User-guided rendering of audio objects using an interactive genetic algorithm

Object-based audio allows for personalisation of content, perhaps to improve accessibility or to increase quality of experience more generally. This paper describes the design and evaluation of an interactive audio renderer, which is used to optimise an audio mix based on the feedback of the listener. A panel of 14 trained participants were recruited to trial the system. The range of audio mixes produced using the proposed system was comparable to the range of mixes achieved using a traditional fader-based mixing interface. Evaluation using the System Usability Scale showed a low level of physical and mental burden, making this a suitable interface for users with impairments, such as vision and/or mobility

Categorisation of distortion profiles in relation to audio quality

Since digital audio is encoded as discrete samples of the audio waveform, much can be said about a recording by the statistical properties of these samples. In this paper, a dataset of CD audio samples is analysed; the probability mass function of each audio clip informs a feature set which describes attributes of the musical recording related to loudness, dynamics and distortion. This allows musical recordings to be classified according to their “distortion character”, a concept which describes the nature of amplitude distortion in mastered audio. A subjective test was designed in which such recordings were rated according to the perception of their audio quality. It is shown that participants can discern between three different distortion characters; ratings of audio quality were significantly different (F(1; 2) = 5:72; p < 0:001; eta^2 = 0:008) as were the words used to describe the attributes on which quality was assessed (�Chi^2(8; N = 547) = 33:28; p < 0:001).This expands upon previous work showing links between the effects of dynamic range compression and audio quality in musical recordings, by highlighting perceptual differences

Variation in multitrack mixes : analysis of low-level audio signal features

To further the development of intelligent music production tools, towards generating mixes that would realistically be created by a human mix-engineer, it is important to understand what kind of mixes can be created, and are typically created, by human mix-engineers. This paper presents an analysis of 1501 mixes, over 10 different songs, created by mix-engineers. The primary dimensions of variation in the full dataset of mixes were ‘amplitude’, ‘brightness’, ‘bass’ and ‘width’, as determined by feature-extraction and subsequent principal component analysis. The distribution of representative features approximated a normal distribution and this is then used to obtain general trends and tolerance bounds for these features. The results presented here are useful as parametric guidance for intelligent music production systems

Herschel/SPIRE observations of water production rates and ortho-to-para ratios in comets

This paper presents Herschel/SPIRE (Spectral and Photometric Imaging Receiver) spectroscopic observations of several fundamental rotational ortho- and para-water transitions seen in three Jupiter-family comets and one Oort-cloud comet. Radiative transfer models that include excitation by collisions with neutrals and electrons, and by solar infrared radiation, were used to produce synthetic emission line profiles originating in the cometary coma. Ortho-to-para ratios (OPRs) were determined and used to derived water production rates for all comets. Comparisons are made with the water production rates derived using an OPR of 3. The OPR of three of the comets in this study is much lower than the statistical equilibrium value of 3; however they agree with observations of comets 1P/Halley and C/2001 A2 (LINEAR), and the protoplanetary disc TW Hydrae. These results provide evidence suggesting that OPR variation is caused by post-sublimation gas-phase nuclear-spin conversion processes. The water production rates of all comets agree with previous work and, in general, decrease with increasing nucleocentric offset. This could be due to a temperature profile, additional water source or OPR variation in the comae, or model inaccuracies

Perception of audio quality in productions of popular music

The quality of recorded music is often highly disputed. To gain insight into the dimensions of quality perception, subjective and objective evaluation of musical programme material, extracted from commercial CDs, was undertaken. It was observed that perception of audio quality and liking of the music can be affected by separate factors. Familiarity with stimuli affected like ratings while quality ratings were most associated with signal features related to perceived loudness and dynamic range compression. The effect of listener expertise was small. Additionally, the sonic attributes describing quality ratings were gathered and indicate a diverse lexicon relating to timbre, space, defects and other concepts. The results also suggest that, while the perceived quality of popular music may have decreased over recent years, like ratings were unaffected