The purpose of this study was to evaluate how the BS.1770 Loudness Standard is affected by the amount of difference signal present in the signal being measured, and if this affection is different between the two playback systems Headphones and Loudspeakers. The study was restricted to rock music productions in a stereo format. The results obtained from the study might provide useful information to mixing and mastering engineers, as it evaluates the correlation between spatial information and subjective loudness. The study consisted of an active listening test, containing six stimuli with different Sum and Difference Ratio (SDR). The test was done in both headphones and loudspeakers, and the difference in volume as set by the subjects were noted. The results from the headphone version and the loudspeaker version were then compared in a paired t-test to see if there was a significant difference between the two formats. The results pointed to the factors of Playback System and SDR to have non- significant effect on the results. After analyzing the possible error sources, it became apparent that other factors had a far greater effect on the results. The results imply that the BS.1770 Loudness Standard can accurately measure the loudness of a given stereo rock music material, despite the fact that it does not consider the differences between the channels when conducting the measurement. Whether or not the effect being studied is significant in other conditions is not verified, due to the restrictions of the study. Further studies would be needed in order to verify the findings of this study, preferably with more attention to detail since there were apparent flaws in the method used.

This thesis deals with basic methods of root mean square and peak value measurement of a digital acoustic signal, algotithms to measure audio programme loudness and true-peak audio level according to recommendation ITU-R BS.1770-1 and digital systems for control of signal dynamic range. It shows achieved results of root mean square and peak value measurement and results of implementation of dynamic processor with general piecewise linear non-decreasing static curve and algorithms according to recommendation ITU-R BS.1770-1.