Feasibility study on the evaluation of the effect of narrow-band CE- Chirp ASSR in the hearing fi eld after hearing aid in hearing- impaired children

The early intervention method for early detection of hearing-impaired children is to it the hearing aid. If the hearing aid is used for 3-6 months, the effect cannot meet the language development needs. The cochlear should be implanted as soon as possible. Therefore, it is important to accurately evaluate the hearing aid effect and choose the optimal intervention method in the early stage [1,2]. At present, the effect of hearing aids for hearing-impaired children is assessed by behavioral audiometry, but the results are affected by the intelligence level, coordination level, psychological status of the hearingimpaired children and the technical level of the inspectors [3,4]. Therefore, inding an effective objective assessment method for post-hearing rehabilitation is an urgent problem to be solved. Chirp ASSR is a technology that is induced by Chirp sound and incorporates multi-frequency sound and full spectrum detection engines. By simultaneously giving multiple frequencies of stimuli to both ears, and performing statistical Abstract


Introduction
The early intervention method for early detection of hearing-impaired children is to it the hearing aid. If the hearing aid is used for 3-6 months, the effect cannot meet the language development needs. The cochlear should be implanted as soon as possible. Therefore, it is important to accurately evaluate the hearing aid effect and choose the optimal intervention method in the early stage [1,2]. At present, the effect of hearing aids for hearing-impaired children is assessed by behavioral audiometry, but the results are affected by the intelligence level, coordination level, psychological status of the hearingimpaired children and the technical level of the inspectors [3,4]. Therefore, inding an effective objective assessment method for post-hearing rehabilitation is an urgent problem to be solved. Chirp ASSR is a technology that is induced by Chirp sound and incorporates multi-frequency sound and full spectrum detection engines. By simultaneously giving multiple frequencies of stimuli to both ears, and performing statistical analysis on the obtained multiple harmonics, the presence of ASSR is detected by the difference between harmonic frequencies and other frequencies. In this study, the narrowband CE-Chirp ASSR was used to test the response threshold of children with moderate, severe and severe hearing loss in the sound ield and the hearing threshold after behavioral audiometry. The test method was used to evaluate whether the hearing aid compensation effect was evaluated. This is important for selecting a precise rehabilitation strategy and assessing the rehabilitation effect after hearing aids.

Materials and Methods
Test subject 39 children with sensorineural hearing loss who were able to cooperate with behavioral audiometry with a full-digital behind-the-ear hearing aid (a total of 67 ears, grouped in ears), 22 males and 17 females, aged 2-7 years, the average age is 3.36±1.50 years old. Before the inclusion of the subject, the purpose and process of the experiment have been communicated to the guardian of the child and their consent has been obtained. The World Health Organization WHO-1997 stipulates that the average hearing at four frequencies of 0.5, 1, 2, and 4 kHz is 41-60 dB HL for moderate hearing loss, 61-80 dB HL for severe hearing loss, and >80 dB HL for severe hearing loss. Subjects were divided into moderate hearing loss group, severe hearing loss group and very severe hearing loss group according to this standard. All subjects tested the narrow-band CE-Chirp ASSR and behavioral audiometry under the sound ield. The test sequence was based on random principle. The narrow-band CE-Chirp ASSR under the sound ield was set as the experimental group. The hearingdetection behavior of the hearing-impaired children in this group was the control group.

Test steps and methods
Medical history collection: Hearing screening of newborns, time of hearing aid intervention, situation of language training and rehabilitation, history of otitis media, family history of deafness, and exclusion of children with hearing impairment such as mental and intellectual abnormalities.

Conventional otology examination:
The external auditory canal and tympanic membrane were examined to con irm that the subject had no abnormalities in the external auditory canal that the tympanic membrane was intact and the marking was clear.

Acoustic impedance test:
Check the bilateral tympanogram is "A" type.
Otoacoustic emission: All subjects underwent otoacoustic emission examination to exclude post-cochlear lesions.

Sound ield calibration:
Behavioral audiometry is performed in a standard soundproof room using GSI's Audiostar Pro audiometer and ER-3A insert earphones. Sound ield setting: the angle between the speaker and the sagittal plane of the subject is 45°, the center of the speaker is aligned with the external auditory canal, the distance is 1m and at the same horizontal plane. The sound ield calibration is based on the national standard GB/T4854.7-2008, and the unit is dB HL. The narrow-band CE-Chirp ASSR under the sound ield uses the Danish International Hearing Company Eclipse 25 objective hearing test platform, record the narrow-band CE-Chirp stimuli (stimulus rate 90Hz) of 0.5, 1, 2, 4 kHz in the ASSR test system with a sound card and import it into the "Huier Hearing Test Software", connect the ampli ier and speakers. Sound ield setting: The speaker is facing the subject's head, at an angle of 0° to the subject's lying position, at a distance of 0.6 m and at the same level. The sound system tests the hearing impaired subject for biological calibration during the development phase, and the electroacoustic engineer calibrates the sensor (speaker) in dB HL.
Behavioral audiometry: Con irm that the hearing aid is working properly before the test and the frequency shift noise reduction function is not turned on. Test ear wear hearing aid, opposite ear plus sponge anti-noise earplugs. Select visual reinforcement or game audiometry based on the subject's age and behavioral ability, establish conditionalization, and ensure that the rules are fully understood and the test begins. The minimum intensity of more than two reliable responses is de ined as the hearing threshold, and the hearing threshold of 0.5, 1, 2, 4 kHz is obtained. Remove the hearing aid for 30 minutes, and then use the insert earphone to measure the bare ear threshold of 0.5, 1, 2, 4 kHz.

