Research And Implementation Of Audio Loudness Test And Control System

Abstract:At present, digital television has already popularized in our country. With its popularity comes the issue of loudness. Loudness is a subjective feeling of audience that defines sound intensity. The audience’s requirement for audio quality is increasing while facing digital TV. In order to let audience enjoy the comfort of audio effect when enjoying high quality of video, the loudness of audio must be adjusted before audio is transmitted to audience. Thus, this paper focuses on research of audio loudness test and control system.According to system requirement analysis, an algorithm of loudness control plan which combining loudness test and audio process is proposed from the background of our country. Systems of loudness test and loudness control is studied and analyzed in this paper respectively. And these systems are implemented on DSP. Compared to other audio compressors that use compression ratio to control level and loudness, loudness test algorithm in ITU-R BS.1770-2standard that is applies in broadcast system is utilized as prerequisites of loudness control for the first time in this paper. In addition, this paper uses special method that conducts separate operations to audio data and noise when implements loudness control system. In this way, misuse of low decibel noise that leads to damage to audio quality can be avoided. In this paper, simulation is conducted on MATLAB7.0in research of loudness test algorithm. The variation of loudness is tested through altering level, time and frequency. According to the results of simulation and analysis of loudness test algorithm, loudness control plan based on ITU-R BS.1770-2is proposed. Then, The software design plan of loudness control system based on C programming language is presented in this paper, and the system is implemented in VC6.0platform. At last, a real-time audio loudness control system based on DSP is implemented using ADSP-21489of ADI as hardware platform in this paper. After completion of the system, this paper uses systematic way of validation to run test on functional integrity, stability and sensitivity. The result also meets the expected requirement.Audio loudness control system solves the problem of loudness inconsistency by adopting loudness test algorithm in ITU-R BS.1770-2. Using DSP makes the system possess features such as high-speed processing, and easy to upgrade and transplant. With the increasing demands for quality of multi-channel audio and audience’s growing awareness of loudness, more automatic control of loudness is becoming a new research and development direction.