Evaluation of Live Loudness Meters

Discrepancies in loudness (i.e. sensation of audio intensity) has been of great concern within the broadcast community. For television broadcast, disparities in audio levels have been rated the number one cause to annoyance by the audience. Another problem area within the broadcast and music industry is the loudness war. The phenomenon is about the strive to produce audio content to be at least as loud or louder to any other audio content that it can easily be compared with. This mindset, when deciding for audio level treatment, inevitably leads to an increase in loudness over time, and also, as a technical consequence, a decrease of utilized dynamics. The effects of the loudness war is present in both terrestrial radio transmissions as well as in music production and in music distribution platforms. The two problems, discrepancies in loudness and the loudness war, both emanate from the same source; regulations of audio levels and the design of measurement gear have not been amended to cope with modern production techniques. At the time when the work on this thesis started, the ruling technical recommendations for audio level alignment were based on peak measurement. This measured entity has poor correspondence to loudness. To counter the above described problems, the European Broadcasting Union (EBU) and the International Telecommunication Union (ITU) has developed new recommendations for audio alignment, EBU R 128 and ITU-R BS.1770. The new definitions for loudness measurement constitutes simplified models on the human perception of audio intensity. When using the new recommendations in production, the problems have been shown to diminish. For an engineer in a live broadcast scenario, measurement equipment also need to be updated in real-time to illustrate a time-variant loudness of the signal. EBU and ITU also has regulated how this type of measurement gear should behave. EBU Tech 3341 and ITU-R BS.1771 define properties for live loudness meters. These recommendations has since the time of publication been implemented in measurement equipment from manufacturers and become available in production facilities. This thesis investigates the conceptions that have led up to the present recommendations for live loudness meters. It maps out the (at the time) present ways to evaluate the same. Emanating from this knowledge, a new methodology to evaluate loudness meters is proposed that combines qualities from former methods to achieve an alternative balance between ecological validity and control in the experiment design. The methodology includes a procedure to capture data from engineers’ actions and the resulting audio levels from simulated broadcast scenarios. The methodology also incorporates a way to process this type of data into different parameters to be more accessible for interpretation. It presents an approach to model the data, by the use of linear mixed models, to describe different effects in the parameters as the result of the meters’ characteristics. In addition, a review on publications that examine the engineers’ own requests for beneficial qualities in a loudness meter has been condensed and revised into a set of meter criteria that specifically is designed to be applied on the outcome of the mixed models. The outcome of the complete evaluation yields statements on meter quality that are different and complementary to formerly proposed methods for meter evaluation. The methodology has been applied in two different studies, which also are accounted for in the thesis. The conclusions from these studies has led to an increased understanding of how to design live loudness meters to be satisfactory tools to the engineer. Examples of findings are: the effect of the speed of the meter, as being controlled by one or several time constants, on the readability of the meter and the dispersion in output levels – some tested candidates, with higher speed than the present recommended ones, has been shown to be adequate as tools; the three-second integration time has been shown to generate a smaller dispersion in output levels than the 400 ms integration time; the effect of the gate in BS.1771 on the resulting output levels– the gate generally leading to an increase in output levels. The acquired knowledge may be used to improve the present recommendations for audio level alignment, from EBU and ITU