A background noise suppression system developed by Motorola is included as a feature in IS-127, the TIAlEIA standard for the Enhanced Variable Rate Codec (EVRC) to be used in CDMA based telephone systems. In this paper, we describe the algorithm used in this system and its implementation. We then present subjective listening test results showing the advantages of using such a system as a prefilter to a speech coder.

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In this paper we present work that has been carried out in developing the ETSI Extended DSR standards ES 202 211 and ES 202 212 [1][2]. These standards extend the previous ETSI DSR standards: basic front-end ES 201 108 and advanced (noise robust) front-end ES 202 050 respectively. The extensions enable enhanced tonal language recognition as well as server-side speech reconstruction capability. This paper discusses the server-side speech reconstruction whereas a companion paper discusses the front-end extension and tonal language recognition. Experimental results show that the reconstructed speech produced by the standards is highly intelligible under clean and noisy background conditions with the DRT (Diagnostic Rhyme Test) and TT (Transcription Test) scores meeting or exceeding the objective values corresponding to the US DoD (Department of Defence) Federal standard MELP (Mixed-Excitation Linear Predictive) coder operating at 2400 bps.

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