ENGINEERING REPORTS Journal of the Audio Engineering Society Vol. 65, No. 7/8, July/August 2017 ( C  2017) DOI: https://doi.org/10.17743/jaes.2017.0023 The Perception of Hyper-compression by Mastering Engineers MALACHY RONAN, 1 AES Member (Malachy.ronan@ul.ie) , NICHOLAS WARD 1 (Nicholas.ward@ul.ie) , ROBERT SAZDOV, 2 AES Associate Member (rsazdov@gmail.com) , AND HYUNKOOK LEE, 3 AES Member (H.Lee@hud.ac.uk) 1 Digital Media and Arts Research Centre (DMARC), Department of Computer Science and Information Systems, University of Limerick, Ireland 2 University of Technology Sydney (UTS), Australia 3 Applied Psychoacoustics Laboratory (APL), University of Huddersfield, Huddersfield, HD1 3DH, UK Hyper-compressed popular music is the product of a behavior associated with the over-use of dynamic range processing in an effort to gain a competitive advantage in music production. This behavior is unnecessary given the introduction of loudness normalization algorithms across the industry and has been denounced by mastering engineers as generating audible sound quality artifacts. However, the audibility of these sound quality artifacts to mastering engineers has not been examined. This study probes this question using an ABX listening experiment with 20 mastering engineers. On average, mastering engineers correctly discriminated 17 out of 24 conditions suggesting that the sound quality artifacts generated by hyper-compression are difficult to perceive. The findings in the study suggest that audibility depends on the Crest Factor (CF) of the music rather than the amount of CF reduction thus proposing the existence of a threshold of audibility. Further work focusing on education initiatives are offered. 0 INTRODUCTION To create a hyper-compressed popular music record, au- teurs must engage in a behavior compelling them to over- use dynamic range processing. This behavior is influenced by stakeholders and typically occurs at the end of the cre- ative process in an effort to fit the audio signal to the repro- duction medium. However, whilst vinyl had physical lim- itations governing the mastering approach, the limitations of the digital medium relate to perceptual and psycholog- ical ones. Stakeholders’ worry that the laborious creative details will not be perceived in different reproduction en- vironments and that this will influence the success of the record. As a result, the paradigm of loudness maximiza- tion has prevailed in the popular music industry in spite of the introduction of loudness normalization algorithms, such as the ITU BS 1770 [1] and the committed work from proponents of dynamic music. Research on hyper-compression in popular music has been addressed from a number of perspectives: (i) techni- cal [2]–[5], (ii) listener preference [5-7], (iii) sound quality [8–11], (iv) record sales [12,13], and (v) listener fatigue [14,15]. A central theme in these studies is their attempt to reconcile the sound quality judgments communicated by expert listeners with the behavior motivating the practice. In many respects, the loudness wars are a continuation of what Leventhal has termed the “great debate” in audio [17]. This debate relates primarily to the testing of hypotheses posited by audiophiles concerning the audibility of audio compo- nents, sampling rates, and numerous other factors. These hypotheses are typically investigated using discrimination methodologies. Similarly, mastering engineers and expert listeners criticize the sound quality of hyper-compressed music [18] and posit hypotheses concerning the resulting sound quality attributes and their audibility. However, these hypotheses have not been formally tested. The results of a recent ABX experiment suggest that untrained listeners are unable to perceive sound quality ar- tifacts generated by Crest Factor (CF) reductions of up to 10 dB and that this is a primary factor supporting the persis- tence of hyper-compression [19]. Ronan suggests that the prevalence of hyper-compressed music during the loudness wars has altered listeners’ concept of sound quality thus further encouraging the practice in spite of the introduc- tion of loudness normalization [20]. Given the dissonance between the perceptions of mastering engineers and the be- havior of music auteurs, there is a pressing need to examine the audibility of hyper-compression to mastering engineers J. Audio Eng. Soc., Vol. 65, No. 7/8, 2017 July/August 613