Marko Horvat

Physiology-driven adaptive virtual reality stimulation for prevention and treatment of stress related disorders

The significant proportion of severe psychological problems related to intensive stress in recent large peacekeeping operations underscores the importance of effective methods for strengthening the prevention and treatment of stress-related disorders. Adaptive control of virtual reality (VR) stimulation presented in this work, based on estimation of the persons emotional state from physiological signals, may enhance existing stress inoculation training (SIT). Physiology-driven adaptive VR stimulation can tailor the progress of stressful stimuli delivery to the physiological characteristics of each individual, which is indicated for improvement in stress resistance. Following an overview of physiology-driven adaptive VR stimulation, its major functional subsystems are described in more detail. A specific algorithm of stimuli delivery applicable to SIT is outlined.

Comparative analysis of emotion estimation methods based on physiological measurements for real-time applications

In order to improve intelligent Human-Computer Interaction it is important to create a personalized adaptive emotion estimator that is able to learn over time emotional response idiosyncrasies of individual person and thus enhance estimation accuracy. This paper, with the aim of identifying preferable methods for such a concept, presents an experiment-based comparative study of seven feature reduction and seven machine learning methods commonly used for emotion estimation based on physiological signals. The analysis was performed on data obtained in an emotion elicitation experiment involving 14 participants. Specific discrete emotions were targeted with stimuli from the International Affective Picture System database. The experiment was necessary to achieve the uniformity in the various aspects of emotion elicitation, data processing, feature calculation, self-reporting procedures and estimation evaluation, in order to avoid inconsistency problems that arise when results from studies that use different emotion-related databases are mutually compared. The results of the performed experiment indicate that the combination of a multilayer perceptron (MLP) with sequential floating forward selection (SFFS) exhibited the highest accuracy in discrete emotion classification based on physiological features calculated from ECG, respiration, skin conductance and skin temperature. Using leave-one-session-out crossvalidation method, 60.3% accuracy in classification of 5 discrete emotions (sadness, disgust, fear, happiness and neutral) was obtained. In order to identify which methods may be the most suitable for real-time estimator adaptation, execution and learning times of emotion estimators were also comparatively analyzed. Based on this analysis, preferred feature reduction method for real-time estimator adaptation was minimum redundancy - maximum relevance (mRMR), which was the fastest approach in terms of combined execution and learning time, as well as the second best in accuracy, after SFFS. In combination with mRMR, highest accuracies were achieved by k-nearest neighbor (kNN) and MLP with negligible difference (50.33% versus 50.54%); however, mRMR+kNN is preferable option for real-time estimator adaptation due to considerably lower combined execution and learning time of kNN versus MLP.

Assessment of urban soundscapes with the focus on an architectural installation with musical features

Urban soundscapes at five locations in the city of Zadar were perceptually assessed by on-site surveys and objectively evaluated based on monaural and binaural recordings. All locations were chosen so that they would display auditory and visual diversity as much as possible. The unique sound installation known as the Sea Organ was included as an atypical music-like environment. Typical objective parameters were calculated from the recordings related to the amount of acoustic energy, spectral properties of sound, the amount of fluctuations, and tonal properties. The subjective assessment was done on-site using a common survey for evaluating the properties of sound and visual environment. The results revealed the importance of introducing the context into soundscape research because objective parameters did not show significant correlation with responses obtained from interviewees. Excessive values of certain objective parameters could indicate that a sound environment will be perceived as unpleasant or annoying, but its overall perception depends on how well it agrees with peoples expectations. This was clearly seen for the case of Sea Organ for which the highest values of objective parameters were obtained, but, at the same time, it was evaluated as the most positive sound environment in every aspect.

Real-Time Emotional State Estimator for Adaptive Virtual Reality Stimulation

The paper presents design and evaluation of emotional state estimator based on artificial neural networks for physiology-driven adaptive virtual reality (VR) stimulation. Real-time emotional state estimation from physiological signals enables adapting the stimulations to the emotional response of each individual. Estimation is first evaluated on artificial subjects, which are convenient during software development and testing of physiology-driven adaptive VR stimulation. Artificial subjects are implemented in the form of parameterized skin conductance and heart rate generators that respond to emotional inputs. Emotional inputs are a temporal sequence of valence/arousal annotations, which quantitatively express emotion along unpleasant-pleasant and calm-aroused axes. Preliminary evaluation of emotional state estimation is also performed with a limited set of humans. Human physiological signals are acquired during simultaneous presentation of static pictures and sounds from valence/arousalannotated International Affective Picture System and International Affective Digitized Sounds databases.

