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Quality of Telephone-Based Spoken Dialogue Systems phần 5

E. một chương trình sơ đồ câu của ngôn ngữ được sử dụng, cung cấp một phân tích chính xác ngữ pháp, xác định thành phần của nó, ghi nhãn, xác định một phần của bài phát biểu của Hiệu lực của mạch hẹp ban nhạc tiếng ồn Nc. PESQ bình thường và dự đoán mô hình TOSQA cho tiếng nói tổng hợp so với tự nhiên. N cho dBmp = -100. | Speech Recognition Performance over the Phone 173 The simulation allows the following types of impairments to be generated Attenuation and frequency distortion of the main transmission path expressed in terms of loudness ratings namely the send loudness rating SLR and the receive loudness rating RLR . Both loudness ratings contain a fixed part reflecting the electro-acoustic sensitivities of the user interface SLRset and RLRset and a variable part which can be adjusted SLR and RLR f The characteristics of the handset used in the experiment were first measured with an artificial head head and torso simulator see ITU-T Rec. P.64 1999 for a description of the measurement method. They were then adjusted via SLR and RLR to a desired frequency shape which is defined by the ITU-T a so-called modified intermediate reference system IRS ITU-T Rec. P.48 1988 ITU-T Rec. P.830 1996 . In the case of high-quality microphone recordings or of synthesized speech cf. the next chapter the IRS characteristic can be directly implemented using the SLR filter. Continuous white circuit noise representing all the potentially distributed noise sources both on the channel Nc narrow-band because it is filtered with the BP filter and at the receive side Nfor wideband restricted by the electro-acoustic coupling at the receiver handset . Transmission channel bandwidth impact BP with 300-3400 Hz according to ITU-T Rec. G.712 2001 i.e. the standard narrow-band telephone bandwidth or a wideband characteristic 50-7000 Hz according to ITU-T Rec. G.722 1988 . For the reported experiment only the narrow-band filter was used. Impact of low bit-rate speech codecs Several codecs standardized by the ITU-T as well as a North American cellular codec were implemented. They include logarithmic PCM at 64 kbit s ITU-T Rec. G.711 1988 ADPcM at 32 kbit s ITU-T Rec. G.726 1990 a low-delay CELP coder at 16 kbit s ITU-T Rec. G.728 1992 a conjugate-structure algebraic CELP coder ITU-T Rec. G.729 1996 and a vector sum .