# Musical Mix Clarity Prediction Using Decomposition and Perceptual Masking Thresholds
###### Abstract  
Objective measurement of perceptually motivated music attributes has application in both target-driven mixing and mastering methodologies and music information retrieval. This work proposes a perceptual model of mix clarity which decomposes a mixed input signal into transient, steady-state, and residual components. Masking thresholds are calculated for each component and their relative relationship is used to determine an overall masking score as the model's output. Three variants of the model were tested against subjective mix clarity scores gathered from a controlled listening test. The best performing variant achieved a Spearman's rank correlation of _rho_ = 0.8382 (_p_ < 0.01). Furthermore, the model output was analysed using an independent dataset generated by progressively applying degradation effects to the test stimuli. Analysis of the model suggested a close relationship between the proposed model and the subjective mix clarity scores particularly when masking was measured using linearly spaced analysis bands. Moreover, the presence of noise-like residual signals was shown to have a negative effect on the perceived mix clarity. mix clarity; clarity; auditory masking; perception; psychoacoustic model; MPEG; music information retrieval +
Footnote †: 2021: 11, 9578. [[https://doi.org/10.3390/app11209578](https://doi.org/10.3390/app11209578)]([https://doi.org/10.3390/app11209578](https://doi.org/10.3390/app11209578))  
perception of the overall quality, as this will depend on the content and intention of the multitrack mix itself. Furthermore, overall quality judgement is likely to be made based upon multiple perceptual features such as loudness [5] and punch [1] alongside that of clarity. Considering the acoustic characteristics of a space, it is possible to objectively determine the clarity and intelligibility that can be achieved. Measures such as C50 (ratio between early and late arriving reflections) and early decay time (EDT) can be combined for this purpose. The direct to reverberant ratio (D/R) has also been linked to acoustic clarity [16]. Furthermore, in a proposal for objective measurement for loudspeaker quality [17], 'clearness' is considered to be a perceptual dimension. This is calculated based on perceived degradation imparted on a signal by the loudspeaker under test in reference to an 'ideal' loudspeaker signal. This approach is similar to established standards to objectively measure music and speech quality, PESQ [18] and PEAQ [19]. These compare encoded signals with their unencoded counterparts to estimate a perceived error signal caused by encoding, which can then be measured using a number of features to determine how disturbing it is. What is common between these measures is that they all compare a signal with an affected version of itself, for example altered by a room or a loudspeaker's response. In the proposed model, there is not a processed version of the signal under test to compare to. Instead, the signal is decomposed and a comparison made between its constituent components to determine if they are suitably balanced. In previous research [20; 21], it has been suggested that masking between signals constituting a multitrack mix could be related to the perception of clarity of the overall mix. Auditory masking is a phenomenon of hearing in which energy present at the ear is not perceived, due to stronger neighbouring energy in frequency or time, known as frequency masking and temporal masking, respectively [22]. The model proposed for mix clarity prediction is based on an analysis of the masking relationship between transient, steady-state, and residual components of the signal, utilising the MPEG Psychoacoustic Model II [23; 24]. The model's performance is assessed using a correlation test against subjective mix clarity scores elicited from a controlled listening test. In addition, further analysis of the model's response to an independent dataset consisting of musical excerpts with varying degrees of controlled degradation is undertaken.