Reverberation time measuring methods

In this paper different well‐established methods of reverberation time measurement are compared. Furthermore, the results obtained using these methods are compared to the results provided by some additional methods which could serve as an in situ tool if, for any reason, the reverberation time measurements cannot be carried out using the standardized methods. The methods compared in this paper include the standardized methods (EN ISO 3382:2000), namely the impulse response measured with pink noise, exponential sweep, MLS, but also pistol shots of different calibers, balloon bursts, gated external pink noise, and the B&K filtered burst method. In order to make the comparison, the measurements were performed in four acoustically very different spaces ‐ a rather small and well‐damped listening room, a much bigger damped listening room, a rather reverberant atrium, and a large and very reverberant shoebox‐shaped room. The results were evaluated according to signal‐to‐noise ratio criterion as well. Special attention has been given to the influence of room modes on measurement results.

STIMONT: a core ontology for multimedia stimuli description

Affective multimedia documents such as images, sounds or videos elicit emotional responses in exposed human subjects. These stimuli are stored in affective multimedia databases and successfully used for a wide variety of research in psychology and neuroscience in areas related to attention and emotion processing. Although important all affective multimedia databases have numerous deficiencies which impair their applicability. These problems, which are brought forward in the paper, result in low recall and precision of multimedia stimuli retrieval which makes creating emotion elicitation procedures difficult and labor-intensive. To address these issues a new core ontology STIMONT is introduced. The STIMONT is written in OWL-DL formalism and extends W3C EmotionML format with an expressive and formal representation of affective concepts, high-level semantics, stimuli document metadata and the elicited physiology. The advantages of ontology in description of affective multimedia stimuli are demonstrated in a document retrieval experiment and compared against contemporary keyword-based querying methods. Also, a software tool Intelligent Stimulus Generator for retrieval of affective multimedia and construction of stimuli sequences is presented.

Performance evaluation of Websocket protocol for implementation of full-duplex web streams

Besides traditional synchronous HTTP request-response communication paradigm that was used on the Web for decades, modern Web services require more flexible communication system that enables asynchronous messaging between clients and servers, as well as server-initiated data delivery. Among several Web-based asynchronous communication paradigms emerged recently, the Websocket protocol and corresponding Websocket API are accepted as a pivotal framework for implementation of full-duplex asynchronous Web streams. In this paper, we evaluate the performance of the Websocket protocol with respect to underlying TCP protocol. We compare the two against the latency and amount of generated network traffic. The results show that, except a small overhead imposed due to initial handshaking, Websocket-based communication does not consume any more network traffic than plain TCP based communication. However, it is still slightly inferior in terms of latency.

Sound Quality Evaluation of Hand-Held Power Tools

Sound quality evaluation in the context of product sound quality has been addressed and investigated on hand-held power tools. Out of those, power drills, hand-held circular saws and jigsaws have been chosen as the products of interest. A series of listening tests has been conducted in order to ascertain how people perceive not only the sound emitted by these devices in operation, but also certain properties of the devices themselves, such as their quality, safety of handling, robustness, proper functioning and others. The values of objective parameters describing the sounds of these devices were obtained. Well known parameters such as loudness, sharpness and roughness were used, and certain new parameters were defined. Linear regression models were made for subjective parameters describing the perception of the devices using relevant objective parameters as an attempt to model the subjective grades obtained through listening tests and to predict such grades for future products to be included in the investigation. Based on individual parameters, a single-number overall grade was defined.

A comparison of impulse‐like sources to be used in reverberation time measurements

As a part of an extensive ongoing research on reverberation time measurements, efforts have been made to find an impulse‐like source that will comply with certain demands concerning its spectral content and sound pressure levels it can provide. Although the relevant standards state that such kind of sources should be avoided due to the lack of measurement repeatability, their use has proved to be necessary due to inability of conventional omni‐directional loudspeakers to provide adequate sound pressure levels, especially at the low end of the frequency range of interest, thereby ensuring sufficient dynamic range. Therefore, the emphasis of this investigation has been made on peak sound pressure levels and the amount of low frequency content each source is able to provide. The investigated sources include 6 mm and 8 mm pistols, firecrackers with different amount of explosive compound and explosive mixtures of acetylene gas.

Calculating the probability of detecting radio signals from alien civilizations

Although it might not be self-evident, it is in fact entirely possible to calculate the probability of detecting alien radio signals by understanding what types of extraterrestrial radio emissions can be expected and what properties these emissions can have. Using the Drake equation as the obvious starting point, and logically identifying and enumerating constraints of interstellar radio communications can yield the probability of detecting a genuine alien radio signal.