PERFORMANCE OF SOUND MASKING SYSTEM FOR MOBILE PHONE USING COMB-SHAPE NOISE

The mobile phone conveniently allows its users to have a voice communication regardless of place, including public area. However, telephone conversations sometimes contain a private information. To provide speech confidentiality, we propose sound masking system for mobile communication. However, to realize sound masking system for mobile phone, we have to address two problems: time-variation of mobile communication environment and limited computational power of mobile phone. The channel between noise generator and microphone changes drastically due to the movement of the user. Moreover, the complexity of the noise filter should be simplified considering the computational capacity of the mobile phone. In this paper, we propose a simple system that uses comb-shape noise to cover up a human speech, and comb-type filter for filtering. Although comb-shape noise is effective for masking, the calculation cost at the filtering process can be minimized because it does not require any coefficient update. We implemented the sound masking system on mobile phone mock-up, and evaluated its performance in experiment. As a result, it was found that the noise reduction performance of the proposed system is better than that of the adaptive filtering. Consequently, the proposed system is suitable for sound masking system for mobile phone.