| 摘要 |
In an encoder device which is for use in combination with a decoder device in a communication system and which encodes a sequence of digital speech signals into a sequence of output signals by the use of a spectrum parameter and a pitch parameter, a subsidiary parameter of the digital speech signals is detected and by a monitoring circuit to classify the digital speech signals into a voiced sound and a voiceless sound or into vocality, nasal, fricative, and explosive at every frame. On detection of the voiced sound or the vocality, a predetermined number of excitation pulses are calculated only during a representative subframe after dividing each frame into a plurality of subframes by the use of the pitch parameter and are produced as primary sound source signals together with a subsidiary information signal which is produced during the remaining subframes and which may be representative of a correction factor of an amplitude and a phase in each of the subframes. On detection of the voiceless sound or the nasal, the fricative, and the explosive, noise signals and/or a plurality of excitation pulses are calculated for each frame and produced as secondary sound source signals. Alternatively, the subsidiary parameter may represent periodicity of an impulse response of a synthesizing filter formed by the spectrum parameter. |
