Establishment of Speech Communication under Very Heavy Environmental Noise

一般来说，骨传导麦克风可以消除周围的噪音，通常用于船舶的机舱或机场的跑道等极端嘈杂的环境。它能探测颌骨等骨骼的振动，并将振动转化为声音。不幸的是，这个麦克风转换的声音的质量不利于顺畅的交流。因此，本研究的目的是开发一种骨传导语音到空气传导语音的语音转换算法，以便在极度嘈杂的环境中提供一种流畅的语音通信方式。本研究的结果如下：提出了一种新的双单元自组织映射（TW-SOM），该映射能够高精度地描述非线性输入输出关系，并将其应用于语音转换中。具体来说，TW-SOM通过双单元学习骨骼和空气传导声音之间的非线性关系。经其学习后，应用于TW-SOM的骨传导语音转换为相应的空气传导语音。通过与传统SOM和其他神经网络方法的比较，验证了所提语音转换方法对实际船舶装卸词的有效性。结果表明，该方法比其他传统方法更适合于硬件实现。对其他领域适用性的检验所提出的方法中使用的码本的关键思想成功地应用于图像扩展，以获得清晰的图像。TW-SOM是精确描述包括语音转换在内的各种非线性映射的通用方法。然后，我们将在未来的研究中考察其在其他领域的适用性。

In general, a bone conduction microphone, which eliminates surrounding noise, is often used in extremely noisy environments such as engine rooms in ships or runways at airports. It detects the vibration of bones such as jaws, and it converts the vibration to voice. Unfortunately, the quality of this voice converted by this microphone is bad for a smooth communication. Therefore, the aim of this research is to develop an algorithm of voice conversion from a bone conduction voice to an air conduction voice, in order to supply a smooth communication method by voice in the extremely noisy environments. The results of this research are the following.1. Voice Conversion by the Proposed TW-SOMA new type of self-organizing map with twin units (TW-SOM), which can describe a nonlinear input-output relation with high accuracy, was proposed, and was applied to voice conversion. Concretely, TW-SOM learns a nonlinear relation between the bone and the air conduction voices by the twin units. After its learning, the bone conduction voice applied to TW-SOM is converted to the corresponding air conduction voice.2. Verification of the Effectiveness of the Proposed Method and Application to Actual Ship-Handling WordsThe effectiveness of the proposed voice conversion method was verified for actual ship-handling words by comparing with the conventional SOM and other competing neural network methods. It was also confirmed that the proposed method is more suitable for a hardware implementation than the other conventional methods.3. Examination of Applicability to Other FieldsThe key idea of the codebook used in the proposed method was successfully applied to an image expansion to get a clear image. TW-SOM is a general method to describe precisely the various nonlinear mappings including voice conversion. We would like then to examine its applicability to other fields as future studies.