Study On Air-bone Conduction Difference Transfer Function Based On Otoacoustic Emission

Bone conduction(BC)transmits sound waves to the cochlea through the skull.Compared with air conduction(AC),BC opens the ear canal to ensure that people do not lose the external acoustic information while listening.In recent years,BC hearing aids and BC headphones have been more and more widely used.Because audio signals are usually designed for AC playback,measuring the Bone to Air Differential Transfer Function(BADTF)is essential to improve the playback performance of BC devices.Measuring BADTF involves measuring the Air Conduction Transfer Function(ACTF)and Bone Conduction Transfer Function(BCTF),which are defined as the transmission characteristics between the excitation signal of the AC device or BC vibrator and the cochlea respectively.Because Stimulus Frequency Otoacoustic Emissions(SFOAE)serve as an objective reflection of the cochlea’s response to external stimuli,the BADTF based on SFOAE is defined as the ratio of SFOAE obtained by feeding the same input stimulus signal with AC and BC method.This paper uses SFOAE to measure BADTF and compares it with the subjective BADTF method based on hearing threshold.The similarity of experimental results verifies the reliability of the method based on SFOAE.The research in this paper has certain research significance and value in exploring the transmission characteristics of human BC,improving the performance of BC sound reproduction,and promoting the application of BC devices.The research contents and main innovations of this paper are summarized as follows:(1)An objective measurement method for BADTF has been proposed.SFOAE was used to measure BADTF,while repeated measurements and comparative experiments were conducted.The experimental results indicated that the BADTF measurement method based on SFOAE had good repeatability and could well reflect the physiological characteristics differences between the air conduction sound transmission system and bone sound transmission system of human.(2)A comparative study was conducted between the BADTF based on SFOAE measurement method proposed in this article and the BADTF based on hearing threshold measurement method.The experimental results showed that the BADTF measured using the SFOAE method and the BADTF measured using the auditory threshold method were similar in mid to low frequencies.Comparing the BADTF based on SFOAE with previous BADTF results based on the hearing threshold,the similarity of their results proves the reliability of the BADTF measured using the SFOAE method.(3)The measurement of the BC SFOAE based on swept tone was conducted in this paper,the influencing factors of the BC SFOAE results were discussed,and the BADTF measurements based on SFOAE using swept tone were explored.