| Line check in the secondary circuit is an important part of electrical system.Once something wrong goes with line check there will be serious electrical accidents.The intelligent line-checked device in this thesis is an intelligent apparatus speciallyfor line check in the secondary circuit of the electrical system. It is widely employedin the electrical system for its efficient line check and diversified functions.However,the original line-check steps of intelligent line-checked device are veryburdensome in daily detective line-check, so a voice transmission system needsbuilding according to the requirement of the staff to further improve the efficiencyof line-check.The thesis presents an in-depth study on the design and implementationof the intelligent line-checked device speech transmission system, with theapplication of MELP vocoder algorithm in the intelligent line-checked device.First, given the practical operation of the intelligent line-checked device, it isnecessary and feasible to design a speech transmission system. Reasons for adoptingMELP vocoder can be found in the thesis. The performance requirements of thespeech transmission system are analyzed according to work environment and contentof the intelligent line-checked device. On this basis the thesis presents the summaryof the overall structure of the transmission system.Secondly, based on the speech coding theoretical basis of MELP, a deep study iscarried on the calculation, quantization and decoding of parameters of MELP coding.The MATLAB simulation and analysis for the calculation and quantitative results ofthese parameters are presented and compared with the result of algorithm. Theadoption of three level center slicing method optimizes the pitch extractionalgorithm, significantly reducing the computation load without affecting speechquality and improve the stability of the voice transmission system.Next, the hardware system of the line-checked device speech transmissionsystem is constructed, with C8051F020as the communication control core,TMS320VC5509A as the data-processing core and TLV320AIC23B as the speechprocessing front end. The source code of MELP is optimized. Through the processanalysis of the main software module and some key code analysis, especially the interconnected electronic circuits of communication module and channel interface ofthe master and the slave device, it finds that the speech transmission system withtwo-way voice communication can be realized with single wire core.Finally, the actual circuit board is made according to the above theory. A test forthe intelligent line-checked device speech transmission system is then conducted bysimulating the speech communication in the process of line check. The comparisonresult of the time domain waveform when speech signal is input and output byoscilloscope and the listening result show that the system has rapid speechtransmission and the synthetic speech at the receiving end is clear and distinct. Thespeech of the system has been tested10times by PESQ, an international speechassessment method. The score result shows that the synthetic speech of the systemreaches the communication quality standards and can guarantee that the speechcommunication flows smoothly. In a word, judging from the time domain waveformof the synthetic speech tested by oscilloscope and the PESQ score result, the speechcan be rapidly and precisely transmitted through the system. |
