So-called full-face masks are essential for fire fighters to ensure respiratory protection in smoke diving incidents. While such masks are absolutely necessary for protection purposes on one hand, they impair the voice communication of fire fighters drastically on the other hand. For this reason communication systems should be used to amplify the speech and, therefore, to improve the communication quality. This paper gives an overview of communication enhancement techniques for masks based on digital signal processing. The presented communication system picks up the speech signal by a microphone in the mask, enhance it, and play back the amplified signal by loudspeakers located on the outside of such masks. Since breathing noise is also picked up by the microphone, it’s advantageous to recognize and suppress it – especially since breathing noise is very loud (usually much louder than the recorded voice). A voice activity detection distinguishes between side talkers, pause, breathing out, breathing in, and speech. It ensures that only speech components are played back. Due to the fact that the microphone is located close to the loudspeakers, the output signals are coupling back into the microphone and feedback may occur even at moderate gains. This can be reduced by feedback reduction (consisting of cancellation and suppression approaches). To enhance the functionality of the canceler a decorrelation stage can be applied to the enhanced signal before loudspeaker playback. As a consequence of all processing stages, the communication can be improved significantly, as the results of measurements of real-time mask systems show.

中文翻译：

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消防员使用的通信系统的信号增强

所谓的全面罩对于消防员来说是必不可少的，以确保在烟雾潜水事件中保护呼吸系统。虽然这种口罩一方面是出于保护目的绝对必要的，但另一方面它们会严重损害消防员的语音交流。出于这个原因，应该使用通信系统来放大语音，从而提高通信质量。本文概述了基于数字信号处理的掩模通信增强技术。所提出的通信系统通过面罩中的麦克风拾取语音信号，对其进行增强，并通过位于这种面罩外部的扬声器播放放大的信号。由于呼吸噪音也会被麦克风拾取，识别和抑制它是有利的 - 特别是因为呼吸噪音非常大（通常比录制的声音大得多）。语音活动检测可区分旁白、暂停、呼气、吸气和讲话。它确保只播放语音组件。由于麦克风靠近扬声器的位置，输出信号会耦合回麦克风，即使在中等增益下也可能发生反馈。 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 这可以通过反馈减少（由抵消和抑制方法组成）来减少。为了增强消除器的功能，可以在扬声器回放之前对增强信号应用去相关级。由于所有处理阶段，通信可以显着改善，