Narrow-band CE-Chirp ASSR test under sound ield:
The test is carried out in an electromagnetic shielding room. The sleep deprivation method allows the hearing-impaired child to enter a natural sleep state, and 10% chloral hydrate (0.5 ml/kg) is orally administered to a hearing-impaired child who cannot sleep well. The recording electrode is placed in the middle of the forehead close to the hairline, the ground electrode is placed at the base of the nose, and the reference electrode is placed in the left and right mastoids. The impedance of all electrodes is <5kΩ, the impedance between the electrodes is <3kΩ, the stimulation frequency is 90Hz, and the artifact rejection level is ±40μV. Using the singleear single-frequency test, the "Huier Hearing Test Software" gives the narrow-band CE-Chirp stimuli of each frequency through the speaker, and the tested ear wears the hearing aid (the settings of the hearing aid are the same as those of the behavioral listening), and the opposite ear add sponge antinoise earplugs, use the 5 to 10 method to ind the post-hearing response threshold for each frequency.

Statistical method:
The paired sample T-test was used for the data of SPSS19.0 software. P<0.05 was considered statistically signi icant.

Moderate hearing loss group uses the experimental group and the control group test method to evaluate the hearing aid compensation effect
It can be seen from table 1 that there is no signi icant difference in the test results of the experimental group and the control group with moderate hearing loss at 0.5, 1, 2, and 4 kHz (P=0.317, 0.111, 0.052, 0.511, P>0.05). The application of the narrow-band CE-Chirp ASSR in the sound ield to evaluate the hearing aid compensation effect of children with moderate hearing loss can achieve the same accuracy as behavioral audiometry at 0.5, 1, 2, 4 kHz.

Severe hearing loss group uses the experimental group and the control group test method to evaluate the hearing aid compensation effect
It can be seen from table 2 that there is no signi icant difference in the 0.5, 1, 2 kHz between the experimental group and the control group of children with severe hearing loss (P=0.755, 0.484, 0.311, P>0.05), and there is a signi icant difference at 4 kHz (P=0.002, P<0.05), mean difference is -6.4dB HL. The application of the narrow-band CE-Chirp ASSR in the sound ield to assess the hearing aid compensation effect of children with severe hearing loss can achieve the same accuracy as behavioral audiometry at 0.5, 1, 2 kHz, and the correction value needs to be applied at 4 kHz.

Extremely severe hearing loss group uses the experimental group and the control group test method to evaluate the hearing aid compensation effect
It can be seen from table 3 that there is no signi icant difference in the test results of the experimental group and the control group of children with extremely severe hearing loss at 0.5, 1, 2, and 4 kHz (P=0.368, 0.538, 0.102, 0.509, P>0.05). The application of the narrow-band CE-Chirp ASSR in the sound ield to evaluate the hearing aid compensation effect of children with extremely severe hearing loss can achieve the same accuracy as behavioral audiometry at 0.5, 1, 2, 4 kHz.
When the degree of hearing loss was not grouped, the experimental group and the control group test method evaluate the hearing aid compensation effect As can be seen from table 4, there was no signi icant difference between the experimental group and the control group at 0.5, 1, 2 kHz (P=0.230, 0.623, 0.376, P>0.05), and there was a signi icant difference at 4 kHz (P=0.010, P<0.05). The mean difference is -3.2dB HL. It is indicated that the narrow-band CE-Chirp ASSR and the behavioral audiometry difference in the sound ield of children with different hearing loss levels are different, and need to be researched and applied in groups, especially 4 kHz.

