Techniques for the extraction of the impulse response of a linear and time-invariant system.

After a brief overview of the simulation of a linear and time-invariant system through the digital convolution, the paper will start with the description of the various kinds of techniques for the calculation of the impulse response (IR) of the system that has to be simulated. For each technique, and for each signal used for the extraction, we will analyze the positive and negative aspects, then the problems and the advantages that can help the choice of one signal, instead of another, for the simulation of certain kinds of systems. Starting with the IR extraction through the reproduction and recording of the Dirac δ (the impulse function), we will analyze the advantages of this simple technique, and the disadvantages connected with the impossibility of a correct reproduction of the impulse function. The second technique discussed in the paper will be the white and pink noise one: we will reflect on the computational advantages of the FFT algorithm and on the phase problems of pseudo-random noise signals. Then, we will move on to describing the Minimum Length Sequence signal (MLS), the shift register and the XOR for its generation, the extraction of the Dirac δ through the auto-correlation between the original MLS and the one passed through the system, and the problems of this technique, which are strictly linked to the linearity of the system used to measure the IR. At the end, we will talk about the sweep signal: a simple sinusoid, modulated in frequency by an exponential function, seems to be the best method for the extraction of IR from various kinds of systems. The simplicity of the inversion of the sweep signal and its independence from the non-linearities of the measuring system, make this technique the most suitable for the IR calculation of various kinds of systems. A brief example of an IR extraction from a dummy head system (Head Related Impulse Response), should then give the idea of how this technique can be used for the simulation of all kinds of systems, from the old style compressors and equalizers, to the best sounding rooms

Sonification of guidance data during road crossing for people with visual impairments or blindness

In the last years several solutions were proposed to support people with visual impairments or blindness during road crossing. These solutions focus on computer vision techniques for recognizing pedestrian crosswalks and computing their relative position from the user. Instead, this contribution addresses a different problem; the design of an auditory interface that can effectively guide the user during road crossing. Two original auditory guiding modes based on data sonification are presented and compared with a guiding mode based on speech messages. Experimental evaluation shows that there is no guiding mode that is best suited for all test subjects. The average time to align and cross is not significantly different among the three guiding modes, and test subjects distribute their preferences for the best guiding mode almost uniformly among the three solutions. From the experiments it also emerges that higher effort is necessary for decoding the sonified instructions if compared to the speech instructions, and that test subjects require frequent `hints' (in the form of speech messages). Despite this, more than 2/3 of test subjects prefer one of the two guiding modes based on sonification. There are two main reasons for this: firstly, with speech messages it is harder to hear the sound of the environment, and secondly sonified messages convey information about the "quantity" of the expected movement

The creation of a binaural spatialization tool

The main focus of the research presented within this thesis is, as the title suggests, binaural spatialization. Binaural technology and, especially, the binaural recording technique are not particu-larly recent. Nevertheless, the interest in this technology has lately become substantial due to the increase in the calculation power of personal computers, which started to allow the complete and accurate real-time simulation of three-dimensional sound-fields over headphones. The goals of this body of research have been determined in order to provide elements of novelty and of contribution to the state of the art in the field of binaural spatialization. A brief summary of these is found in the following list: • The development and implementation of a binaural spatialization technique with Distance Simulation, based on the individual simulation of the distance cues and Binaural Reverb, in turn based on the weighted mix between the signals convolved with the different HRIR and BRIR sets; • The development and implementation of a characterization process for modifying a BRIR set in order to simulate different environments with different characteristics in terms of frequency response and reverb time; • The creation of a real-time and offline binaural spatialization application, imple-menting the techniques cited in the previous points, and including a set of multichannel(and Ambisonics)-to-binaural conversion tools. • The performance of a perceptual evaluation stage to verify the effectiveness, realism, and quality of the techniques developed, and • The application and use of the developed tools within both scientific and artistic “case studies”. In the following chapters, sections, and subsections, the research performed between January 2006 and March 2010 will be described, outlining the different stages before, during, and after the development of the software platform, analysing the results of the perceptual evaluations and drawing conclusions that could, in the future, be considered the starting point for new and innovative research projects

Haptic Control of Multistate Generative Music Systems

Force-feedback controllers have been considered as a solution to the lack of sonically coupled physical feedback in digital-music interfaces, with researchers focusing on instrument-like models of interaction. However, there has been little research applied to the use of force-feedback interfaces to the control of real-time generative-music systems. This paper proposes that haptic interfaces could enable performers to have a more fully embodied engagement with such systems, increasing expressive control and enabling new compositional and performance potentials. A proof-of-concept project is described, which entailed development of a core software toolkit and implementation of a series of test cases

The architecture and development of multi-role course design of a web-based group training system

Due to the fast development of information technology there are new opportunities for traditional training systems. Many e-training systems are proposed and implemented, however, there is rarely any research on group based e-training system that allow people to train in a group that involves different roles. This paper proposes an architecture for a web based surgery group training system that supports multi-role group training courses. A course model based on XPDL (XML Process Definition Language) is introduced to bridge the understanding of a graphical multi-role course design and the computer application. There is also an explanation on how the multi-role courses are designed and used in applications. Finally a demonstration experiment is given

Reverberation and its Binaural Reproduction: The Trade-off between Computational Efficiency and Perceived Quality

Accurately rendering reverberation is critical to produce realistic binaural audio, particularly in augmented reality applications where virtual objects must blend in seamlessly with real ones. However, rigorously simulating sound waves interacting with the auralised space can be computationally costly, sometimes to the point of being unfeasible in real time applications on resource-limited mobile platforms. Luckily, knowledge of auditory perception can be leveraged to make computational savings without compromising quality. This chapter reviews different approaches and methods for rendering binaural reverberation efficiently, focusing specifically on Ambisonics-based techniques aimed at reducing the spatial resolution of late reverberation components. Potential future research directions in this area are also discussed

Audio Tactile Maps (ATM) System for the Exploration of Digital Heritage Buildings by Visually-impaired Individuals - First Prototype and Preliminary Evaluation

P.I. Dr. Lorenzo Piccinali, Faculty of Technology, DMUNavigation within historic spaces requires analysis of a variety of acoustic, proprioceptive and tactile cues; a task that is well-developed in many visually-impaired individuals but for which sighted individuals rely almost entirely on vision. For the visually-impaired, the creation of a cognitive map of a space can be a long process for which the individual may repeat various paths numerous times. While this action is typically performed by the individual on-site, it is of some interest to investigate to what degree this task can be performed off-site using a virtual simulator. We propose a tactile map navigation system with interactive auditory display. The system is based on a paper tactile map upon which the user’s hands are tracked. Audio feedback provides; (i) information on user-selected map features, (ii) dynamic navigation information as the hand is moved, (iii) guidance on how to reach the location of one hand (arrival point) from the location of the other hand (departure point) and (iv) additional interactive 3D-audio cues useful for navigation. This paper presents an overview of the initial technical development stage, reporting observations from preliminary evaluations with a blind individual. The system will be beneficial to visually impaired visitors to heritage sites; we describe one such site which is being used to further assess our prototype