Speech enhancement in noise and within face mask (microphone array approach)

In certain communication environments, digital speech transmission systems must work in severe acoustic environments where the noise levels exceeds 110 dB. In other environments, speakers must use an oxygen face mask. In both situations, the intelligibility of encoded speech falls below an acceptable level. We have developed a technique for improving speech quality in these situations. Previous speech improvement methods have focused on processing the corrupted signal after it has been induced by the microphone. These methods have not performed adequately. In our technique, speech anomalies are attenuated by a microphone array before speech and noise become mixed into a signal. Our microphone array prototype has shown excellent performance. In an example of speech taken aboard an E2C aircraft, this noise-canceling microphone array improved the speech-to-noise ratio by as much as 18 dB. When the same technique is used in a face mask, muffled speech was almost completely restored to high quality speech.