scholarly journals Do Leonardo Da Vinci’s Drawings, Room Acoustics And Radio Astronomy Have Anything In Common?

2022 ◽  
Author(s):  
Andrzej Kulowski
Keyword(s):  
Light Propagation ◽  
Sound Field ◽  
Analytical Description ◽  
Energy Concentration ◽  
Room Acoustics ◽  
Spherical Mirror ◽  
Small Fragment ◽  
Radio Telescopes ◽  
Distant Source ◽  
Energy Relations

Abstract After introducing Leonardo da Vinci’s (LdV) predecessors in the field of light propagation research, his drawings on the topic of focussing light through a spherical mirror are analysed. The discovery of LdV is presented, according to which, at an infinitely distant source of rays, a small fragment of the canopy is enough to generate a focus, while the rest of the mirror forms caustics for which LdV did not indicate an application. An analytical description of the energy concentration in the focus and on the caustics is given, together with its reference to the geometric representation of the acoustic field in rooms. Using symmetry in the description of energy relations in acoustics and electromagnetism, the interference that occurs on the caustics produced by the acoustic and electromagnetic wave is discussed. It is explained why in the sound field in existing halls, instead of a whole caustic only its cusp is observed, which is perceived as a point-like sound focus. The size of the mirror aperture, shown graphically by LdV, is determined. How the development of receiving techniques increased the mirror aperture compared to the LdV estimate is also shown. The implementation of these improvements is presented via the example of the Arecibo and FAST radio telescopes.

General Theory of the Energy Relations in Halls with Asymmetrical Absorption

1998 ◽  
Vol 5 (3) ◽  
pp. 163-183 ◽  
Author(s):  
Higini Arau
Keyword(s):  
General Theory ◽  
Uniform Distribution ◽  
Decay Time ◽  
Sound Field ◽  
Reverberation Time ◽  
Sound Energy ◽  
Method Of Calculation ◽  
New Energy ◽  
Energy Relations

In this paper we describe a method of calculation of the energy relations in halls where the existence of a non-uniform distribution of absorptive material in the room results in a non-diffuse sound field. The cases of halls used for concerts and speech have both been treated in order to derive new energy relations that yield known expressions when applied to a diffuse sound field. The importance of the initial reverberation time corresponding to the first portion of the decay has been verified showing that the main subjective parameters relating to the sound energy are influenced strongly by this portion, which is called the Early Decay Time if it is measured in the first 10 dB of the decay.

Quantifying Non-Linearity in Early Decay Curves of Measured and Computer-Modeled Room Impulse Responses of a Highly Non-Diffuse Room Exhibiting Flutter Echo

2020 ◽  
Author(s):  
Heather L. Lai ◽  
Brian Hamilton
Keyword(s):  
Linear Regression ◽  
Computer Modeling ◽  
Impulse Response ◽  
Decay Curve ◽  
Sound Field ◽  
Energy Decay ◽  
Room Acoustics ◽  
Reverberation Time ◽  
Sound Fields ◽  
Regression Curves

Abstract This paper investigates the use of two room acoustics metrics designed to evaluate the degree to which the linearity assumptions of the energy density curves are valid. The study focuses on measured and computer-modeled energy density curves derived from the room impulse response of a space exhibiting a highly non-diffuse sound field due to flutter echo. In conjunction with acoustical remediation, room impulse response measurements were taken before and after the installation of the acoustical panels. A very dramatic decrease in the reverberation time was experienced due to the addition of the acoustical panels. The two non-linearity metrics used in this study are the non-linearity parameter and the curvature. These metrics are calculated from the energy decay curves computed per octave band, based on the definitions presented in ISO 3382-2. The non-linearity parameter quantifies the deviation of the EDC from a straight line fit used to generated T20 and T30 reverberation times. Where the reverberation times are calculated based on a linear regression of the data relating to either −5 to −25 dB for T20 or −5 to −35 dB for T30 reverberation time calculations. This deviation is quantified using the correlation coefficient between the energy decay curve and the linear regression for the specified data. In order to graphically demonstrate these non-linearity metrics, the energy decay curves are plotted along with the linear regression curves for the T20 and T30 reverberation time for both the measured data and two different room acoustics computer-modeling techniques, geometric acoustics modeling and finite-difference wave-based modeling. The intent of plotting these curves together is to demonstrate the relationship between these metrics and the energy decay curve, and to evaluate their use for quantifying degree of non-linearity in non-diffuse sound fields. Observations of these graphical representations are used to evaluate the accuracy of reverberation time estimations in non-diffuse environments, and to evaluate the use of these non-linearity parameters for comparison of different computer-modeling techniques or room configurations. Using these techniques, the non-linearity parameter based on both T20 and T30 linear regression curves and the curvature parameter were calculated over 250–4000 Hz octave bands for the measured and computer-modeled room impulse response curves at two different locations and two different room configurations. Observations of these calculated results are used to evaluate the consistency of these metrics, and the application of these metrics to quantifying the degree of non-linearity of the energy decay curve derived from a non-diffuse sound field. These calculated values are also used to evaluate the differences in the degree of diffusivity between the measured and computer-modeled room impulse response. Acoustical computer modeling is often based on geometrical acoustics using ray-tracing and image-source algorithms, however, in non-diffuse sound fields, wave based methods are often able to better model the characteristic sound wave patterns that are developed. It is of interest to study whether these improvements in the wave based computer-modeling are also reflected in the non-linearity parameter calculations. The results showed that these metrics provide an effective criteria for identifying non-linearity in the energy decay curve, however for highly non-diffuse sound fields, the resulting values were found to be very sensitive to fluctuations in the energy decay curves and therefore, contain inconsistencies due to these differences.

