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Evaluation of Live Loudness Meters ISBN 978-91-7790-297-3 (Pdf) DOCTORAL T H E SIS Department of Arts, Communication and Education Division of music, media and theater ISSN 1402-1544 ISBN 978-91-7790-296-6 (print) Evaluation of Live Loudness Meters ISBN 978-91-7790-297-3 (pdf) Luleå University of Technology 2019 Jon Allan Evaluation of Live Loudness Meters of Live Allan Evaluation Jon Jon Allan Audio Technology Evaluation of Live Loudness Meters Jon Allan Luleå University of Technology Department of Arts, Communication and Education Division of music, media and theater Printed by Luleå University of Technology, Graphic Production 2019 ISSN 1402-1544 ISBN 978-91-7790-296-6 (print) ISBN 978-91-7790-297-3 (pdf) Luleå 2019 www.ltu.se Dedicated to my parents and their loved ones. Abstract 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. Table of contents Part I, Introductory chapter 9 Prologue 11 1 Introduction 13 1.1 Art, science and technology 15 1.2 Definitions of loudness 15 1.3 Audio level measurement prior to loudness meters 16 1.4 Present recommendations for audio level alignment in broadcast 18 1.5 The live loudness meter 18 1.6 Differences in the definition of the momentary meter 19 1.7 Collaboration 20 1.8 Motifs and research questions 21 1.9 Overview of thesis 22 2 Studies and publications 23 Study 2013 23 Study 2014 23 Publication 1 23 Publication 2 24 Publication 3 25 Publication 4 26 Publication 5 27 3 Discussion on experimental design 29 3.1 Perspective on evaluation 29 3.2 Overview 31 3.3 Capturing fader data 31 3.4 Other aspects on the experimental design 32 4 Discussion on statistical analysis 35 4.1 Data and experimental factors 35 4.1.1 The parameters 36 Adjustment time and Overshoot 36 Fader movement 37 4.1.2 Experimental factors 38 Element 38 Experience 39 Subjects 39 Trial 40 4.2 Modeling the data 41 The general linear mixed model 41 A screening design 41 Evaluating Live Loudness Meters 5 Summary of results 43 5.1 Results 43 5.1.1 Methodology 43 5.1.2 Evaluation of R 128 45 5.1.3 Evaluation criteria for live loudness meters 46 5.1.4 Evaluation of the momentary time scale ballistics 46 5.1.5 Additional results 47 6 Original contributions 49 6.1 Procedure 49 6.2 Data 49 6.3 Analysis 50 The general linear mixed model 50 Definitions related to ballistics definitions 50 Parameters 51 6.4 Results 51 Time scales and ballistic definitions 51 Meter criteria 52 6.5 Interpretation 52 Suggested links between parameters and evaluation criteria 52 Definitions related to subjective loudness 52 Microdynamics 53 Credits 53 References 53 Errata and clarifications on papers 57 General 57 Publication 1 58 Publication 2 58 Publication 3 59 Publication 4 59 Publication 5 60 Part II, Publications 61 8 Part I Introductory chapter It is the nature of physics to hear the loudest of mouths over the most comprehensive ones. – Criss Jami Prologue There is some truth and wisdom in the above statement. By shouting, you get attention. By playing loud at the concert, you empower the masses. By raising the volume on your portable music player, you get immersed. Loudness is the word to use to describe the sensation of audio intensity, ranging from soft to loud. Loud is a quality—a desirable quality in many cases. It can also be most undesirable in other cases; when your neighbor play the stereo so that the walls tremble; when the motorcycle (not yours) accelerates right beside you on the boardwalk; the scream of undisciplined children when you try to work on a thesis at the coffee house. For terrestrial radio transmissions, loudness has a particular importance. The signal strength of electromagnetic waves decreases with distance and as a consequence of this, so does the signal to noise ratio. By playing louder, you increase the area for which the reception in radio receivers is acceptable. For commercial radio stations, this is very important. Increased area means more potential listeners—means more income from commercials. And as a natural consequence, radio stations play as loud as possible—that is—legally possible. Without governmental restrictions on transmitting power, stations would interfere with each other and the areas for acceptable reception would be reduced for all parts involved. Regulations are formal. Regulations can be deceived—tricked. The commercial stations found out that they could raise the loudness, without actually breaking the regulations for transmitting power. Compressors, multi band compressors and limiters had found their way to a new market. By reducing the dynamics of the audio signal, the average intensity could be raised, and without breaking “the ceiling”. More money to the station. And of course, if the neighboring channel or station has applied these tools, why shouldn’t you? Isn’t there an obvious risk that the consumer would choose the louder channel? Or? You want to keep your job, and maybe go for a raise. So it’s best to play safe. You tell your boss that there are more money to make with these tools. And so the loudness wars began... J. Allan Introduction 1 Introduction With the entry of digital technology in the field of audio engineering, the broadcast industry has encountered new challenges. Issues that was related to analogue signal equipment for processing, storage and transmission, were largely reduced. As an example, the Long Play vinyl format had, in the best of circumstances, around 70 dB in dynamic range (signal to noise ratio or SNR) in consumer pressings [1].
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