1,721,041 research outputs found
Signal-theoretic characterization of waveguide mesh geometries for models of two-dimensional wave propagation in elastic media
No full textWaveguide meshes are efficient and versatile models of wave propagation along a multidimensional ideal medium. The choice of the mesh geometry affects both the computational cost and the accuracy of simulations. In this paper, we focus on two-dimensional (2-D) geometries and use multidimensional sampling theory to compare the square, triangular, and hexagonal meshes in terms of sampling efficiency and dispersion error under conditions of critical sampling. The analysis shows that the triangular geometry exhibits the most desirable tradeoff between accuracy and computational cos
A quantum vocal theory of sound
Full text linkConcepts and formalism from acoustics are often used to exemplify quantum mechanics. Conversely, quantum mechanics could be used to achieve a new perspective on acoustics, as shown by Gabor studies. Here, we focus in particular on the study of human voice, considered as a probe to investigate the world of sounds. We present a theoretical framework that is based on observables of vocal production, and on some measurement apparati that can be used both for analysis and synthesis. In analogy to the description of spin states of a particle, the quantum-mechanical formalism is used to describe the relations between the fundamental states associated with phonetic labels such as phonation, turbulence, and supraglottal myoelastic vibrations. The intermingling of these states, and their temporal evolution, can still be interpreted in the Fourier/Gabor plane, and effective extractors can be implemented. The bases for a quantum vocal theory of sound, with implications in sound analysis and design, are presented
Physical Modeling of Membranes for Percussion Instruments
No full textRecent research on Physical Modeling has led to 2-D discrete-time structures based on the Digital Waveguides. These structures are well suited for efficient yet accurate simulation of wave propagation in an ideal membrane. Nevertheless, real membranes exhibit a different behaviour, due to the environmental conditions and to the material they are made of. In this work we consider some aspects, crucial for the audio signal, of the physical phenomena concerning real membranes, and we will develop a 2-D waveguide model encompassing the effects of these aspects. In order to excite the simulated membrane, we will consider a hammer model previously developed for piano strings, and here adapted to fit the hammer-membrane interaction
Auditory distance perception in an acoustic pipe
No full textIn a study of auditory distance perception, we investigated the effects of exaggeration the acoustic cue of reverberation where the intensity of sound did not vary noticeably. The set of stimuli was obtained by moving a sound source inside a 10.2-m long pipe having a 0.3-m diameter. Twelve subjects were asked to listen to a speech sound while keeping their head inside the pipe and then to estimate the egocentric distance from the sound source using a magnitude production procedure. The procedure was repeated eighteen times using six different positions of the sound source. Results show that the point at which perceived distance equals physical distance is located approximately 3.5 m away from the listening point, with an average range of distance estimates of approximately 3.3 m, i.e., 1.65 to 4.9 m. The absence of intensity cues makes the acoustic pipe a potentially interesting modeling paradigm for the design of auditory interfaces in which distance is rendered independently of loudness. The proposed acoustic environment also confirms the known unreliability of certain distance cues
Numerical methods for a nonlinear impact model: A comparative study with closed-form corrections
Full text linkA physically based impact modelalready known and exploited in the field of sound synthesis-is studied using both analytical tools and numerical simulations. It is shown that the Hamiltonian of a physical system composed of a mass impacting on a wall can be expressed analytically as a function of the mass velocity during contact. Moreover, an efficient and accurate approximation for the mass outbound velocity is presented, which allows to estimate the Hamiltonian at the end of the contact. Analytical results are then compared to numerical simulations obtained by discretizing the system with several numerical methods. It is shown that, for some regions of the parameter space, the trajectories of the discretized systems may significantly drift from the analytically derived curves. Two approaches, based on enforcing numerical energy consistency, are then proposed to improve the accuracy of numerical simulation
Importance of force feedback for following uneven virtual paths with a stylus
No full textIt is commonly known that a physical textured path can be followed by indirect touch through a probe also in absence of vision if sufficiently informative cues are delivered by the other sensory channels, but prior research indicates that the level of performance while following a virtual path on a touchscreen depends on the type and channel such cues belong to. The re-enactment of oriented forces, as they are induced by localized obstacles in probe-based exploration, may be important to equalize the performance between physical and virtual path following. Using a stylus attached to a force-feedback arm, an uneven path marked by virtual bars was traversed while time and positions were measured under normal sensory conditions, as well as in absence of vision or hearing. Alternatively, participants followed the same path on a wooden tablet provided with physical bars in relief (i.e., without receiving synthetic force) under the same conditions. The visual conditions were found to be significantly faster than the non-visual conditions. However, there was no significant advantage of traversing either path. In contrast to previous experiments in which the virtual bars were rendered using vibrotactile and/or auditory cues, comparable times to traverse the physical and virtual path were found also when vision was disabled. Our results hence suggest that users who are deprived of vision follow textured virtual paths as efficiently as physical paths, if unevenness is rendered using restorative force cues through a stylus
Sing and Measure: Sound as Voice as Quanta
No full textThe universal concept of a “music of the spheres” traverses the history of philosophy, science and art, from Pythagoras to Kepler and beyond. In modern times, a sphere in three dimensions—the Bloch sphere—is used to illustrate the state of a qubit, the basic unit of quantum information. On the same spherical surface, the fundamental components of voice production can be located, so that any utterance can be seen as the evolution of a unit two-dimensional vector having complex coefficients. Indeed, any sound can be analyzed and decomposed into overlapping sinusoidal components, broadband noises, and impulsive transients, which in turn can be associated to fundamental means of vocal sound production, such as phonation, turbulence, and slow myoelastic vibrations or pulses. The quantum sphere can be made to sing the universal sound
Linearizing Auditory Distance Estimates by Means of Virtual Acoustics
Full text linkAuditory distance estimates are not linearly related to physical distances: people tend to overestimate close physical distances, and underestimate far distances. We have modeled a virtual listening environment whose objective is to provide a linear relationship between perceived and physical distance. The simulated environment consists of a trapezoidal membrane with specific absorbing properties at the boundaries. A physics-based model simulates acoustic wave propagation in this virtual space and provides auditory distance cues, namely intensity and direct-to-reverberant energy ratio. Simulations predict the linearity of the psychophysical function relating physical distance to perceived distance, computed from Bronkhorst and Houtgast's model. A listening experiment, involving eleven subjects and using a procedure inspired by the MUSHRA test, shows that the individual psychophysical functions are well described by a linear fit. This promising result suggests that the present virtual environment is a potential tool for providing a direct mapping between perceived and physical distance in auditory interfaces. In addition, the procedure was validated by retesting the same stimuli with the magnitude estimation method as well as reproducing the modified version of the MUSHRA test on a different simulated environment geometry
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