Abstract: The underwater acoustic sensor network (UASN) is essential for exploration missions and observation in demanding environments. The UASN'S connection route is acoustic waves, which limits its usefulness in comparison to ground sensor networks. This is the case because to its limited capacity, latency, and significant route loss. This article provides comprehensive research of the characteristics of UASN. We explore the functionality of underwater acoustic ad-hoc networks in the presence of disruptions. RF signals are used as a communication mechanism in wireless sensor networks, both terrestrial and aerial. However, in a sub-sea setting, such as deep-sea research, detecting and transmitting data needs a completely different method to underwater communication. The fact that the seas cover 70% of the earth's surface and contain massive amounts of unexplored riches cannot be ignored. The aquatic environment has largely escaped the effects of recent breakthroughs in wireless sensor networks (WSNS) and their broad application in latest studies and economic progress. Research on underwater acoustic sensor networks (UASNS) is developing at a snail's pace due to the difficulties in transferring most of the state-of-the-art of land and air based WSNS to its aquatic equivalent. The bulk of underwater activities rely on acoustic communication and specialized sensors that can endure the harsh environment of the oceans. The purpose of this study is to investigate how UASN works in different situations. End-to-end latency and energy consumption are examined in response to a variety of factors. We also investigate how well underwater acoustic ad-hoc networks perform when nodes are dispersed, and the network is large. Keywords: Under water Acoustics, Sensor, Wireless Sensor Networks, Energy Consumptions.
Current discussions on the objective attributes contributing to concert hall quality started formally in 1962 with the publication of Leo Beranek’s book “Music, Acoustics, and Architecture”. From his consulting work in the late 1950s, Beranek determined that in narrow halls, the short early delay times were an important factor in quality. Needing a measurable acoustical factor, rather than a dimensional one, he chose to define the initial time delay gap (ITDG) for a specific location near the middle of the hall’s main floor. Many acousticians failed to understand the simplicity of this proposal. Beranek had learned that long first delays sounded “arena-like” and “remote”, and, thus, not “intimate”. This bolstered his belief that ITDG was an important objective factor he decided to call “intimacy”. Most acoustical parameters can be directly measured and sensed by the listener, such as reverberation decay, sound strength, clarity. “Intimacy” however is a feeling, and over the past two decades, it has become apparent that it is a multisensory attribute influenced by visual input and perhaps other factors. [J.R. Hyde, Proc. IOA, London, July 2002, Volume 24, Pt. 4, “Acoustical Intimacy in Concert Halls: Does Visual Input affect the Aural Experience”?] Beranek’s paper “Comments on “intimacy” and ITDG concepts in musical performing spaces”, [JASA 115, 2403 (2004)] finally acknowledged the multisensory aspects of “intimacy” and stated this choice of the word “may have been unfortunate”. He further separated the term “intimacy” from ITDG. Documentation of this pronouncement will be provided in the paper.
As the global population ages, residential care facilities are challenged to create positive living environments for people in later life. Health care acoustics are increasingly recognized as a key design factor in the experience of well-being for long-term care residents; however, acoustics are being conceptualized predominantly within the medical model. Just as the modern hospital battles disease with technology, sterility and efficiency, health care acoustics are receiving similar treatment. Materialist efforts towards acoustical separation evoke images of containment, quarantine and control, as if sound was something to be isolated. Sound becomes part of the contested space of long-term care that exists in tension between hospital and home. The move towards acoustical separation denies the social significance of sound in residents’ lives. Sound does not displace care; it emplaces care and the social relationships therein. Drawing upon ethnographic fieldwork in a Canadian long-term care facility, this article will use a phenomenological lens to explore how relationships are shaped in sound among residents living in long-term care. Ethnographic vignettes illustrate how the free flow of music through the care unit incited collective engagement among residents, reduced barriers to sharing social space and constructed new social identity. The article concludes that residents’ relationships are shaped within the acoustical milieu of the care unit and that to impose acoustical separation between residents’ living spaces may further isolate residents who are already at risk of loneliness.
Starting from the observation that the simplest form of forced mechanical oscillation serves as a standard model for analyzing a broad variety of resonance processes in many fields of physics and engineering, the remarkably slow development leading to this insight is reviewed. Forced oscillations and mechanical resonance were already described by Galileo early in the 17th century, even though he misunderstood them. The phenomenon was then completely ignored by Newton but was partly rediscovered in the 18th century, as a purely mathematical surprise, by Euler. Not earlier than in the 19th century did Thomas Young give the first correct description. Until then, forced oscillations were not investigated for the purpose of understanding the motion of a pendulum, or of a mass on a spring, or the acoustic resonance, but in the context of the ocean tides. Thus, in the field of pure mechanics the results by Young had no echo at all. On the other hand, in the 19th century mechanical resonance disasters were observed ever more frequently, e.g. with suspension bridges and steam engines, but were not recognized as such. The equations governing forced mechanical oscillations were then rediscovered in other fields like acoustics and electrodynamics and were later found to play an important role also in quantum mechanics. Only then, in the early 20th century, the importance of the one-dimensional mechanical resonance as a fundamental model process was recognized in various fields, at last in engineering mechanics. There may be various reasons for the enormous time span between the introduction of this simple mechanical phenomenon into science and its due scientific appreciation. One of them can be traced back to the frequently made neglect of friction in the governing equation.
