Subjective and objective evaluation of sound quality of radio programs transmitted via Digital Audio Broadcast [DAB+] System

Abstract

The work presents results of research on the sound quality of different radio programs transmitted via Digital Audio Broadcasting (DAB+). This assessment has been provided with a use of psychoacoustic model as well as standard listening tests, using an ACR (Absolute Category Rating) method of scaling, and CCR (Comparison Category Rating) method. Results have shown that sound quality gets worse when bit-stream is of the lowest values (48 kbit/s or 24 kbit/s). Application of the Spectral Band Replication processor significantly improves the perceived quality, which is satisfying for bit streams higher than 64 kbit/s, particularly for jazz and popular music. The assessment with ACR method (recommended for broadcast by International Telecommunication Union) showed better notes than CCR one. It means that recommended method is less critical. Also results obtained with psychoacoustic model are more similar to obtained with CCR method. The attributes of spatial impression change in different ways. The greatest distortion has been observed for the perspective and spaciousness of sound image, while the sound color as well as localization stability and accuracy of phantom sources remained almost the same.