130,446 research outputs found
Measurements of newly defined intensimetric quantities and their physical interpretation
No full textThis paper deals with the measurement and physical interpretation of the quantities a and r introduced in a previous paper [D. Stanzial, N. Prodi, and G. Schiffrer. 'Reactive intensity for general fields and energy polarization,' J. Acoust. Sec. Am. 99, 1868-1876 (1996)]. The quantity a, which has the same time dependence as the squared acoustic pressure arid the same direction as the time averaged sound intensity , will be called here 'radiating' intensity, while r which has zero average, will be called 'oscillating' intensity. A coherent picture of the energy transfer process in steady sound fields based on the decomposition j = a+r of the instantaneous sound intensity will be sketched and discussed. Furthermore, a direct experimental comparison between a and r and the real and imaginary parts of the complex intensity is presented for some field conditions
A novel intensimetric technique for monitoring the radiative properties of sound fields
No full textThe 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 to phase errors
On the Sound Tension and Action reaction Law in Acoustics
No full textAfter 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
Measurement of new energetic parameters for the objective characterization of an opera house
No full textFollowing a rigorous approach to the energetic analysis of sound fields, 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 first 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 through the measurement point. Then, in order to accomplish a complete statistical study of the transient field 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 defined field 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
Reactive acoustic intensity for general fields and energy polarization
No full textA kind of energy polarization is shown to occur in certain acoustic fields, because of energy oscillations due to the instantaneous reactive intensity. The time-averaged behavior of such oscillations is described by a second degree symmetric tensor, which is identified with the time-independent reactive intensity, whose conventional vectorial definition is obtained for particular fields, including monochromatic and spherical ones
Dyad’s consonance and dissonance: combining the compactness and roughness approaches
No full textAt 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
Consonance and dissonance for dyads: combining compactness and roughness
No full textThere are basically two types of approaches that aim to explain on physical grounds the psychoacoustic perception of consonance and dissonance in music. One is based on the “compactness” of the waveform of the combined signal, while the other on the absence of “roughness” induced by beats. In a previous detailed study of each approach for dyads, we found that none of the associated model versions is fully satisfactory when faced to perceptual data, while a surprisingly successful agreement is found by combining the two approaches. In the present contribution, we extend our analysis by exploring how compactness models for dyads can be related to the early arguments by GB Benedetti
On the implementation of quadraphonic data recording
No full textA recent patent in the acoustics field introduced a new approach to quadraphonic data recording and playback. Based on fixed objective criteria, this method seems a promising technique to be used in high-fidelity systems where a characterization of the recording environment is needed. This may be useful for instance when documenting "sound events" such as music performances in real acoustic spaces or when composing virtual acoustic environments as for cinema sound tracks. A major bottleneck for real-time application of this system is represented by the physical implementation, which has to cope both with feasible implementation and no detriment to the high-end performances offered by the quadraphonic technique. This paper presents the architectural design issues for implementation of the quadraphonic recording algorithm: after the algorithm profiling, the hardware/software architecture is derived as a trade-off between complexity, performance and flexibility among different target technologies ranging from Digital Signal Processor (DSP) throughApplication Specific Instruction set Processor (ASIP) up to Field ProgrammableGate Arrays (FPGA) and Application Specific Integrated Circuit (ASIC). As a conclusion, preliminary implementation results for the most promising technology will be provided
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