Research And Development Of Objective Evaluation System Of Sound Quality

The research of sound quality began from nineteen eighty's. In recent ten years, sound quality had been a new field which involves aviation, railroad, automobile and so on. Lots of researchers are interest in the field and get much success. The appraisal of the interior sound quality is concerned with not only acoustics, mechanics and signal processing, but also psychology, physiology. So, the sound quality appraisal is a extremely complex question. The objective evaluation of the sound quality is very important in research of sound signal processing. Objective sound quality evaluation offered a convenient, objective and reproducible means while evaluating the performance of sound signal. However, up to the present, the research on the objective evaluation system of sound quality is insufficiency. Objective evaluation has not established a self-contained system theoretically and actually. In this paper,The objective evaluation system of the sound quality based on the subjective appraisal. In order to appraise the validity of the objective evaluation of sound quality, the subjective appraisal of the vehicle interior sound quality is applied to ascertain whether the method can forecast subjective appraisal correctly.At the beginning of the paper I sum up the definition and basic theoretics about sound quality. I introduce the international condition and other characters. At last of this part I choose some suited parameters to evaluate the sound quality of vehicle.Next, I make the computing program by Matlab. A great deal of research express that, in some cases, the noise level measured in dB(A) can not match the feeling of people. the person's impression to the voice is decided by these parameter: loudness, sharpness, roughness and fluctuation etc.. Loudness mainly considers the distribution of the characteristic frequency band and tne auditory masking. Sharpness reflect the relation between the distribution of the characteristic frequency band and the loudness level. Roughness and fluctuation reflect the fluctuant sound. The program can compute loudness, sharpness, roughness and fluctuation. The definition has been checked by the mature software.The third, Develop a analysis system of the objective evaluation of sound quality. The software form can use the strong calculation ability and the sketch function of the computer, reflect the people's feeling to the sound with the figure. On the foundation of the fourier transformation theories, consider the problem of the discrete fourier transformation, give the realization and the compute procedure of 1/3 frequency filter. Develop a analysis system of the objective evaluation of sound quality .In the last section,given the relationship between the objective and the subjective evaluation of the sound quality. The subjective evaluation of the sound quality is according to the feeling of an or a group people to the sound and giving a quality level from the certain previous measure . I make the subjective test with four different cars. By statistical way I get the relationship between the subjective test and objective test. The result present that the parameters of sound quality can give the reflection from psychology.