Objective To investigate the effects of long-term occupational exposure to high-frequency noise in specific frequency bands on auditory function of the inner ear,and to evaluate the mechanisms of auditory threshold damages due to high-frequency noise exposure utilizing bone conduction audiometry and acoustic physical models.Methods The study subjects included factory workers and airport ground staff working in high-noise environments for a long period.Two groups(an exposure group and a control group)were established,and the exposure group was further divided into 3 subgroups according to exposure duration:5-9 years,10-14 years,and over 15 years.Bone conduction audiometry was used to assess auditory threshold changes in different frequency bands(4,6,8 kHz),while a sound level meter was employed to record noise exposure intensity.The impact of noise on the cochlea was simulated using an acoustic physical model.Multivariable regression analysis,controlling for confounding factors such as age and gender,was used to further analyze the independent effects of exposure duration and intensity on auditory damage.Results The auditory thresholds of exposure group were significantly higher than those of control group in the high-frequency bands,particularly in 8 kHz frequency band(P＜0.001).With increasing exposure duration,auditory damage in exposure group progressively worsened,and the most significant auditory threshold changes was found in the group exposed for over 15 years.The predictions made by the acoustic physical model closely matched the actual measurements,and the high model fitting degree(R2:0.85-0.90)in the long-term exposure group indicated a strong predictive capability for the cumulative effects of cochlear damage.Conclusion Long-term exposure to high-frequency noise in specific frequency bands results in significant cumulative damage to auditory function of the inner ear.Exposure duration and intensity are the primary independent risk factors.

Based on WeChat platform,blended teaching is designed and implemented in oral surgery practice.The undergraduate intern can get in touch with the internship early,become familiar with it early and make an internship program early.In the process of internship,they can achieve the purpose of getting more questions,more summary and more test through teaching,discussing and contesting.After the internship,they can consolidate,review,exchange and expand learning.The preliminary practice shows that the teaching stimulates the students' interest and motivation in the clinical study of oral surgery,enhances the interaction between teachers and students and the supervision of the teachers to the students,and improves the effect of the practice teaching.