The Physics of Music

2012 ◽  
pp. 29-47
Author(s):  
Jyri Pakarinen
Keyword(s):  
Sound Transmission ◽  
Sound Field ◽  
Room Acoustics ◽  
Human Observer ◽  
Sound Sources ◽  
Acoustic Effect ◽  
Musical Sound ◽  
Transmission Parameters ◽  
Definition Of ◽  
Physical Phenomena

This chapter discusses the central physical phenomena involved in music. The aim is to provide an explanation of the related issues in an understandable level, without delving unnecessarily deep in the underlying mathematics. The chapter is divided in two main sections: musical sound sources and sound transmission to the observer. The first section starts from the definition of sound as wave motion, and then guides the reader through the vibration of strings, bars, membranes, plates, and air columns, that is, the oscillating sources that create the sound for most of the musical instruments. Resonating structures, such as instrument bodies are also reviewed, and the section ends with a discussion on the potential physical markup parameters for musical sound sources. The second section starts with an introduction to the basics of room acoustics, and then explains the acoustic effect that the human observer causes in the sound field. The end of the second section provides a discussion on which sound transmission parameters could be used in a general music markup language. Finally, a concluding section is presented.

Active Acoustic Systems for the Control of Room Acoustics

2011 ◽  
Vol 18 (3-4) ◽  
pp. 237-258 ◽  
Author(s):  
M. A. Poletti
Keyword(s):  
Subjective Experience ◽  
Sound Field ◽  
Acoustic Properties ◽  
Room Acoustics ◽  
Live Performance ◽  
Acoustic Parameters ◽  
Active Systems ◽  
Acoustic Design ◽  
Boundary Properties ◽  
Passive Acoustic

The acoustic design of auditoria involves the specification of the room geometry and boundary properties, and any additional acoustic elements such as reflectors or diffusers, to usefully direct sound to produce a desired subjective experience, quantified by measurable acoustic parameters. This design must take into account the reflection of sound within the stage area, the early reflections from the stage to the audience and the reverberant response of the room. The sound produced by the audience can also be an important consideration. Active acoustic systems provide an alternative approach to controlling subjective experience. They use microphones, electronic processors and loudspeakers to create reflections and reverberation in addition to those produced by the naturally-occurring sound field. The acoustic properties can be changed instantly, and the enhanced acoustic properties of the auditorium can typically be varied over a wider range than can be produced by variable passive techniques. The design of active acoustics follows that of passive approaches, but rather than the physical arrangement of the room surfaces, it commences with an existing passive space with some minimum acoustic condition, and requires the arrangement of microphones to detect relevant sound and the choice of processors and loudspeaker positions to direct it usefully back into the room to produce a desired set of acoustic parameters. While active systems have historically been developed with the goal of enhancing either the stage or audience sound, they must generally provide the same control of sound as passive acoustic design. This paper discusses the principles of active acoustic systems and how they are used to achieve the required range of control. A survey of current commercial systems is given and some implications for the future of live performance are explored.