Development and clinical application of Chirp stimulation
Chirp stimulation is also called chirped pulse sound. The phase characteristic is that the low-frequency sound is emitted early, and the high-frequency sound is emitted late, so that more nerve ibers are synchronously discharged, increasing the reaction speed and amplitude, and shortening     the detection time [5][6][7]. With the development of Chirp stimulation signals, Chirp ASSR has been widely used in China [8]. A number of studies [9][10][11][12][13] show that narrow-band CE-Chirp ASSR has good accuracy and reliability in objective hearing evaluation. The narrow-band CE-Chirp used in this study is to decompose the wide-band CE-Chirp sound into four frequency components centered at 0.5, 1, 2, and 4 kHz, and has good frequency speci icity. At the same time, the synchronizing of the auditory nerve caused by the delayed wave motion of the cochlea is overcome. The waveform is shown in igure 1.

Narrowband CE-Chirp ASSR under sound fi eld
The Eclipse 25 objective hearing test platform used in this experiment works on the principle of detecting the phase and amplitude values of the irst 6-8 harmonics from the changing biological noise and noise loor, and analyzing the 90 Hz fundamental harmonics and higher harmonics such as 180Hz, 270 Hz, etc. The response amplitude at the 90 Hz fundamental harmonic is the highest. As the number of harmonics increases, the response amplitude decreases. Compared with the single sample test method in which the traditional ASSR only analyzes the irst harmonic, this new analysis method can improve the signal-to-noise ratio and obtain more optimized results [14]. Current research suggests that the origin of ASSR is related to the modulation frequency. When the stimulation rate is higher than 70 Hz, the ASSR is a steady-state response from the brainstem, which is unaffected by attention, arousal, and sleep [15]. In this study, the 90Hz stimulation rate was used, and the acoustic ampli ication of the hearing aid was uploaded to the brainstem [16], which laid the theoretical foundation for nerve conduction in the ASSR test under the sound ield.
The experimental subjects were 39 hearing-impaired children with good auditory response, good rehabilitation effect and good performance of behavioral audiometry. The results obtained by the matching test are analogized to the evaluation of the hearing aid compensation effect of hearingimpaired children who cannot cooperate with behavioral audiometry. For hearing-impaired children who can obtain behavioral audiometry results, the electrophysiological threshold test results after hearing aids are obtained, and the subjective and objective test results are mutually veri ied, which has more scienti ic guiding signi icance [17].
Previous studies have pointed out that the ASSR lowfrequency response correlation is worse than the highfrequency, which is presumed to be due to the fact that the hair cell and basement membrane near the volute are more synchronic than the volute, and the ASSR amplitude of the low-frequency signal is lower than the higher frequency signal [18,19], or the subject can't completely relax or go to sleep in a short time, it is dif icult to get a higher signal to noise ratio, which has the greatest impact on the low frequency. There were no signi icant differences between the experimental group and the control group in the low frequency of children with different hearing loss in this experiment. Probably because the subjects are in deep sleep state when testing the narrow-band CE-Chirp ASSR under the sound ield, the EEG interference is small and the signal-to-noise ratio is high. During the test, the subject sometimes has sudden awakening or EEG interference. At this point, the test should be suspended, and the test should be repeated after it falls asleep again. The hearing-impaired child who cannot enter deep sleep again will be tested again within one week.
The results of this experiment should pay attention to the following problems in clinical application: 1. The hearing aid turns off the frequency shift noise reduction function in advance, otherwise it may affect the test result. 2. Exclusion of the ASSR electrophysiological response threshold and hearingimpaired children with mental and intellectual abnormalities in the bare ear, children with hearing impairment who have severe hearing loss or other developmental abnormalities should carefully use the narrow-band CE-Chirp ASSR in the sound ield to evaluate the hearing aid compensation effect. 3. The results of this experiment are applicable to children with sensorineural hearing loss. It is not clear whether it is suitable for hearing-impaired children with middle ear lesions and posterior fossa lesions. 4. The conditions and layout of electromagnetic shielding rooms in different hearing centers are different. It is recommended to establish corresponding correction values for each hearing center to play a better guiding role in clinical application.
In summary, the narrow-band CE-Chirp ASSR under the sound ield has clinical application value as an objective hearing aid evaluation method. For young children with moderate, severe and extremely severe sensorineural hearing loss, the application is based on the degree of hearing loss, children with severe hearing loss apply correction values at 4 kHz, and children with moderate and extremely severe hearing loss do not need to apply correction values. It can achieve the same accuracy as behavioral audiometry, and can timely understand the compensation effect and functional status of hearing aids for hearing-impaired children, and help hearing-impaired children to choose the optimal intervention strategy to obtain the best rehabilitation effect.

Outlook
The single-ear single-frequency test method of this experiment takes a long time and the ef iciency is not high enough. If you can explore a multi-frequency sound mode under the sound ield, improve the test ef iciency and shorten the test time, it is more conducive to clinical application. In addition, children with special hearing loss need to turn on the frequency shift function of the hearing aid. If we can study whether the narrow-band CE-Chirp ASSR in the sound ield can effectively evaluate the digital hearing aids with the frequency shifting function enabled, it can greatly help this part of the hearing-impaired children.