| The crew is a special group, they work for a long time in a noisy environment of the ship, the environment is relatively closed and the noise intensity is large, hearing loss will gradually involving speech frequency, there will be noise induced hearing loss. With the help of the crew suffering from noise induced hearing loss, the hearing aid can help can help patients solve the inconvenience in their lives. In this paper, based on the current research status of digital hearing aids, and analysis of the development needs of wireless digital hearing aids, digital hearing aids system is proposed, it consists of wireless hearing aids and relay device. The system uses SA3291 chip combined with ultra- low-power Near-field Magnetic Induction Communication wireless technology to research and development of wireless digital hearing aids, a dimensional inductive antenna is designed for omnidirectional NFMI communication, a new circuit of wireless digital hearing aids and acoustic structure are designed to meet the requirement of acoustic space and resistance to electromagnetic interference, binaural hearing aids can be realized by audio peering through NFMI and parameters synchronization, the communication distance between the ears can be up to 20 cm, power consumption is about 2.5. In addition to resolve the problem of audio and data reliable transmission between relay device and hearing aids, we have put forward Message Channel Protocol, relay device connect with other audio devices through the Bluetooth protocol. We send audio and parameters to the hearing aids by NFMI, the communication distance up to 80 cm.This subject completed the development of wireless digital hearing aids, experimental results showed that the system has realized the design target of the main requirements. Experimental results also meet acoustic standards : equivalent input noise ≤ 32 d B, total harmonic distortion ≤10%, operating current ≤3m A, it allowed hearing- impaired users can use the high performance of hearing aids, it also has important significance to promote the development of technology of wireless digital hearing aids and increase the embedded audio industry. |
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