Diffusion Equation-Based Finite Element Modeling of a Monumental Worship Space

2017 ◽  
Vol 25 (04) ◽  
pp. 1750029 ◽  
Author(s):  
Zühre Sü Gül ◽  
Ning Xiang ◽  
Mehmet Çalışkan
Keyword(s):  
Finite Element ◽  
Diffusion Equation ◽  
Geometric Model ◽  
Three Dimensional ◽  
Sound Field ◽  
Equation Model ◽  
Field Analysis ◽  
Room Acoustics ◽  
Sound Energy ◽  
Worship Space

In this work, a diffusion equation model (DEM) is applied to a room acoustics case for in-depth sound field analysis. Background of the theory, the governing and boundary equations specifically applicable to this study are presented. A three-dimensional geometric model of a monumental worship space is composed. The DEM is solved over this model in a finite element framework to obtain sound energy densities. The sound field within the monument is numerically assessed; spatial sound energy distributions and flow vector analysis are conducted through the time-dependent DEM solutions.

Directional sound field decay analysis in performance spaces

2021 ◽  
pp. 1351010X2098462
Author(s):  
Marco Berzborn ◽  
Michael Vorländer
Keyword(s):  
Temporal Evolution ◽  
Sound Field ◽  
General Purpose ◽  
Room Acoustics ◽  
Complex Geometries ◽  
Sound Fields ◽  
Temporal Features ◽  
Spatio Temporal ◽  
Field Decay ◽  
Late Part

The analysis of the spatio-temporal features of sound fields is of great interest in the field of room acoustics, as they inevitably contribute to a listeners impression of the room. The perceived spaciousness is linked to lateral sound incidence during the early and late part of the impulse response which largely depends on the geometry of the room. In complex geometries, particularly in rooms with reverberation reservoirs or coupled spaces, the reverberation process might show distinct spatio-temporal characteristics. In the present study, we apply the analysis of directional energy decay curves based on the decomposition of the sound field into a plane wave basis, previously proposed for reverberation room characterization, to general purpose performance spaces. A simulation study of a concert hall and two churches is presented uncovering anisotropic sound field decays in two cases and highlighting implications for the resulting temporal evolution of the sound field diffuseness.

Classroom Acoustics

1996 ◽  
Vol 27 (1) ◽  
pp. 16-20 ◽  
Author(s):  
Frederick S. Berg ◽  
James C. Blair ◽  
Peggy V. Benson
Keyword(s):  
Teaching And Learning ◽  
Noise Control ◽  
Sound Field ◽  
Room Acoustics ◽  
Signal Control ◽  
American Education ◽  
Acoustical Parameters ◽  
Classroom Acoustics ◽  
What Is Said ◽  
Field Amplification

Classroom acoustics are generally overlooked in American education. Noise, echoes, reverberation, and room modes typically interfere with the ability of listeners to understand speech. The effect of all of these acoustical parameters on teaching and learning in school needs to be researched more fully. Research has shown that these acoustical problems are commonplace in new as well as older schools, and when carried to an extreme, can greatly affect a child's ability to understand what is said (Barton, 1989; Blair, 1990; Crandell, 1991; Finitzo, 1988). The precise reason for overlooking these principles needs to be studied more fully. Recently, however, acoustic principles have been clarified, and technologies for measuring room acoustics and providing sound systems have become available to solve many of the acoustical problem in classrooms (Berg, 1993; Brook, 1991; D'Antonio, 1989; Davis & Davis, 1991; Davis & Jones, 1989; Eargle, 1989; Egan, 1988; Everest, 1987, 1989; Foreman, 1991; Hedeen, 1980). This article describes parameters of the problem, its impact on students and teachers, and four possible solutions to the problem. These solutions are noise control, signal control without amplification, individual amplification systems, and sound field amplification systems.

On the Acoustics of Auditoria

1994 ◽  
Vol 1 (1) ◽  
pp. 27-48 ◽  
Author(s):  
H. Kuttruff
Keyword(s):  
Sound Propagation ◽  
Sound Field ◽  
Great Benefit ◽  
Room Acoustics ◽  
Short Introduction ◽  
New Developments ◽  
Sound Fields ◽  
Field Simulation ◽  
Basic Facts

The paper presents a short introduction into auditorium acoustics and reports on a few new developments in this field, which are believed to be of great benefit both for the acoustical design of auditoria and for research in practical room acoustics. The first part describes in a rather elementary way the basic facts of sound propagation in enclosures, including the effects of reflections and the role of reverberation. Furthermore, some of the numerous objective parameters are discussed which have been introduced in order to characterize particular aspects of sound fields. In the second part, recently developed methods of sound field simulation are described by which such parameters can be predicted. Methods of “auralization” are briefly discussed by which aural impressions from non-existing halls can be created on the basis of digital sound field simulation.

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