Papers by Domenico Stanzial
After a brief introduction to the theory and physical interpretation of Lagrangian force density ... more After a brief introduction to the theory and physical interpretation of Lagrangian force density in general sound fields, this article focuses on its stationary average property providing the general expression of the actionreaction law for acoustic fields. This fundamental property allows to define the tension field of sound, which turns out to be easily measured as the gradient of the average potential energy density. The acoustic tension field has been then analytically calculated and visualized for quasi-stationary wave fields and divergent spherical waves. Moreover 2-D graphics comparing the behaviors of sound energy trajectories and tension fields are here reported.
The reconstruction into a cinema hall or a smaller room, of a sound event which has been previous... more The reconstruction into a cinema hall or a smaller room, of a sound event which has been previously recorded in a different acoustical environment is an interesting and still open acoustical problem. A new method for hi-fi multi-channel audio playback based on the general solution of the acoustical inverse problem is here proposed. This is implemented as a general feed-forward redundant control system where the number of acoustical signals to be reconstructed is greater than the number of the control signals feeding one or more loudspeakers working as active boundaries of the virtual playback room. This way an optimal and stable solution via a least square approach is obtained. This control system can be implemented even for complex configurations thanks to acoustic quadraphony: the application of sound intensimetry to audio technology recently developed within the IST-2-511316-IP European project denominated IP-RACINE. After a short explanation of the model theory, the experimental application to the simplest case of 1-D confined field is here presented and some experimentally obtained results are shown.
Lecture Notes in Electrical Engineering, 2013
Recent developments in MEMS technology made available a new class of thermo-resistive sensors to ... more Recent developments in MEMS technology made available a new class of thermo-resistive sensors to be used as functional devices for acoustic particle velocity, v, measurements (Bruschi and Piotto, IEEE Sensors Proceedings 1405–1408, 2011). A very interesting feature of this new generation of v-sensors—distinguishing them from the Microflown® ones (de Bree et al., Sens Actuators A Phys 54:552–557, 1996)—is their compatibility with standard CMOS industrial processes, so allowing to integrate in the same chip both the sensors and read-out electronic circuits. This added flexibility of v-sensors, combined with miniature or MEMS microphones, allows of setting up pressure–velocity (p–v) microprobes for specific applications, in particular when the reduction of production costs is decisive for marketing strategies. In many applications, in fact, carefully designed functional devices can be safely used, without prejudice to the reliability and the robustness of the required measurement process. In other words, the required measurement precision can be achieved despite the low signal-to-noise ratio or limited band frequency response of the used p–v microprobes. This article shows a first comparison between the two kinds of sensors.
Proceedings of Meetings on Acoustics, 2017
On the basis of the algorithms documented in the companion paper 2aSPb1 of Acoustics’17 Boston PO... more On the basis of the algorithms documented in the companion paper 2aSPb1 of Acoustics’17 Boston POMA where the complex intensity is defined and its physical meaning has been described, the block diagram of a possible device for precision measurement of the 3D complex intensity is here proposed. Its outline is based on the spectral equation linking respectively the active and reactive intensity to the real and imaginary part of the wave impedance through a frequency dependent factor given by the autospectrum of the particle velocity (energy-mass equation). In order to estimate the measurement precision of this device, an advanced calibration process requiring three different active and reactive reference fields is included in the layout, and calibration errors obtained with different correction functions in different field conditions are reported.
Proceedings of Meetings on Acoustics, 2017
This paper presents the rigorous definition of acoustic reactivity as a tensor of rank 2, given o... more This paper presents the rigorous definition of acoustic reactivity as a tensor of rank 2, given on the basis of the unique decomposition of particle velocity through the orthogonalization process of acoustic pressure and particle velocity in the Hilbert space of signals. Its spatial representation on the orthonormal basis (Serret-Frenet frame) co-moving with the average energy along any power streamline allows to introduce the concept of "flat" acoustic space, when the streamline has a neglectable curvature and torsion. The complex sound intensity has been accordingly defined as an element S¯ (x) of the complex vector space C 3 tangent to any power streamline at each point x. From this definition a general spectral equation linking the frequency distribution of complex intensity to the wave impedance times the particle velocity autospectrum, has been formulated and called the acoustic energy-mass equation. The graphical proof of the energy-mass equation has been given for two "flat" and one "curved" acoustic spaces built up with quasi-stationary plane waves and divergent spherical waves. This grand result allowed to develop a precision device for measuring 3D sound intensity and its active and reactive spectral components as reported in the companion paper 2aSPb3.
