To Design An Virtual Audio Analyzer Based On Virtual Instrument Structure

Audio analysis is widely used to measure time domain, frequency domain and distortion characteristics of various audio system. An all-around audio test and analysis needs all kinds of expensive special instruments, which should be well organized. Obviously, it is not a piece of cake for common user.Based on studying the fundamental theory of audio analysis, this paper puts emphasis on how to import virtual instrument technology into designing audio analyzer, and creates fire-new virtual audio analyzer. The main works and conclusions in this paper are as follows:(1) The existing audio analyzers' functions and their merits and defects are researched, and the goals of virtual audio analyzer are brought forward combined with thoughts of virtual instruments.(2) The contents, purposes and methods of audio analysis are studied. In Amplitude Analysis in time domain, the step impulse response acts as an important parameter to evaluate the performance of audio device. It reflects the response sensitivity of audio system to sudden changed signals. Audio devices' performances in playback are evaluated by their frequency response in the whole audio frequency range. There are several widely used methods to acquire the frequency response graph, including single tone method, multiple tone method, noise impulse method and Maximum Length Sequence signal impulse method. The last method, MLS signal impulse, has so obvious predominance in the aspect of decreasing noise as to obtain increasingly wide use. Harmonic distortion is one of the most common non-linear distortions, and it affects the playback performance of audio devices directly. Harmonic distortion graph reflects the distortion distribution in the whole audio frequency range.(3) Using structurization thought in software engineering, the design of virtual audio analyzer is divided into five parts, which are data acquisition, analysis, displaying, auxiliary and control. The five parts are realized in the form of software modules. They provide different functions inside and uniform interfaces outside. They cooperate each other and make up an integrated audio analysis system.(4) The loudspeakers of sound box are tested using virtual audio analyzer, and some audio characteristics are obtained.(5) Finally, the further assumptions are brought forward with three aspects, which are integration of hardware, object orientation of software and network based application.QLVAF-1 type of virtual audio analyzer, which is developed by the authorsindependently, can be applied to measurement of varied audio devices. The analyzer provides versatile measure and analysis functions to meet the requirement of audio devices, including measure of audio signal's volt and frequency, Amplitude Analysis in time domain, Amplitude Analysis in frequency domain, analysis of distortion, etc. Using the analyzer, users can make up useful audio analysis system and carry through various audio tests.