Andreas Floros

Affective acoustic ecology: towards emotionally enhanced sound events

Sound events can carry multiple information, related to the sound source and to ambient environment. However, it is well-known that sound evokes emotions, a fact that is verified by works in the disciplines of Music Emotion Recognition and Music Information Retrieval that focused on the impact of music to emotions. In this work we introduce the concept of affective acoustic ecology that extends the above relation to the general concept of sound events. Towards this aim, we define sound event as a novel audio structure with multiple components. We further investigate the application of existing emotion models employed for music affective analysis to sonic, non-musical, content. The obtained results indicate that although such application is feasible, no significant trends and classification outcomes are observed that would allow the definition of an analytic relation between the technical characteristics of a sound event waveform and raised emotions.

Sound events and emotions: Investigating the relation of rhythmic characteristics and arousal

A variety of recent researches in Audio Emotion Recognition (AER) outlines high performance and retrieval accuracy results. However, in most works music is considered as the original sound content that conveys the identified emotions. One of the music characteristics that is found to represent a fundamental means for conveying emotions are the rhythm-related acoustic cues. Although music is an important aspect of everyday life, there are numerous non-linguistic and nonmusical sounds surrounding humans, generally defined as sound events (SEs). Despite this enormous impact of SEs to humans, a scarcity of investigations regarding AER from SEs is observed. There are only a few recent investigations concerned with SEs and AER, presenting a semantic connection between the former and the listeners triggered emotion. In this work we analytically investigate the connection of rhythm-related characteristics of a wide range of common SEs with the arousal of the listener using sound events with semantic content. To this aim, several feature evaluation and classification tasks are conducted using different ranking and classification algorithms. High accuracy results are obtained, demonstrating a significant relation of SEs rhythmic characteristics to the elicited arousal.

evoDrummer: deriving rhythmic patterns through interactive genetic algorithms

Drum rhythm automatic construction is an important step towards the design of systems which automatically compose music. This work describes a novel mechanism that allows a system, namely the evoDrummer, to create novel rhythms with reference to a base rhythm. The user interactively defines the amount of divergence between the base rhythm and the generated ones. The methodology followed towards this aim incorporates the utilization of Genetic Algorithms and allows the evoDrummer to provide several alternative rhythms with specific, controlled divergence from the selected base rhythm. To this end, the notion of rhythm divergence is also introduced, based on a set of 40 drum---specific features. Four population initialization schemes are discussed and an extensive experimental evaluation is provided. The obtained results demonstrate that, with proper population initialization, the evoDrummer is able to produce a great variety of rhythmic patterns which accurately encompass the desired divergence from the base rhythm.

Stereo Goes Mobile: Spatial Enhancement for Short-distance Loudspeaker Setups

Modern mobile, hand-held devices offer enhanced capabilities for video and sound reproduction. Nevertheless, major restrictions imposed by their limited size render them inconvenient for headset-free stereo sound reproduction, since the corresponding short-distant loudspeakers placement physically narrows the perceived stereo sound localization potential. In this work, we aim at evaluating a spatial enhancement technique for small-size mobile devices. This technique extracts the original panning information from an original stereo recording and spatially extends it using appropriate binaural rendering. A sequence of subjective tests performed shows that the derived spatial perceptual impression is significantly improved in all test cases considered, rendering the proposed technique an attractive approach towards headset-free mobile audio reproduction.

Genetic evolution of L and FL-systems for the production of rhythmic sequences

Music composition with algorithms inspired by nature has led to the creation of systems that compose music with rich characteristics. Nevertheless, the complexity imposed by unsupervised algorithms may arguably be considered as undesired, especially when considering the composition of rhythms. This work examines the composition of rhythms through L and Finite L-systems (FL-systems) and presents an interpretation from grammatical to rhythmic entities that expresses the repetitiveness and diversity of the output of these systems. Furthermore, we utilize a supervised training scheme that uses Genetic Algorithms (GA) to evolve the rules of L and FL-systems, so that they may compose rhythms with certain characteristics. Simple rhythmic indicators are introduced that describe the density, pauses, self similarity, symmetry and syncopation of rhythms. With fitness evaluations based on these indicators we assess the performance of L and FL-systems and present results that indicate the superiority of the FL-system in terms of adaptability to certain rhythmic tasks.

Controlling interactive evolution of 8-bit melodies with genetic programming

Automatic music composition and sound synthesis is a field of study that gains continuously increasing attention. The introduction of evolutionary computation has further boosted the research towards exploring ways to incorporate human supervision and guidance in the automatic evolution of melodies and sounds. This kind of human–machine interaction belongs to a larger methodological context called interactive evolution (IE). For the automatic creation of art and especially for music synthesis, user fatigue requires that the evolutionary process produces interesting content that evolves fast. This paper addresses this issue by presenting an IE system that evolves melodies using genetic programming (GP). A modification of the GP operators is proposed that allows the user to have control on the randomness of the evolutionary process. The results obtained by subjective tests indicate that the utilization of the proposed genetic operators drives the evolution to more user-preferable sounds.

Intelligent Generation of Rhythmic Sequences Using Finite L-systems

Algorithmic music synthesis with intelligent methodologies is a subject of research under both unsupervised and supervised forms, with the production of rhythm being an important aspect of the compositional process. Unsupervised algorithms tend to produce rhythms that are described either as simplistic and repetitive, or very complex and unstable. This work examines a modification of the legacy L-systems that are hereby termed as Finite L-systems (FL-systems). With this modification, the produced symbolic sequences are more controllable, offering a rhythm production alternative that is more flexible than the L-systems. In particular, when used for unsupervised rhythm production, FL-systems construct rhythmic sequences with great variability in terms of complexity and repetitiveness. This trend indicates that their combination with learning algorithms may provide a flexible supervised rhythm production system.

Interactive evolution of 8---bit melodies with genetic programming towards finding aesthetic measures for sound

The efficient specification of aesthetic measures for music as a part of modelling human conception of sound is a challenging task and has motivated several research works. It is not only targeted to the creation of automatic music composers and raters, but also reinforces the research for a deeper understanding of human noesis. The aim of this work is twofold: first, it proposes an Interactive Evolution system that uses Genetic Programming to evolve simple 8---bit melodies. The results obtained by subjective tests indicate that evolution is driven towards more user---preferable sounds. In turn, by monitoring features of the melodies in different evolution stages, indications are provided that some sound features may subsume information about aesthetic criteria. The results are promising and signify that further study of aesthetic preference through Interactive Evolution may accelerate the progress towards defining aesthetic measures for sound and music.

Spatial enhancement for immersive stereo audio applications

In this wok, we propose a stereo recording spatial enhancement technique which retains the original panning / source location, proportionally mapped into the perceived expanded sound stage. The technique uses a time-frequency domain metric for retrieving the panning coefficients applied during the initial stereo mixing. Panning information is also used for separating the original single channel audio streams and finally for synthesizing the expanded sound field using binaural processing. The technique is mainly intended for playback applications over short-distant loudspeaker setups or headphones and, in the context of this work, it is subjectively evaluated in terms of the perceived sound field expansion and the sound-source spatial distribution accuracy.

Wireless Digital Audio Delivery Analysis and Evaluation

Real-time digital wireless playback of CD-quality audio in multipoint setups using quality of service enhancements is analyzed and evaluated in this work. A novel methodology is introduced for simulating wireless digital audio delivery as well as for theoretically deriving the playback distortions. This methodology allows the accurate wireless digital audio delivery and reproduction simulation and leads to significant results for both the wireless networking and audio playback performance, while it provides a framework for defining the optimal parameters for error-free wireless stereo audio reproduction