Speech and audio loudness depending on telephone audio bandwidth and codec — A subjective testing approach

In this paper, we propose a new approach for the subjective assessment of the loudness of complex audio signals such as speech or music. This two-stage approach makes it possible to study the influence on loudness of the frequency bandwidth and of different kinds of codecs. In the first stage, the individual loudness function of each subject is estimated using a specific 100-point response scale. In the second stage, the subject evaluates the loudness of each processed sample, by filtering or coding/decoding, using the same scale. The loudness obtained in terms of points is then converted in loudness levels in terms of phons using the estimated individual loudness function. Results show that loudness increases with the bandwidth extension up to super-wideband. Similar behavior is observed when codecs are applied.