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利用数字式2400 bit/s通道声码器作手段,研究数字语言通信系统的语言质量评价问题。在几种不同的传递条件下,进行了语言清晰度试验。这些传递条件包括;1.语言信号经过低通3400Hz滤波,2.语言信号经过低通3400Hz滤波以后,再进行脉码调制,3.语言信号经过2400 bit/s声码器,4.语言信号经过声码器,但采用不同的激励源(a.单纯用白噪声,b.基频随语言输入变化的三角波,c.基频固定的三角波)。对数字语言信号处理系统和模拟语言信号处理系统的语言质量进行了对比研究。结果表明:1.数字语言信号处理系统的语言质量降低主要表现在辅音清晰度较低,2.要想对各个语音的质量作出评价和诊断,需要使用较多的试验表,3.在语言信号结构没被破坏的条件下,在模拟语言信号处理系统上建立的不同语言单位清晰度试验得分间的统计关系,对数字语言信号处理系统也是适用的,4.数字语言信号处理系统和模拟语言信号处理系统工作性能的对比研究,有助于检验数字处理系统语言质量降低的原因。
Using the digital 2400 bit / s channel vocoder as a means to study the language quality evaluation of digital language communication system. Under several different delivery conditions, language proficiency tests were conducted. These transmission conditions include: 1. The speech signal is filtered through the low-pass 3400Hz, 2. The speech signal is filtered through the low-pass 3400Hz, and then the pulse code modulation is performed. 3. The speech signal passes through the 2400 bit / s vocoder, 4. The speech signal passes Vocoder, but with different excitation sources (a. Purely white noise, b. Fundamental frequency with the language input changes triangular wave, c. Fundamental frequency fixed triangle wave). The language quality of digital speech signal processing system and analog speech signal processing system are compared. The results show that: 1. The reduction of speech quality of digital speech signal processing system is mainly manifested in the low consonants, 2. To evaluate and diagnose the quality of each speech, more test tables are needed.3. The statistical relationship between the sharpness test scores of different language units established on the analogue speech signal processing system is also applicable to the digital speech signal processing system under the condition that the structure is not damaged. 4. Digital speech signal processing system and analog speech signal A comparative study of the working performance of the system helps to examine the reasons for the degradation of the language quality of the digital processing system.