| Summary: | 碩士 === 國立交通大學 === 電子研究所 === 100 === In modern binaural hearing aids, the realization of many advanced functions depends on reliable exchange of information for both sides. Commercially available hearing aids often use RF technologies to meet the communication needs, despite the relatively high power consumption associated with them. However, most advanced hearing aids are battery-operated, and with their small sizes the capacity of the accompanied batteries is quite limited. Therefore, in view of the practicality of binaural hearing aids, it is necessary to develop a low-power communication system. On the other hand, experiments are conducted to verify the channel characteristics of the waveguide type are good enough to support the proposed binaural communication system. And, due to the facts that skin contact naturally happens in binaural hearing aids and baseband modulation techniques with low power consumption can be used in transmission over skin, the skin communication system is found to be perfectly suited for the needs of binaural hearing aids.
This thesis presents a communication system with skin channel technology. To meet the needs of binaural hearing aid systems, we follow the following design guidelines. First, the group delay time is strictly limited. According to [1], if the audio and visual cues have delays more than 10 milliseconds, human beings are prone to sense the confusion in verbal cognition. So, this is the top-priority consideration. Second, the communication should have synchronization capability. It is important for applications where the cues of Interaural Time Difference (ITD) or Interaural Level Difference (ILD) are used to extract desired speech signal from the mixture of speech signal and noises from different directions. And last, the power consumption should be as low as possible.
This thesis is organized as follows. Chapter 1 introduces the structure of hearing aids and the feasibility study of a body channel communication system for binaural hearing aids. Chapter 2 presents a case study of IEEE 802.15.4 WPAN, and I try to learn from the analysis what kinds of protocols and specifications are needed for a body channel communication system. Chapter 3 discusses the trade-offs of designing a communication system for binaural hearing aids, particularly from the aspect functions and practicality demanded by hearing aids. Chapter 4 presents the design/implementation details of the binaural communication system. Chapter 5 summarizes this thesis and proposes future directions of further development.
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