The Design Of Audio Detection System Based On Virtual Instrument Structure

Voice interruption, noises, howling and other emergencies frequently occur when holding a multimedia conference and sometimes it is very hard for professional maintenance personnel to find out the reasons of failures, which is a huge hindrance to the meeting. To this situation, it is supposed to design a audio detection system based on virtual instrument structure. The system is designed based on digital signal processing skills, signal detection technology, virtual instrument technology, computer technology and in reference to intelligent audio measurement instrument technology both at home and abroad. The system is aimed at testing equipment performance index before the meeting starts, monitoring equipment during the meeting, and recording, storing, reporting trouble spots to ensure that equipment maintenance personnel can find out and solve them in time.First of all, There are disadvantages in the current multimedia conference system according to the analysis of a large number of materials about virtual instrument technology and intelligent detection equipment technology at home and abroad. So, A design thought based on virtual instrument structure of conference audio detection system is proposed--according to virtual instrument structure model, using hardware using hardware to access the measured signal and software to detect, monitor and display dominating audio signal. Without any changes of hardware, testing content ought to be modified according to users' requirement, while storage side separated from display in data collecting and analysis of software, connecting by a display client with multiple signal collecting and analysis side to achieve that one can simultaneously carry on real-time detection for multiple conference room equipment.This design greatly increases flexibility and efficiency of the system and saves the cost of hardware and human resources.Secondly, the basic theory of system is studied, which include digital signal analysis theory and digital audio equipment related theories. The aspect of digital signal analysis: short time Fourier transform is mainly analyzed and researched and its achievement difficulties in algorithm is pointed out. To solve the problem, the short time fast Fourier transform(FFT) is considered. However FFT may cause spectrumleakage and fence effect which can be improved by choosing the right window function when the signals are truncated in time domain. Digital audio equipment related theory aspect: the advantages of digital audio technology are stated; the commonly used features and their calculation methods of the audio equipment performance indicators are analyzed and improved, and two new detection parameters--break detection and squeaking detection are presented, and their detection algorithms are studied in detail.Thirdly, with overall design and analysis of functional requirements, the conference audio detection system is consisted by four parts according to the structural model of virtual instrument: client module, signal acquisition and analysis module, sound module and signal access module. The functions of each parts and the features of the whole system are specifically stated. Then the system's hardware components are designed, and the development tool of its software part is introduced.Then, according to the general requirements of the system design, the core of the system is proposed—— the design thought and programming realization of signal acquisition and analysis module. According to modularized design methodsit is divided into four parts: signal acquisition module, algorithm analysis module, the communication control module and data storage module. The signal acquisition module is implemented by using the sound card to capture audio signal and using Win API functions to program. The algorithm analysis module is programmed by writing a class named “Algorithm” to contain SFFT algorithm, audio equipment performance index detection algorithm, audio online monitoring parameters calculate algorithm and parameters passing. The communication control module is used to realize the communication between signal acquisition and analysis module and sound source box,signal acquisition and analysis module and the client module. The data storage module is used to store the audio test results and monitoring results.Finally, the design ideas and programming approaches of human-computer interaction part- client module of the system is proposed. It is divided to seven modules: initial configuration part, device detection part, online monitoring part, data logging inquiry part, troubleshooting part, instrument configuration part, network testing part. Then the specific implementation of each module are described in detail and.After completing the theoretical research and system design, the interfaces of system software are showed by pictures and it prove that the system can operate normally, and realize expected functions which are device testing, on-line monitoringand fault reporting. Also according to displayed faults, the positions of error in conference multimedia system can be found easily. The results demonstrate that the system can help the equipment maintenance personnel to test and monitor the meeting equipment to make sure them work properly during the meeting and to confirm that the meetings are conducted effectively.