Interactive Recorded Music: Past, Present and Future

This Engineering Brief charts the story of user-interactivity with recorded music. Audio technologies and creative compositional techniques are discussed with particular regard to scenarios where creativity has driven the demand for technological advance, and vice-versa, where technical advance has enabled new creative-practice approaches. This is contextualized through discussion of relevant implementation in legacy systems, mobile applications, video games, artificial intelligence, and extended realities. In identifying seminal applications of music interactivity from the past and linking them to present capabilities and practices, future trajectories for interactive recorded music are extrapolated

Complex permeability of soft magnetic ferrite polyester resin composites at frequencies above 1 MHz

Composite soft magnetic materials consist of magnetic particles in a non-magnetic matrix. The properties of such materials can be modelled using effective medium theory. Measurements have been made of the complex permeability of composites produced using ferrite powder and polyester resin. The success of various effective medium expressions in predicting the variation of complex permeability with composition has been assessed

Proofs for free - parametricity for dependent types

Reynolds' abstraction theorem shows how a typing judgement in System F can be translated into a relational statement (in second order predicate logic) about inhabitants of the type. We obtain a similar result for pure type systems: for any PTS used as a programming language, there is a PTS that can be used as a logic for parametricity. Types in the source PTS are translated to relations (expressed as types) in the target. Similarly, values of a given type are translated to proofs that the values satisfy the relational interpretation. We extend the result to inductive families. We also show that the assumption that every term satisfies the parametricity condition generated by its type is consistent with the generated logic

A Quantitative Evaluation of Signal Masking in Summed and Compressed Audio

In music production, it is common practice to apply dynamic-range compression to audio signals. Traditionally, the operator’s attention is drawn to the reduction in dynamic range and the sonic signature imposed by the envelope (settings) of the device, and the resulting distortions are familiar to studio practitioners. However, the non-linear characteristics of compression, combined with the interaction of these signals once summed, are likely to produce less familiar side effects, such as intermodulation distortion, manifesting itself as signal masking and other related artefacts. Comparative quantitative analysis of compressed simple and compound signal structures shows the products of this distortion to be realignment of harmonic structure, reduction of spectral and temporal clarity, and rearrangement of dynamic variances related to the rhythmic structure of musical signals. Although the rearrangement of the dynamic variances is expected (in that the variances are reduced), what is less expected is the extent to which amplitudes of certain individual components of summed signals are attenuated, effectively precipitating signal masking. This research shows that decreasing the number of signals interacting with each other whilst applying an equivalent amount of compression can reduce the intermodulation distortion and therefore improve the overall signal quality of commercial music

Evaluating harmonic and intermodulation distortion of mixed signals processed with dynamic range compression

Dynamic range compression of simple signals results in harmonic nonlinear distortion. However, for summed signals, predominantly inharmonic intermodulation distortion (IMD) is generated. This research compares the methods of compressing signals prior to and after summation in order to identify approaches to reduce the level of IMD. Results show that lower IMD values are achieved by applying compression prior to summation

A thin rivulet or ridge subject to a uniform transverse shear stress at its free surface due to an external airflow

We use the lubrication approximation to analyse three closely related problems involving a thin rivulet or ridge (i.e. a two-dimensional droplet) of fluid subject to a prescribed uniform transverse shear stress at its free surface due to an external airflow, namely a rivulet draining under gravity down a vertical substrate, a rivulet driven by a longitudinal shear stress at its free surface, and a ridge on a horizontal substrate, and find qualitatively similar behaviour for all three problems. We show that, in agreement with previous numerical studies, the free surface profile of an equilibrium rivulet/ridge with pinned contact lines is skewed as the shear stress is increased from zero, and that there is a maximum value of the shear stress beyond which no solution with prescribed semi-width is possible. In practice, one or both of the contact lines will de-pin before this maximum value of the shear stress is reached, and so we consider situations in which the rivulet/ridge de-pins at one or both contact lines. In the case of de-pinning only at the advancing contact line, the rivulet/ridge is flattened and widened as the shear stress is increased from its critical value, and there is a second maximum value of the shear stress beyond which no solution with a prescribed advancing contact angle is possible. In contrast, in the case of de-pinning only at the receding contact line, the rivulet/ridge is thickened and narrowed as the shear stress is increased from its critical value, and there is a solution with a prescribed receding contact angle for all values of the shear stress. In general, in the case of de-pinning at both contact lines there is a critical “yield” value of the shear stress beyond which no equilibrium solution is possible and the rivulet/ridge will evolve unsteadily. In an Appendix we show that an equilibrium rivulet/ridge with prescribed flux/area is quasi-statically stable to two-dimensional perturbations

A thin rivulet or ridge subject to a uniform transverse\ud shear stress at its free surface due to an external airflow

We use the lubrication approximation to analyse three closely related problems involving a thin rivulet or ridge (i.e. a two-dimensional droplet) of fluid subject to a prescribed uniform transverse shear stress at its free surface due to an external airflow, namely a rivulet draining under gravity down a vertical substrate, a rivulet driven by a longitudinal shear stress at its free surface, and a ridge on a horizontal substrate, and find qualitatively similar behaviour for all three problems. We show that, in agreement with previous numerical studies, the free surface profile of an equilibrium rivulet/ridge with pinned contact lines is skewed as the shear stress is increased from zero, and that there is a maximum value of the shear stress beyond which no solution with prescribed semi-width is possible. In practice, one or both of the contact lines will de-pin before this maximum value of the shear stress is reached, and so we consider situations in which the rivulet/ridge de-pins at one or both contact lines. In the case of de-pinning only at the advancing contact line, the rivulet/ridge is flattened and widened as the shear stress is increased from its critical value, and there is a second maximum value of the shear stress beyond which no solution with a prescribed advancing contact angle is possible. In contrast, in the case of de-pinning only at the receding contact line, the rivulet/ridge is thickened and narrowed as the shear stress is increased from its critical value, and there is a solution with a prescribed receding contact angle for all values of the shear stress. In general, in the case of de-pinning at both contact lines there is a critical “yield” value of the shear stress beyond which no equilibrium solution is possible and the rivulet/ridge will evolve unsteadily. In an Appendix we show that an equilibrium rivulet/ridge with prescribed flux/area is quasi-statically stable to two-dimensional perturbations

Oil palm in the 2020s and beyond: challenges and solutions

Oil palm, Elaeis guineensis, is by far the most important global oil crop, supplying about 40\\% of all traded vegetable oil. Palm oils are key dietary components consumed daily by over three billion people, mostly in Asia, and also have a wide range of important non-food uses including in cleansing and sanitizing products.info:eu-repo/semantics/publishedVersio