Investigation of Speech Coding Effects on Different Speech Sounds in Automatic Speech Recognition

Abstract

Automatic Speech Recognition (ASR) systems are increasing in usage for voice centric applications in mobile handheld and Voice over Internet Protocol (VoIP) based devices. The necessity is also increasing to find out the ASR performance under different network impediments when the recognition is performed in the remote servers, in real sense. Among the major impediments, speech coding is the one, which affects the ASR performance greatly, when using it with different sampling rates and bit rates in the practical systems. The speech codecs which use different algorithms for generating different bit rates will affect the speech sounds, i.e. vowels and consonants, differently, and cause the critical sounds in the words to be changed and in-turn affects the overall word recognition performance of the ASR systems. In this paper, the influence of the sampling rate and bit rate changes with different narrowband and wideband codecs on the speech sounds is analyzed. Investigation is carried out to see how the speech sounds are changing while using different codecs operating at different bit rates.