Acoustics

The use of sonar by military vessels during military exercises may produce acoustic pollution of the marine environment. States have an obligation under international law to reduce and control this form of pollution. Regulation of the use of sonar is rendered more complex by the specific regime applicable to warships, i.e. sovereign immunity. Immunity however does not prevent in all cases action by States other than the flag State, notwithstanding the limitations imposed by Art. 236 of the United Nations Convention on the Law of the Sea. More importantly, immunity does not prevent the flag State from taking measures to reduce pollution caused by its own warships. Under some environmental treaties, flag States not only may, but have the obligation to adopt measures.

Natural materials are becoming a valid alternative to traditional synthetic ones for sound absorption
treatments. In particular, in recent years, natural fibers have been considered valid raw materials for
producing sound absorbing panels at a reduced cost. Moreover, these fibers often have good thermal
insulation properties, have no harmful effects on health, and are available in large quantities often as a
waste product of other production cycles. Following a literature review of previous studies about the
acoustic properties of some natural materials, this paper reports the acoustical characterization of the
following natural fibers: kenaf, wood, hemp, coconut, cork, cane, cardboard, and sheep wool. The absorption
coefficient and the flow resistance for samples of different thickness have been measured. By
using existing theoretical models, this study also compares the measured behavior with the theoretically
predicted behavior. This comparison shows the limits of theoretical models originally defined for porous
materials with homogeneous fibers, when they are applied to natural materials. Finally, some suggestions
for use of these natural fibers for sound absorption applications in buildings are reported.

The largest gatherings in human history prior to the advent of electronic amplification were all effectively limited by the loudness and intelligibility of the human voice. Various accounts throughout history depict single orators addressing crowds or armies of many tens of thousands, though some historians have cast doubts onto the veracity of these claims. Prior acoustic simulation has shown that reasonable intelligibility might be achieved for over 20,000 listeners for very loud orators and very quiet crowds with high density. Nearly all such accounts, however, depict a man addressing the crowd, with one notable exception: in 1588 Elizabeth I of England addressed a large army of between 5,000-23,000 troops gathered to repel the impending invasion by the Spanish Armada. The acoustic plausibility of this account is tested via STI simulations, focusing primarily on the density, noise, and environmental conditions at the time of the speech, as well as the frequency-dependent differences between female and male orators' vocal spectra and a sound radiation patterns.

Acute infection of surgical incision sites often requires specialized wound care in preparation for surgical closure. Optimal therapy for preparing such wounds for a secondary closure procedure remains uncertain. The authors report wound outcomes after administering acoustic pressure wound therapy in conjunction with negative pressure wound therapy with reticulated open-cell foam dressing changes to assist with bacteria removal from open, infected surgical-incision sites in preparation for secondary surgical closure in three patients. Before incorporating acoustic pressure wound therapy at the authors' facility, the average negative pressure wound therapy with reticulated open-cell foam dressing course prior to secondary surgical closure was 30 days; with its addition, two of three patients underwent successful surgical closure with no postoperative complications after 21 and 14 days, respectively; one patient succumbed to nonwound-related complications before wound closure. Lar...

To evaluate the feasibility and repeatability of in vivo measurement of stiffness gradients by means of acoustoelastography in the superficial digital flexor tendons (SDFTs) of clinically normal horses. 15 clinically normal horses. For each horse, stiffness gradient index and dispersion values for SDFTs in both forelimbs were evaluated in longitudinal orientation by use of acoustoelastography at 3 sites (5, 10, and 15 cm distal to the accessory carpal bone) by 2 observers; for each observer, data were acquired twice per site. The left forelimb was always scanned before the right forelimb. Lifting of the contralateral forelimb with the carpus flexed during image acquisition resulted in the required SDFT deformation in the evaluated limb. Interobserver repeatability, intraobserver repeatability, and right-to-left limb symmetry for stiffness gradient index and dispersion values were evaluated. Stiffness gradient index and dispersion values for SDFTs at different locations as well as ef...

The noise produced by complex systems such as automobiles, airplanes, machines, etc. contributes to overall noise of an environment. In the way to reduce these levels, the identification of the prominent sources is necessary. In many cases the beamforming technique is capable to carry out this task creating a visual map of the sound source. The goal of this work will be to give a basic understanding of beamforming techniques including software, hardware and to illustrate its wide applicability to common noise control and vibration problems. Resumo Os ruidos produzidos por sistemas complexos como automoveis, aeronaves, maquinas, etc. contribuem para o ruido global de um ambiente. De modo a reduzir estes niveis, a identificacao das fontes proeminentes se faz necessaria. Em muitos casos, a tecnica de beamforming e capaz de realizar esta tarefa criando um mapa visual da fonte sonora. Este trabalho objetiva fornecer o entendimento basico sobre a tecnica de beamforming, incluindo software...

Linear elastic fracture mechanics (LEFM) and the secant-intercept procedure have been used to determine that fracture toughness (KIC), critical elastic energy release rate per crack-tip extension (GIC) and plastic-zone radius for local steel, ST 60Mn product of Delta Steel Company, Aladja, Nigeria. The results show that the product is high-strength steel of low ductility.