Journal of Sound and Vibration, Mar 1, 2010
ABSTRACT The decay of a steady acoustic field in an enclosure is studied both theoretically and e... more ABSTRACT The decay of a steady acoustic field in an enclosure is studied both theoretically and experimentally. Our main result is that the initial part of any local sound decay is driven by an exponential function of time whose rate constant is equal in modulus to the inverse of the mean energy velocity divergence. This is empirically demonstrated by experimental analysis of both 1-D and 3-D case studies, thus showing that the reverberation time is strictly connected with the sound energy velocity field and can be determined from its differential properties. A further property of the mean energy velocity is found: it is related not only with the reverberation time, but also with the angular momentum density and with the non-uniform distribution of energy.
The concept of 3-D acoustic resistance is here introduced on the basis of energetic properties of... more The concept of 3-D acoustic resistance is here introduced on the basis of energetic properties of a general sound field and its measurement by means of the USP microflown particlevelocity probe is proposed. In the present application a preliminary set of measurements of acoustic pressure and three components of air particle velocity together with the amplitude spectrum of their complex ratio at the open end of an organ pipe is analyzed. Experimental data were collected both when the pipe was playing alone and when the same pipe was playing but coupled at the same fundamental frequency, with a second organ pipe also radiating its own sound nearby the first one. This way the so called "mitnahme" effect was acoustically monitored, and gathered data are here reported and compared. Finally the potentiality of measuring sound resistance in musical acoustics is addressed.
Journal of The Audio Engineering Society, May 1, 1999
The development and application of the intensimetric technique for monitoring the radiative prope... more The development and application of the intensimetric technique for monitoring the radiative properties of sound fields are discussed. The experimental results of three case studies in the areas of room acoustics, musical acoustics, and noise control prove the new technique to be particularly valuable. Special attention is given to the measurement errors of the newly defined component of sound intensity, called oscillating intensity, and to the reliability of the sound intensity meter used. It is shown that the oscillating intensity is almost insensitive tophase errors. ..
InTech eBooks, Mar 6, 2013
From antiquity humanity has sought through scientific enquiry a rational explanation of nature. A... more From antiquity humanity has sought through scientific enquiry a rational explanation of nature. As artworks were considered an imitation of nature, the same purpose has pervaded the history of the arts. The Pythagoreans were the first to put into mathematical terms the rules for aesthetics, borrowing them from music [1]. Later there arose the concepts of eurhythmy or commodulation: the application of rhythmical movements or harmonious proportions in a piece of music; a painting; a sculpture; a building; a dance. Throughout the Middle Ages, mathematical ideas of proportion lived side by side with the body of artistic activity, but during the Renaissance, the natural sciences and mathematics began a process of separation from the arts, both theoretically as well as in practical terms [2]. One of the reasons for the divorce was that all efforts failed to give a rational basis to the rôle played by numerical proportions in the aesthetics of an artwork. This lack of scientific rationale caused a rejection of works on numerical proportion in aesthetics by the scientific community, which began to consider writings in this area esoteric and unscientific. The divergence between arts and sciences grew wider in the twentieth century, with the end of the last movements retaining the ancient mathematical roots of art: neoclassicism and cubism. From this point on, the tendency of artists has been to consider that the mathematical design of an artwork implies an unacceptable constraint to creativity. If, in the future, the gulf between arts and sciences is to be reduced, this may come about through being able to understand in an objective fashion the phenomena that take place in our perceptual and nervous systems when we look at a painting [3], or listen to music. Some of these phenomena may be rooted in the fundamental rôle in the theory of nonlinear dynamical systems played by a particular number: the golden mean.
Lecture notes in electrical engineering, Oct 25, 2013
A novel p–v probe for the measurement of the acoustic impedance is proposed. The device is fabric... more A novel p–v probe for the measurement of the acoustic impedance is proposed. The device is fabricated assembling a micromachined acoustic particle velocity sensor, a commercial microphone, and an electronic read-out interface. The velocity sensor consists of two integrated polysilicon heaters placed over suspended dielectric membranes. The sensor has been designed with a commercial CMOS process and fabricated using a simple post-processing technique. The electronic interface is based on a Wheatstone bridge and a low noise instrumentation amplifier. Preliminary tests confirm the functionality of the proposed probe.
