A Study On The Tone Perception And Output Of Children With Cochlear Implants In A Noisy Environment

In Mandarin speech recognition and expression,tone plays an important role.For children with cochlear implants,tone is the key to language learning.Previous studies have mainly focused on the perception or output in a quiet environment,but most of the daily life is in a noisy environment.The results of the research in a quiet environment cannot represent the true speech level of cochlear implants in daily life.The language ability is reflected in two aspects: listening and speaking.Therefore,to fully understand the tone control of children with cochlear implants,it is necessary to conduct a comprehensive investigation of their tone perception ability and vocalization ability in a noisy environment.This article recruited children with cochlear implants(CIs)aged 5 to 6 years old and normal hearing children(NHs)of the same age to study their characteristics of tone perception and production in a noisy environment.In the perception experiment,the perception environment was a quiet environment and three noise environments(-5d B SNR,0d B SNR,and 5d B SNR).The ability of the two groups of participants to identify tones was investigated.The main results of the perception experiment are as follows:1.The results of the tone perception experiment show that no matter what the perception environment is,the cognition ability of CIs is significantly weaker than NHs.Even in a quiet environment,the tone recognition of CIs can reach 96.245%,but there is still a significant gap with hearing children(99.855%).2.Comparing the perception results in different environments,it is found that the anti noise interference ability of CIs is weaker than that of the same age NHs.The lower the noise signal-to-noise ratio is,the more obvious the interference effect is.The tone recognition rate of CIs can reach 96.245% in quiet environment.With the decrease of SNR,the tone recognition rate decreases from 96.245% in quiet environment,96.789% in 5d B SNR,93.312% in 0d B SNR and 81.225% in-5d B SNR.However,the recognition rate of NHs is 99.855% in quiet environment,and it can still reach 97.186% in-5d B SNR noise.3.Comparing the recognition difficulty of different tones,it is found that the recognition difficulty order of CIs is similar to that of NHs.Regardless of the perception environment,it is difficult to recognize T2 and T3,and it is easier to recognize T2 and T4.In addition,by comparing with the previous research on tone recognition with the same duration,it is found that the tone duration is an important clue: when the duration is balanced,T4 will be the most difficult to recognize;when the duration of the tone is retained,T4 is the easiest to recognize.In the output experiment,the communicative background is a quiet environment and three noise environments(-5d B SNR,0d B SNR,and 5d B SNR).The tone output of CIs and NHs is analyzed.System analysis is based on extracting two fundamental parameters(F0 curve,F0?mean,F0?min,F0?max,F0?range)and duration.The main findings are as follows:1.Observing the F0 curve in quiet environment,it is found that CIs has basically mastered the four tone modulation characteristics,i.e.T1 high level,T2 rising,T3 zigzag,T4 falling.There was no significant difference between F0 and NHs.3.Observing the F0 curve under the noise environment,it is found that the tone output of CIs is seriously disturbed by the noise.When the signal-to-noise ratio drops to-5d B SNR,the four tone feature disappears,and the F0 curve is gentle and has the trend of coincidence with each other.Moreover,in the noise environment,the F0 mean value of CIs is lower than that of NHs,especially when 5d B SNR and-5d B SNR are significant.2.Comparing the F0 mean of the two groups,we found that the auditory feedback mechanism of CIs was abnormal.When the SNR is reduced to-5d B SNR,the F0 mean value of NHs is significantly higher than that in quiet environment,which shows that NHs has a good auditory feedback mechanism.After noise concealing sound is found,the communication strategy to improve F0 is successfully implemented.However,no F0 improvement was found in CI.4.Comparing the duration length of the two groups of subjects,we found that although CI spoke slowly,the relative characteristics of the duration length of the four tones were similar to that of NHs: T3 tone was the longest,T4 tone was the shortest.In addition to T4,the duration of CIs was significantly longer than that of NHs.This may indicate that the shortest duration is the significant identification of CIs to T4.5.Comparing different output environments,CI and NHs showed Lombard effect.NHs shows that the lower the SNR is,the higher F0 is;CI shows that the lower the SNR is,the longer the duration is.Compared with the quiet environment,the duration of NHs in the noise environment has no significant change,but the F0 mean value in-5d B SNR is significantly higher than that in the quiet environment.Therefore,CI adopts the strategy of increasing duration in noisy environment,while NHs prefers to adopt the strategy of increasing F0.