Ultrasonic signals are often used for indoor localization, autonomous robotic navigation, and other applications where the ranges between distributed sensors need to be known. First, this paper provides a survey of the techniques described in literature to estimate the range between ultrasonic transducers. Next, a ranging technique that uses phase tracking of continuous waves is presented. This is followed by an in-depth discussion of various pulsed waveforms and their potential for ultrasonic ranging. Many of the possible sources of error in these measurements are then quantified and suggestions for error reduction are given. Finally, various examples of hardware used for ultrasonic ranging and localization are introduced.

Industrial wind turbines are frequently thought of as benign. However, the literature is reporting adverse health effects associated with the implementation of industrial-scale wind developments. This article explores the historical evidence about what was known regarding infra and low-frequency sound from wind turbines and other noise sources during the period from the 1970s through the end of the 1990s. This exploration has been accomplished through references, personal interviews and communications, and other available documentation. The application of past knowledge could improve the current siting of industrial wind turbines and avoid potential risks to health.

Purpose To determine what research evidence exists to support the use of voice measures in the clinical assessment of patients with voice disorders. Method The American Speech-Language-Hearing Association (ASHA) National Center for Evidence-Based Practice in Communication Disorders staff searched 29 databases for peer-reviewed English-language articles between January 1930 and April 2009 that included key words pertaining to objective and subjective voice measures, voice disorders, and diagnostic accuracy. The identified articles were systematically assessed by an ASHA-appointed committee employing a modification of the critical appraisal of diagnostic evidence rating system. Results One hundred articles met the search criteria. The majority of studies investigated acoustic measures (60%) and focused on how well a test method identified the presence or absence of a voice disorder (78%). Only 17 of the 100 articles were judged to contain adequate evidence for the measures studied to ...

Objective: To review current concepts of the mechanical processes of the human middle ear, and to apply them to practical issues in clinical otology and tympanoplasty surgery. Background: The wide range of conductive hearing losses associated with middle ear pathology and reconstruction cannot be adequately explained by simple models of middle ear function. Methods: Variables used to describe the system are sound pressure, volume velocity, and acoustic impedance. The relationship between specific middle ear structures and these variables is described such that inferences can be drawn regarding sound conduction in the normal, diseased, and reconstructed middle ear. Results and conclusions: Sound can be transmitted from the car canal to the cochlea via two mechanisms: the tympano-ossicular system (ossicular coupling) and direct acoustic stimulation of the oval and round windows (acoustic coupling). Acoustic coupling is negligibly small in normal ears, but can play a significant role in some diseased and reconstructed ears. In the normal ear, middle ear pressure gain (which is the result of ossicular coupling) is frequency-dependent and less than generally believed. The severity of conductive hearing loss due to middle-ear disease or after tympanoplasty surgery can be predicted by the degree to which ossicular coupling, acoustic coupling, and stapescochlear input impedance are altered. Hearing after type IV and V tympanoplasty is determined solely by acoustic coupling. The difference in magnitude between the oval- and round-window pressures is more important than the difference in phase in determining cochlear input. In tympanoplasty types I, II, and III, adequate middle-ear and round-window aeration is necessary and the tympanic membrane-ossicular configuration may be less crucial.

ABSTRACT: A model to describe the low frequency dynamic and acoustic responses of a submarine hull subject to a harmonic propeller shaft excitation is presented. The submarine is modelled as a fluid-loaded, ring stiffened cylindrical shell with internal bulkheads and end caps. The stiffeners are introduced using a smeared approach. The bulkheads are modelled as circular plates and the end closures as truncated conical shells. The propeller introduces a harmonic axial force that is transmitted to the hull through the shaft and results in ...

Knowing the geometry of a space is desirable for many applications, e.g. sound source localization, sound field reproduction or auralization. In circumstances where only acoustic signals can be obtained, estimating the geometry of a room is a challenging proposition. Existing methods have been proposed to reconstruct a room from the room impulse responses (RIRs). However, the sound source and microphones must be deployed in a feasible region of the room for it to work, which is impractical when the room is unknown. This work propose to employ a robot equipped with a sound source and four acoustic sensors, to follow a proposed path planning strategy to moves around the room to collect first image sources for room geometry estimation. The strategy can effectively drives the robot from a random initial location through the room so that the room geometry is guaranteed to be revealed. Effectiveness of the proposed approach is extensively validated in a synthetic environment, where the results obtained are highly promising.

A​ ​ study​ ​ from​ ​ UCLondon​ ​ &​ ​ UniNottingham​ ​ found​ ​ most​ ​ neurons​ ​ in​ ​ the​ ​ brain's​ ​ auditory​ ​ cortex​ ​ detect​ ​ where​ ​ a sound​ ​ is​ ​ coming​ ​ from​ ​ relative​ ​ to​ ​ the​ ​ head,​ ​ but​ ​ some​ ​ are​ ​ actually​ ​ tuned​ ​ to​ ​ a​ ​ sound​ ​ source's​ ​ actual​ ​ position in​ ​ the​ ​ world. The​ ​ PLOS-published​ ​ report​ ​ also​ ​ looked​ ​ at ​ how​ ​ head​ ​ movements​ ​ change​ ​ the​ ​ responses​ ​ of​ ​ neuro-matrices that​ ​ track​ ​ sound​ ​ location.

