The goal of hearing aid fitting is to provide the maximum possible speech stimulation to the infant and child with a hearing aid that is within the safe and comfortable hearing range; that is, the amplified speech should be above the infant’s perceptual threshold but below the discomfort threshold for the full range of speech frequencies in both ears. For the above purpose, the following basic process should be followed in the process of hearing aid fitting. 1. Hearing aid selection ① For those who are diagnosed with residual hearing, choose the appropriate power hearing aid according to the residual hearing of each frequency. If the ABR result is only low frequency residual hearing or low, medium or high frequency hearing, the subjective and objective examination does not lead to a response (at this time, ASSR test should be conducted, the result has great reference value), you should not give up the hearing aid fitting, but should complete the missing frequency point value according to the eHL value corresponding to the loudest output intensity +5dB of the ABR test instrument to obtain the hearing curve and use it as a temporary basis for the first fitting of extra high power The hearing curve should be used as a provisional basis for the initial fitting of the hearing aid. At the same time, it is important to obtain the results of the auditory behavior assessment after the hearing aid, which can be used for the subsequent precise adjustment of the hearing aid. Since infants learn language by listening to speech sounds, it is important to ensure that the electroacoustic properties of the hearing aids meet the high requirements for speech intelligibility and the evaluation of the overall effect of the hearing aid. Therefore, it is important to choose a high quality, fully digital hearing aid with high adjustment sensitivity, reliable performance and quality (high fidelity, wide band gain, directional microphone and digital noise reduction are necessary to avoid distortion of speech signal amplification and speech recognition difficulties) as much as possible, so that the acoustic gain of each fine frequency band, the digital processing of sound and the maximum output can be fully adjusted within 3-6 months after the initial fitting. and maximum output parameters. 2.Pre-adjustment of hearing aids Before the use of hearing aids, the fitter should test the selected hearing aids, and if possible, use the real ear measurement technology to first test the performance index of the hearing aids and compensate for the actual needs of the patients by adjusting the insertion gain at different frequencies, while monitoring the sound pressure level of the output to the ear canal so that it does not exceed the loudness discomfort level of the patients, so as to achieve individualized and objective fitting. (1) For infants and children less than 6 months old, hearing loss results (especially tb-ABR results) for the corresponding frequency characteristics can be obtained only by electrophysiological response threshold measurements, thus guiding the hearing aid pre-tuning. Hearing aid gain and maximum output tuning should be done conservatively by dropping 5 dB from the estimated value for the first time and later adjusted according to the behavioral response reports observed after the hearing aid (which generally refers to the need to increase the gain or not). Obtain the behavioral response after hearing aid as early as possible and instruct them to provide timely feedback after hearing aid or follow-up consultation within 1-2 weeks during the initial fitting. At the same time, parents should be carefully instructed to complete the auditory behavior observation report after hearing aid fitting for infants and children for further adjustment of hearing aid, and then provide feedback after hearing aid for follow-up consultation every 2-4 weeks until the follow-up interval can be gradually extended after six months. (2) For infants and younger children aged 6-36 months, physiological tests should be performed in conjunction with behavioral response audiometry to determine the degree of hearing loss and hearing configuration and to guide hearing aid pre-tuning. Obtaining the hearing aid threshold early (with full parental involvement) is particularly important for evaluating the pre-tuning and fine-tuning of the hearing aid session, with feedback or a follow-up visit within 1-2 weeks after the hearing aid, and determining the subsequent follow-up observation protocol; speech assessment should be performed as early as possible, otherwise as in infants and toddlers 3-6 months of age. (3) In hearing aid pre-conditioning, the acquisition of the target curve depends on the chosen fitting prescription formula to calculate the target values of gain, output and compression ratio for each frequency of the hearing aid. Therefore, the fitter should have a full understanding of the fitting formula used for the chosen hearing aid, realizing that many of these formulas and algorithms are for adults and should be different for people with different hearing loss; the application should be flexible according to the daily auditory behavioral responses observed in infants and young children after hearing aids and accumulated experience. The directional microphone technique does improve speech recognition in noisy environments, especially when both speech and noise are located in front of the child. However, infants learn speech by listening to adults around them, and it is possible that the child will not be directly in front of the speaker, so directional microphones are inappropriate for infants and may reduce their opportunities to learn speech. However, whether the directional microphone is turned on or off depends on the child’s living environment, speech and language, behavior, and the willingness of the parent or caregiver to help the child change the microphone mode by switching it on and off when the environment changes (if the child is not very aware of active communication, it is generally recommended that the directional microphone not be turned on). The age at which directional microphones are appropriate for children is inconclusive, but some studies suggest that directional microphones are an option for children over the age of 5. The process of fine adjustment of the hearing aid is particularly important for infants and children. Feedback should be given every 2-3 weeks during the initial period of fine tuning to observe auditory behavior and speech responses after the hearing aid, and every 3 months for 1 year after the hearing aid is fine-tuned, and then every 6 months or year thereafter, and parents should be instructed on how to observe the infant’s response to sound. The audiologist and parents should realize that the fitting and evaluation of hearing aids for infants and children is a gradual and precise process, and they should be more patient. (4) Use of hearing aids and eardrums Use soft eardrums as much as possible, pay attention to the influence of eardrums on the acoustic characteristics of hearing aids, and ask the parents to observe the feedback whistling at all times. The feedback management function should be turned on during commissioning, but it is important to understand that the effect of feedback suppression is limited and should not be over-relied on. To ensure that the eardrum has a good seal, the eardrum should be replaced regularly. Parents should be advised not to force the child to use the hearing aid when he or she cries more frequently or refuses to wear it, but to find the cause (probably due to over-amplification) and to contact the fitter or follow up in a timely manner. In addition, parents are cautioned to check the hearing aid immediately and to follow up with the doctor as soon as possible if they notice abnormal auditory behavior in children, such as dulling of the response to sound (concern about the large vestibular canal syndrome). 3.Fitting and effect evaluation of hearing aids The effect evaluation of hearing aid fitting is of great significance to the clinical dispenser and parents. Through the results of the effect evaluation, we can understand the degree of improvement in learning, speech and language development and behavioral cognitive ability of the child after using the hearing aid, so as to judge whether the hearing aid is ideal and optimal. The assessment of the effectiveness of hearing aids for infants and children should be based on the age, cognitive level and behavioral ability of the child. 4. Regular monitoring of hearing aid performance and hearing aid performance The performance of hearing aids for children and their effects should be monitored regularly and adhered to for a long time. Long-term monitoring should include audiological evaluation, electroacoustics of hearing aids, real ear, and hearing aid function tests, and should also include continuous evaluation of the hearing dormitory boy’s ability to interact, level of neurological or emotional development, level of cognitive development, and level of academic development, to ensure that the progress obtained by the child is comparable to his or her ability.