A speech enhancement technique for SAF army communication systems

Radio communication sets used in the Singapore Armed Forces (SAF) Army are undeniably one of the most essential modes of communication between the various elements during exercises and operations. While it has been a perennial problem in dealing with some of the short falls of these radio sets such as poor real-time reception and intermittent signals, little has been done to overcome them on a real-time basis to improve speech intelligibility and reception. In this paper, we make use of the concept of psychoacoustic signal processing based on the "missing fundamental phenomenon" to amplify weak signal receptions at low frequencies. Nonlinear device is used to induce virtual pitch that enhances the low frequency perception. However, some of the difficulties in using nonlinear devices include the need of precise adjustment over the magnitudes of the generated harmonics, harmonic order and its decay rate to achieve good perceived low frequency signal. Hence, we propose a technique on synthesis of polynomial-based nonlinear device complemented with spectrum shaping in an attempt to overcome these difficulties. Real-Time implementation and listening tests were conducted to verify the effectiveness of the proposed algorithm.