# Dynamic Range Compression and the Semantic Descriptor Aggressive
## 1 Introduction  
### Background  
In addition to general dynamic range control, it is common for music producers to use dynamic range compression (DRC) for colouration and non-linear signal processing techniques, specifically to impart distortion onto program material. Scholarly work has researched DRC use and has shown the industry has developed standard practices which mix engineers implement in their work [1, 2]. One such standard is the use of Universal Audio 1176 (and, under its original name, Urei 1176) as a vocal compressor, particularly when processing vocals in popular music mixes where a specific character or distortion is desirable [3]. Users describe the sound quality of vocals processed in this manner with a number of subjective descriptors. This article investigates one common descriptor, \"aggressive\" to determine what it means at an objective level and answer empirically how an aggressive sound quality can be achieved when using the Universal Audio 1176 (abbreviated to simply 1176) and, more broadly, DRC in vocal productions. The findings will be of use to developers of software and hardware compressors, intelligent mixing algorithms [4, 5] and industry professionals, as the novel results have the potential to change and speed up their workflow. More broadly, the work carried out in this article fills a gap in the research, as little work has been done to get a better understanding of the perceptual effects of dynamic range compression during the mixing stage of music production. Some findings reported in this article were originally presented at an Audio Engineering Society conference [6]. The literature relating to compression in music production has focused mainly on the effects of hyper-compression, often concentrating on whether its artefacts are detrimental to the perceived quality of audio material [7; 8; 9]. [PERSON] and [PERSON] [10] claim that achieving loudness is a significant motivation for using compression, particularly in mastering, so one can argue that this is why hyper-compression is well researched. [PERSON] et al. [11] investigated the audibility of compression artefacts among professional mastering engineers. For the study, twenty mastering engineers undertook an ABX listening experiment to determine whether they could detect artefacts created by limiting. Two songs were processed using the Massey L2007 digital limiter to achieve \(-4\) dB, \(-8\) dB and \(-12\) dB of gain reduction. The masters (including the uncompressed versions) were then presented to the listeners using the ABX method. The results showed that the mastering engineers found it challenging to discern differences between a number of the audio tracks, particularly those with \(-8\) dB of gain reduction and the unprocessed reference. The same experiment carried out by [PERSON] et al. [12] used untrained listeners and showed that they were unable to detect up to \(12\) dB of limiting. [PERSON] et al. [13] had participants rate mixes with compression, which had been introduced at various points in the signal chain, namely on discrete tracks, subgroups and the master stereo buss. Their results showed that listeners preferred mixes where compression had been applied to individual tracks rather than to groups or on the stereo buss. However, their test used identical attack and release settings on all stimuli and made use of the same compressor (Pro Tools Compressor/Limiter), which may have played a role in the results. Adjusting the compressor settings so they were more appropriate for mix buss processing, and using a compressor with a suitable character for buss processing could have yielded a different outcome. [PERSON] and [PERSON] [14] looked into the effect of perceived loudness when using compression on pink noise split into octave bands. For this study, the authors wanted to observe if playback level and crest factor (a measurement of peak to RMS) affected perceived loudness after varying amounts of limiting had been applied.