Audiological studies have proved that binaural listening has the following advantages: binaural listening can improve hearing by 5-10dB; better localization of sound sources and stereo sound perception; improved speech recognition in noisy environments; better auditory memory in binaural listening than in monaural, especially short-term memory; and improved communication and social skills of patients in daily life. Many studies have shown that bilaterally deaf patients can benefit greatly from wearing conventional HA on both sides of their ears. Bilateral CIs can also be implanted in bilaterally deaf children to improve their hearing. Bilateral CI implants have been tried since 1988, either because of technological innovations or because of poor hearing performance on the implanted side. In the 1990s, the purpose of bilateral CI implantation shifted to a desire to provide binaural gain, improve speech intelligibility in noisy environments, and obtain a better signal-to-noise ratio. 2004, Laszig reported that bilateral implantation accounted for 1% of the total number of CIs implanted, and bilateral CI implantation has become more common than ever. Recently, bilateral simultaneous CI implantation has become the mainstream trend, replacing the previous sequential (successive) CI bilateral implantation. The benefit of bilateral CI implantation to the patient is that it “guarantees optimal hearing performance after implantation”. The reason for this is the establishment of the advantages of binaural listening: 1. Elimination of the head shadow effect Different sound intensity is heard in both ears due to the different positions relative to the sound source. When the sound is emitted from the left side, the sound heard in the left ear is significantly louder than that heard in the right ear, which is known as the head shadow effect. Head shadow effect in the speech frequency range of binaural difference of 7dB, but in the high frequency of up to 20dB. due to binaural hearing, so that each ear are to obtain the appropriate signal-to-noise ratio, thus eliminating the head shadow effect. 2, retain the binaural sum effect binaural hearing at the same time when the sound will feel the sound louder, binaural hearing sum effect can be 3-5dB extra gain. 3, binaural static noise effect Bilateral listening can be through the presence of interaural time difference and interaural intensity difference, the central nervous system can improve the signal-to-noise ratio of about 3dB. 4, sound localization of the same sound source to reach the binaural existence of time difference between the two ears, this time difference between the two ears is very important for low-frequency hearing localization. The head shadow effect can form the sound intensity (energy spectrum) difference between the ears, which is very important for high-frequency hearing localization. The combined effect of the above time difference and spectral difference enables the listener to accurately determine the location of the sound source. 5, to avoid the unilateral CI implantation of hearing deprivation effect, such as bilateral deafness, only a single ear to give hearing aid compensation, the deaf ear is not given hearing aid compensation can be prolonged with time and degradation of function (this effect by Gelfand and Silman found in 1993). 6. Bilateral implantation stimulates the development of the central nervous system more rapidly than unilateral implantation. Unilateral cochlear implant recipients need to devote more attention and integrate more sensory systems when listening. In 2004, Kuhn-Inacker reported that in 39 cases of bilateral CI implantation in German prelingually deaf children, all children had better postoperative outcomes than unilaterally implanted children, with an average difference of 18.4% in speech recognition between bilaterally implanted and unilaterally implanted children, and concluded that although there was no significant correlation between postoperative outcome and age at the time of first implantation and time difference between two implantation sessions, it is recommended to implant the second CI at an early stage. other relevant studies reports such as Peters (2007), Wolfe (2007), Scherf (2007), and Galvin (2007) have reached similar conclusions. Summarizing the results of bilateral CI implantation studies, the following conclusions can be drawn: speech comprehension is enhanced in noisy environments, better signal-to-noise ratios are obtained by overcoming the head shadow effect; speech comprehension is enhanced in quiet environments; and sound localization ability is enhanced. Moreover, the study suggests that bilateral CI implantation should be performed at an early stage for better development of the auditory system and related systems. Feedback from children with bilateral CI implantation: “Now I can hear with both ears” “It’s very easy to use” “Now it’s easy to tell who’s talking to me” “If I play hide and seek, I know where to hide” “People don’t have to pay attention to which side of the table they have to sit on” These are the advantages of bilateral cochlear implantation, which are based on normal binaural listening. Because cochlear implants are ultimately artificial electronic devices that replace the hearing organs, they are not as natural as listening with your own ears, and there are some inconveniences in daily life. For example, there is a certain chance of malfunction (albeit low), maintenance, regular replacement of batteries or other accessories, a small number of restrictions on daily activities such as swimming, going out in rainy weather, strenuous exercise, etc. In addition, there are also important financial reasons, the above inconveniences will increase after bilateral implantation, and these issues should be taken into account by bilateral implantation patients to make a decision on the basis of weighing the advantages and disadvantages. In conclusion, the advantages are mainly based on the physiological function of hearing, while the shortcomings are mainly due to the deficiencies of cochlear implant electronic products that cannot be solved by the current technology itself when replacing the hearing organ.