Preprocessing of noisy speech for voice coders

Accurate linear prediction coefficient (LPC) estimation is one of the key requirements for low bit-rate voice coding. Under harsh acoustic conditions, LPC estimation can become unreliable. This results in poor quality of encoded speech and introduces annoying artifacts. The paper presents a two-branch speech enhancement preprocessing scheme for low bit-rate voice coders. The scheme consists of two parallel denoising blocks. One block enhances the degraded speech for LPC estimation. Another block increases the perceptual quality of the speech to be coded. The goal of the paper is to design the two-branch scheme. Test results show that the two-branch scheme can provide better perceptual quality compared to conventional one-branch speech enhancement techniques in noisy environments.