing aids are better for patients who have minor to moderate hearing loss. They amplify weak sounds more than intense, loud sounds. In an article by Harvey Dillion, he explains that hearing aids act as a collection of functional building blocks. A signal passes through these blocks to a microphone, amplifier, a filter, and a receiver. This signal can come from a telecoil, a radio receiver, or direct audio input which converts electromagnetic and magnetic waves to voltage. The microphones improve the signal-to-noise ratio and intelligibility of speech by several decibels. The amplifier acts as a card reader or scanner. Each signal represents a string of numbers which affects the size and nature of the signal. The circuits in the amplifiers are specially constructed to process sounds for each device, which has specific software loaded on to it. The filter changes the amplitude in the signal and functions as tone controls. The filter can be used to break the signal into frequency ranges that are suitable to the patient. The receivers convert the electrical signals back into sound. The frequency or sound responses are based on peaks and troughs caused by the resonances in the receivers and a damper. The damper smooths out the peaks and troughs, which improves sound quality and comfort levels. Cochlear implants function similar to hearing aids in two parts. They are better for those who have severe to profound hearing loss. First is the internal parts which are implanted by surgery. The internal parts are 12 to 22 electrodes implanted along the cochlea. They are 2cm long. Each electrode contact are located near auditory nerve fibers that code for different frequencies or sounds. The second part is the external part which captures the sound with one or several microphones and converts it into a stimulation code with a speech processor. The stimulation code transmits the internal part through a radio frequency link. The radio frequency links are coils consisted of the external transmitter and internal receiver. The external transmitter and internal receiver are held in place across the skin with magnets. The receiver decodes radio-frequency signals and sends stimulation currents to the electrodes. Rather than receiving sound, the cochlear implant mimics the filtering performed by the auditory system. Similar to the hearing aid, the sound passes to the microphone and the filters. The number of filters is equal to the number of electrodes. The filters break down the sound to several frequency ranges, similar to an equalizer of a Hi-Fi audio system. This step is mimicking the function of the basilar membrane which disperses sounds. The envelope of the filter’s output is extracted, mimicking the behavior of hair cells. Finally, the envelopes modulate the amplitude of electrical pulses that are directed to one of the electrodes. Looks simple, yet complicated cochlear implants and hearing aids have the same purpose.