Audible (normal) speech and inaudible murmur recognition using NAM microphone

In this paper, we present audible (normal) speech and inaudible murmur hidden Markov models based automatic speech recognition using NAM microphone. The NAM (Non-Audible Murmur) microphone is a special device, which can be used for capturing inaudible murmur speech. The device is based on the stethoscope, which is used in medical science. By attaching the NAM microphone behind the talker´s ear, we can receive very quietly uttered speech and perform automatic speech recognition in a conventional way. Privacy, robustness to environmental, and a useful tool for sound-impaired people noise belong to the advantages of the NAM microphone. Using adaptation techniques, we created hidden Markov models for inaudible speech and we performed automatic speech recognition. The achieved results are very promising, and prove the effectiveness of NAM microphone In this paper, we also introduce our work for recognizing normal speech using NAM microphone. The idea is to take advantage of noise robustness of NAM microphone. In our experiments, we achieved a 93.8% word accuracy in clean environment, and a 93.1% word accuracy in noisy environment. In this paper, we also introduce two techniques to intergrate inaudible murmur and audible speech recognition using NAM microphone. In both cases, we achieved a 92.1% word accuracy on average, which is a very promising result.