SUBJECTIVE ASSESSMENT OF THE INFLUENCE OF AUDITORY FREQUENCY CHARACTERISTICS ON THE MEASUREMENT OF AUDIOCONTENT LOUDNESS

Abstract

Research work on the improvement of algorithm of sound programs loudness is of great importance for modern broadcasting.  The article presents the results of an extended experimental study (based on subjective statistical evaluations) of the influence of auditory frequency characteristics on the perception of audio content loudness of various genres. The study is a continuation of previous work concerning the feasibility of modifying the second stage of pre-filtering in the loudness measurement algorithm specified in Recommendation ITU-R BS.1770-5.

In contrast to the previous stage of experiment, which involved 20 listeners, in the present study the number of participants are increased to 50, thereby improving the statistical reliability of the results and narrowing the confidence intervals, which are calculated in this article. The subjective statistical assessment of the perceptibility of loudness changes was carried out while adjusting the signal level in the frequency range above 1 kHz according to the 60-phon equal-loudness contour (Fletcher–Munson), the psophometric curve and the B-weighting curve. The assessment was fulfilled for different types of audiocontent – speech, both male and female, as well as music. The perceptibility of loudness changes exceeds or is close to 50% when using the 60-phon equal-loudness contour and the psophometric curve, thus indicating the significance of frequency correction in the range above 1 kHz.

The obtained results confirm the conclusion that it is advisable to take into account the frequency dependence of auditory sensitivity in the mid- and high-frequency parts of the sound frequency band when improving algorithms for the objective measurement of loudness of broadcast programs.