People who are severely deaf or profoundly deaf have their hearing restored by Cochlear implants. Cochlear Implants are small, complex electronic device that provide a sense of sound to a person who is Profoundly deaf or severely deaf. The device contains external and internal components. Externally worn microphone, sound processor and transmitter system are responsible for collecting the stimuli it can be either sound or speech signal and internally implanted receiver and electrode system which receives signals from external system and send electrical currents to the inner ear. This helps the person with hearing loss to perceive the sound, understand speech, perception of environmental sounds and speech production.
He/she can either go for unilateral or bilateral cochlear implantation. This depends on the degree and type of hearing loss of an individual. Majority of them go for unilateral hearing and have advantages such as speech perception and able to perceive sounds. But later they start having issues like perception of speech in noise environments, localizing the sound source, speaking in a group setting which will have adverse effect on individual’s psychological status and reduced quality of life.
There are various advantages over unilateral hearing versus bilateral hearing. Bilateral hearing benefits are speech recognition in quiet, basic auditory needs are met, better speech perception in competing background noise and multiple speakers.
There are three beneficial advantages over monoaural hearing they are
Head shadow effect or better-ear listening head acts as a sound barrier, shelters the ear closest to the speech source from noise on the other side which improves speech comprehension. This effect has significant improvement if 4-7 db.
Binaural summation both ears receive identical signals improve speech perception.
Binaural squelch two ears allow for the spatial separation of signals and noise from competing sources. Below we see the comparison between unilateral versus bilateral hearing.
Studies reveals that benefits of bilateral cochlear implantation over unilateral cochlear implantation. They are
Speech perception in quiet
Speech perception in noise
Language development in children
Preverbal communication in children
Subjective benefits of hearing
Quality of life
It is known that listening with two ears allows people with normal hearing to understand speech better in background noise or in reverberant (echoing) environments. Binaural hearing also is an essential requirement for spatial hearing and sound localization. Most noise reduction and acoustical orientation abilities of the human auditory system crucially depend on the person having access to time, level, and spectral differences between the sound signals sensed by the two ears. In normal hearing, loudness summation occurs when switching from monaural hearing to binaural hearing, which will have an influence speech understanding. It has been shown in studies that loudness summation also occurs in bilateral cochlear implant users.
Studies have compared language development and speech perception of children with bimodal fitting (a cochlear implant in one ear and a hearing aid in the opposite ear) and bilateral cochlear implantation. Participants were children enrolled in the Longitudinal outcomes of Children with Hearing Impairment. Language development assessment was done at 3 years of age. Speech perception was evaluated at 5 years of age. This study found that language scores for children with bilateral implants were higher than those with bimodal fitting or those with unilateral implants.
Thus, proving that bilateral implantation is a better option both in adults and children with all the benefits mentioned above.
Team Bangalore Hearing and Implant Institute helps you in guiding your child’s journey of hearing if you are still in confusion with what to go for, is it one side or both sides? Do contact our team.