Acoustic characterization of sound absorbing materials requires the measurement of one to five non-acoustical parameters, depending on the assumed impedance model. The measurement of five non-acoustical parameters, in the case of more refined impedance models, is sophisticated and time-consuming. As an alternative, a much simpler measurement of the normal incidence sound absorption in an impedance tube can be carried out, and the non-acoustical parameters can be estimated by minimizing the difference between the measured and modeled absorption curves. This inverse procedure requires the choice of the impedance model and the inversion method. The aim of the article is to review the goodness of simulating annealing for estimating the non-acoustical parameters of Miki and Champoux–Stinson models of two granular absorbers. Three of these non-acoustical parameters, common to the two models, are also measured, so that a comparison between measured and estimated parameters can be performed.
Abstract This paper presents an overview of basic concepts, features and difficulties of the boundary element method (BEM) and examples of its application to exterior and interior problems. The basic concepts of the BEM are explained firstly, and different methods for treating the non-uniqueness problem are described. The application of the BEM to half-space problems is feasible by considering a Green's Function that satisfies the boundary condition on the infinite plane. As a special interior problem, the sound field in an ultrasonic homogenizer is computed. A combination of the BEM and the finite element method (FEM) for treating the problem of acoustic-structure interaction is also described. Finally, variants of the BEM are presented, which can be applied to problems arising in flow acoustics.
Abstract New office buildings use the thermal capacity of the structural mass to provide thermal comfort (TABS). The technique of TABS provides stable thermal conditions in rooms and is perceived to be a long-term energy efficient solution. A priori, this kind of technique is not compatible with traditional acoustic ceilings, covering a room from wall to wall. If the room acoustics is neglected and does not meet the current acoustic standards, this has often enormous impact on the discomfort, cognitive function, absenteeism, satisfaction, the physical well-being as well as the emotional well-being of the occupants. How can we quantify the acoustic and thermal impact of free hanging acoustic solutions on slab's cooling capacity? How does this finding stay in line with new parameters written in the international standard ISO 3382-3 and target values of the upcoming new German guideline VDI 2569? The purpose of this paper is to show the acoustic and thermal tests that have been conducted (6 rooms – Free hanging units (FHU) and baffles), the set-up used (3 timeframes combining 4 scenarios 30%, 45% and 60% coverage with FHU & baffles), the measurement methods and gives data to encourage dialogue and coordination between the acoustician and other building engineering disciplines. The results are giving a clear indication of a much lower impact of high ceiling coverage rates than assumed. In other words, the impact of the users’ behavior on the thermal conditions by e.g. window opening is critical and coverage rates below 60% became secondary.
In Worldwide Automotive market the migration of customers towards cars having fuel efficient ,compact designs is well established & accepted as an engineering challenge by global automotive OEM.OEMs globally continuously trying to meet customer expectations in vehicle performance criterion. Despite moving towards compact, fuel efficient designs, customers are unwilling to lose many of the vehicle attributes. In which NVH performance is major contributing factor which decides the vehicle performance from customer point of view. Hence, the designer has to ensure that the advantages of a significant weight saving is achieved with proper vibro-acoustics performance. This Paper considers some of the research part of using multilayer damping material in automotive BIW for controlling structure born noise. The study deals with the design, design considerations for sandwich Panels. Design CAE validation, and physical testing along with design optimization of a composite sandwich panel. NVH performance is evaluated using a dedicated experimental setup for the vibro-acoustic characterization of sandwich panels. The predicted improvements in NVH behavior of vehicle are considered for further implementation in BIW design.
Optical wavefront can be manipulated by interfering elementary beams with phase inhomogeneity. Therefore a surface allowing huge, abrupt and position-variant phase change would enable all possibilities of wavefront engineering. However, one may not have the luxury of efficient abrupt-phase-changing materials in acoustics. This motivates us to establish a counterpart mechanism for acoustics, in order to empower the wide spectrum of novel acoustic applications. Remarkably, the proposed impedance-governed generalized Snell's law (IGSL) of reflection is distinguished from that in optics. Via the manipulation of inhomogeneous acoustic impedance, extraordinary reflection can be tailored for unprecedented wavefront manipulation while ordinary reflection can be surprisingly switched on or off. Our results may power the acoustic-wave manipulation and engineering. We demonstrate novel acoustic applications by planar surfaces designed with IGSL.
Acoustics are important performance criteria for architecture; however, architects rarely consider them, except, perhaps, when designing concert halls. Architectural spaces can be said to perform well or poorly in terms of their acoustic qualities. By altering the geometry or material characteristics of the surfaces within a room in specific ways, the acoustics can be controlled. Once the geometric rules governing these acoustic alterations are understood, these rules can be encoded into a CAD system through parametric modeling or the use of computer programming. The architectural designer can then generate acoustically regulating surfaces according to desired performance criteria. In this way, acoustic engineering links to architectural design, and allows architectural design to become acoustically performance-driven. This paper considers three primary types of acoustic surfaces: absorbers, resonators, and diffusers. complex surfaces that combine these three performance characteristics in different ways are proposed.