Progress in standardization of 3D-audio loudness in ITU-R BS.1770
The calculation of loudness for up to five channels is defined in ITU-R BS.1770-3. New 3D audio transmission formats and reproduction systems are standardized and in use (cinema reproduction systems). The 22.2 format will be used at the Olympic Games 2016 for broadcast in Japan. These international activities ask for an expansion of the loudness calculation of BS.1770 towards 3D audio. Therefore, new loudness adjustment tests with 3D audio material were conducted. A pre-test revealed that a mouse wheel adjustment method takes half the time as a forced choice test and has the same accuracy. Test requirements, design and procedure of the main loudness adjustment test are described and results are presented. The metrics of different fitting attempts under the assumption of backward compatibility are presented. The upcoming Revision of ITU-R BS.1770 will use a factor G = 1.41 for the azimuth range [60°..120°] for elevation 0°, and G = 1 for all other directions. Open issues like loudness calculation for moving objects and Higher Order Ambisonic signals still have to be evaluated and defined.