The European Physical Journal Plus
At present, there are two approaches that aim at explaining on physical grounds the psychoacousti... more At present, there are two approaches that aim at explaining on physical grounds the psychoacoustic perception of consonance and dissonance for dyads, whose pioneers have been, respectively, Galilei and Helmholtz: One is based on the “compactness” of the waveform of the combined signal, while the other on the absence of “roughness” due to possible beats. We perform a detailed study of each approach and find that none of the associated model versions, not even the more refined ones, is fully satisfactory when faced to perceptual data on dyads. We show that combining the two approaches results instead in a surprisingly successful agreement with perceptual data: This demonstrates that compactness and roughness are both necessary ingredients for a phenomenological description of consonance and dissonance. Graphical abstract
The Journal of the Acoustical Society of America, 1998
The measurement of a newly discovered property of sound energy, the polarization [Stanzial et al.... more The measurement of a newly discovered property of sound energy, the polarization [Stanzial et al., J. Acoust. Soc. Am. 99, 1868–1876 (1996)], has been carried out for the first time inside an opera house. Since energy polarization is due to the distributions of wavefronts passing through the measurement point, the analysis of this quantity allows one to obtain a precise picture of the effect of sound reflections at the receiving location. The highly symmetric architectural structure of an Italian opera house has been thus investigated at the opening of some boxes and the energy polarization has been compared with the sightline from each box to the stage. Furthermore, a third octave band frequency analysis in the range 100–5000 Hz has been accomplished that allows the visualization of the frequency‐dependent behavior of the reflections’ distribution.
Journal of Sound and Vibration, 2000
Following a rigorous approach to the energetic analysis of sound "elds, the measurement of new qu... more Following a rigorous approach to the energetic analysis of sound "elds, the measurement of new quantities for the physical description of the behavior of sound in enclosed spaces has been carried out inside an Italian opera house. A "rst set of measures has been performed during the steady state, allowing the study of the new discovered property called sound intensity polarization, which accounts for the amount of energy oscillating thorugh the measurement point. Then, in order to accomplish a complete statistical study of the transient "eld behaviour, the full set of quantities involved in the energy continuity equation (total sound energy density and intensity) has been obtained by means of the extension of the classical Schroeder's method to the quantities depending also on the air particle velocity solution of the wave equation. Finally, two newly de"ned "eld indicators, accounting for the local amount of sound energy radiation and the balance between the potential and kinetic parts of the total sound energy density, have been investigated.
Journal of Sound and Vibration, 2010
ABSTRACT The decay of a steady acoustic field in an enclosure is studied both theoretically and e... more ABSTRACT The decay of a steady acoustic field in an enclosure is studied both theoretically and experimentally. Our main result is that the initial part of any local sound decay is driven by an exponential function of time whose rate constant is equal in modulus to the inverse of the mean energy velocity divergence. This is empirically demonstrated by experimental analysis of both 1-D and 3-D case studies, thus showing that the reverberation time is strictly connected with the sound energy velocity field and can be determined from its differential properties. A further property of the mean energy velocity is found: it is related not only with the reverberation time, but also with the angular momentum density and with the non-uniform distribution of energy.
Journal of New Music Research, 2002
Number theory has recently found a quantity of applications in the natural and applied sciences, ... more Number theory has recently found a quantity of applications in the natural and applied sciences, and in particular in the study of nonlinear dynamical systems. As our sensory systems are highly nonlinear, it is natural to suppose that number theory also plays an important rôle in the description of perception, including aesthetics. Here we present a mathematical construction, based on number-theoretical properties of the golden mean, that generates meaningful musical scales of different numbers of notes. We demonstrate that these numbers coincide with the number of notes that an equal-tempered scale must have in order to optimize its approximation to the currently used harmonic musical intervals. Scales with particular harmonic properties and with more notes than the twelve-note scale now used in Western music can be generated. These scales offer interesting new possibilities for artists in the emerging musical world of microtonality and may be rooted in objective phenomena taking place in the nonlinearities of our perceptual and nervous systems.
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Papers by Domenico Stanzial