Download Digital guitar body mode modulation with one driving parameter In this study we have developed a digital guitar body mode modulation technique where the modulation can be controlled through one driving parameter. The filtering and modulation is done with frequency-warped recursive filters that have been implemented in real-time on a modern DSP processor. By changing the warping parameter the perceived size of the body can be controlled, by a pedal or automatically, resulting in an interesting effect. This effect is useful both for the electric and the amplified acoustic guitar. Perceptual properties of the effect are studied by a listening experiment. (See also www.acoustics.hut.fi/demo/dafx2000-bodymod/)
Download Model-based synthesis and transformation of voiced sounds In this work a glottal model loosely based on the Ishizaka and Flanagan model is proposed, where the number of parameters is drastically reduced. First, the glottal excitation waveform is estimated, together with the vocal tract filter parameters, using inverse filtering techniques. Then the estimated waveform is used in order to identify the nonlinear glottal model, represented by a closedloop configuration of two blocks: a second order resonant filter, tuned with respect to the signal pitch, and a regressor-based functional, whose coefficients are estimated via nonlinear identification techniques. The results show that an accurate identification of real data can be achieved with less than regressors of the nonlinear functional, and that an intuitive control of fundamental features, such as pitch and intensity, is allowed by acting on the physically informed parameters of the model. 10
Download An auditorily motivated analysis method for room impulse responses In this paper a new auditorily motivated analysis method for room impulse responses is presented. The method applies same kind of time and frequency resolution than the human hearing. With the proposed method it is possible to study the decaying sound field of a room in more detail. It is applicable as well in the analysis of artificial reverberation and related audio effects. The method, used with directional microphones, gives us also hints about the diffuseness and the directional characteristics of the sound fields in the time-frequency domain. As a case study two example room impulse responses are analyzed.
Download Transaural 3-D audio with user-controlled calibration A calibration method allowing users to customize the loudspeaker layout for 2-, 4-, and 5.1-channel playback, and to steer the “sweet spot” to the position o f the listener’s head is presented. The method, which is applied to a computationally efficient transaural 3D audio system for dynamic spatialization o f multiple sound sources, is based on u ser interaction and auditory feedback. The robustness of the a uditory sensation is analyzed for small displacements of the listener near the sweet spot. A modification of the system permits continuous adjustment of the sweet spot size by the listener. The modification limits the a rtifacts due to the transaural processing for positions away from the sweet spot. For wide settings, the system gradually reduces to a discrete amplitude panning system.
Download A reverberator based on absorbent all-pass filters Artificial reverberator topologies making use of all-pass filters in a feedback loop are popular, but have lacked accurate control of decay time and energy level. This paper reviews a general theory of artificial reverberators based on Unitary-Feedback Delay Networks (UFDN), which allow accurate control of the decay time at multiple frequencies in such topologies. We describe the design of an efficient reverberator making use of chains of elementary filters, called “absorbent all-pass filters”, in a feedback loop. We show how, in this particular topology, the late reverberant energy level can be controlled independently of the other control parameters. This reverberator uses the I3DL2 control parameters, which have been designed as a standard interface for controlling reverberators in interactive 3D audio.
Download A parallel 3D digital wave guide mesh model with tetrahedral topology for room acoustic simulation Following a summary of the basic principles of 3D waveguide mesh modelling and the context of its application to room acoustic simulation, this paper presents a detailed analysis of the tetrahedral mesh topology and describes its implementation on a parallel computer model. Its structural characteristics are analysed, with particular emphasis on how they influence execution speed. Performance deterioration due to communication overhead in the parallelised model is discussed. Theoretical predictions are compared with data from performance tests carried out on different computer platforms and both are contrasted with the corresponding results from the rectilinear model, in order to assess the practical efficiency of the model. Objective validation tests are reported and discussed.
Download Multi-loudspeaker reverberation system In this paper we present a reverberation system based on a multiloudspeaker configuration. The aim of this work is to produce a natural sounding reverberation system with a similar pattern to the produced in real rooms. A new method for sound spatialization is presented, and it is used to locate on the virtual room’s surfaces the early reflections produced in a reverberant space. Each loudspeaker is fed with its corresponding early reflection sequence after the panning process, and an artificial late reverberation is added in each channel, obtaining a more realistic experience that the obtained with other artificial reverberation systems.
Download Enhanced 3D sound field synthesis and reproduction system by compensating interfering reflections The antique stereophonic recording and playback format is going to be replaced by new surround sound formats in the near future. At the moment, various surround techniques are being investigated in many artistic and technical applications. The main concern is to find an appropriate recording and playback format which supports the natural spatial hearing cues. Therefore, surround sound systems should provide a homogeneous and coherent sound field image, both for recorded and synthesized sound fields [1]. In a homogeneous sound reproduction system, no direction is treated preferentially. Coherent sound field image means that the image remains stable under changes of the listener position, though the image may change as a natural sound field does. The Holophony and Ambisonic system described by Nicol and Emerit [2] is the basic approach. This system will be extended by a new approach to compensate the interfering reflections of the reproduction room. Further possibilities to determine higher order Ambisonic signals using the beam forming approach are investigated.