Monitoring of breath sound under daily environment by ceiling dome microphone

This paper proposes a new method for monitoring normal breath sounds in a daily environment where many kinds of noises exist. In a typical conventional breath monitor, a thermistor, an accelerometer, or a contact-type microphone must be attached directly to a person's body such as a part around the nose and the mouth, or a part over the chest wall and the trachea. This paper focuses on key issues stemming from a factor of the environment: extraction of breath sounds from sensor signals contaminated by environmental noise; and realization of a monitoring system suitable for our homes. Features of normal breath sounds are clarified by frequency analysis. Based on the features, a method for extracting normal breath sounds is discussed. This paper also describes a ceiling dome microphone which is a kind of a parabolic sound concentrator. It realizes a function of detecting normal breathing sounds with high sensitivity while keeping a room's appearance natural. The gain obtained by such a concentrator is analyzed theoretically from the acoustic point of view. Experimental results proved the feasibility of the proposed method.