Article examines how our​ brain's​ ​ routine​ ​ represention of​ ​ sound​ ​ location is​ ​ in​ ​ either​ ​ an​ ​ egocentric​ ​ manner​ ​ –​ ​ for​ ​ example,​ ​ to​ ​ tell​ ​ a​ ​ phone​ ​ is​ ​ ringing to​ ​ one's​ ​ left​ ​ or​ ​ right​ ​ –​ ​ or​ ​ in​ ​ an​ ​ allocentric​ ​ manner​ ​ –​ ​ hearing​ ​ the​ ​ phone​ ​ is​ ​ on​ ​ the​ ​ table.​ ​ ​ ​ However,​ ​ as​ ​ our​ ​ head​ ​ moves neurons​ ​ with​ ​ an​ ​ egocentric​ ​ focus​ ​ expand​ ​ to​ ​ incorporate​ ​ more​ ​ neural-networks​ ​ related​ ​ to​ ​ vision​ ​ and​ ​ balance. This​ ​ expanded​ ​ engagement​ ​ offers​ ​ potential​ ​ to​ ​ improve​ ​ both​ ​ brain​ ​ plasticity​ ​ and​ ​ cognition;​ ​ when​ ​ a​ ​ dynamic influence​ ​ is​ ​ challenging​ ​ our​ ​ neurology​ ​ to​ ​ respond​ ​ differently​ ​ (the​ ​ phone's​ ​ position​ ​-​ ​ relative​ ​ to​ ​ the​ ​ ears​ ​-changes).​ ​ ​ ​ While​ ​ the​ ​ allocentric​ ​ neurons​ ​ consistently​ ​ maintain​ ​ their​ ​ response​ ​ level​ ​-​ ​ suggesting​ ​ certain sound-based​ ​ protocols​ ​ would​ ​ be​ ​ more​ ​ conducive​ ​ for​ ​ relaxation​ ​ and​ ​ meditative​ ​ practice. 

While we often hear sounds presented through earphones as being inside our heads, these findings "flesh out" more of the nature of 4th-dimensional facets of sound source algorithms.  More specifically, the acoustics can be crafted by sound designers to incorporate information about body and head movements to create a more robust externally-rendered environment.

At present, spatial sound is rapidly gaining broader recognition as our media are moving towards 3-dimensional representations using virtual reality, augmented reality or 360-video technologies. The coming-of-age of a creative discipline opening up ways of expressing and communicating with sound that were not possible before.

Sound is being represented spatially ever more accurately with evolving technologies that takes us beyond a mere reproduction of familiar acoustic reality.  At present, spatial sound is rapidly gaining broader recognition as media moves towards 3-dimensional representations using virtual reality environments/360-video technologies. What's the big deal here?

Research suggests these findings could be helpful in the design of technologies involving extended virtual reality (augmented/mixed) and enhance balance and movement process as well as neuro-rehab therapy.
Spatial sound can inform us about how we relate as human beings to our environment. It also tells us something essential about the inner workings of our perception and consciousness.

More than anything it explores the ways we experience reality through listening. Such as how the reality we hear is intrinsically based on what we know and assume about the world around us.  As we embody sound in space we’re also embodied by personal memory, can we listen from within? What then do we perceive?

One example is how spatial sound helps interpret facets of a vital link between brain waves and acoustic stimulation called frequency-following responses (FFR).  While FFR hasn't been studied in any great detail (with respect to its therapeutic and clinical utility) an interesting application looked at ​​allocentric and egocentric spatial processing under stress conditions that routinely activate sound processing FFR regions in the brain. 

Consult:

http://www.ucl.ac.uk/news/news-articles/0617/150617-egocentric-hearing

- https://www.nature.com/articles/ncomms11070  (Cortical contributions to the auditory frequency-following response revealed by MEG) Nature Communications 7, Article number: 11070 (2016) doi:10.1038/ncomms11070

- https://www.nature.com/articles/s41598-017-14910-y (Real-time Acute Stress Facilitates Allocentric Spatial Processing in a Virtual Fire Disaster) Scientific Reports 7, Article number: 14616 (2017) doi:10.1038/s41598-017-14910-y

- The Journal of CyberTherapy and Rehabilitation (JCR - ISSN  1784-9983). 

Published quarterly, the Journal of CyberTherapy and Rehabilitation (JCR), is unique among academic journals in that it focuses on the rapidly expanding worldwide trend of moving toward technological applications in healthcare.  One of the official journals of the International Association of CyberPsychology, Training, and Rehabilitation (iACToR).

For the assessment of speech privacy and security, a uniformly weighted 1/3-octave-band signal-to-noise ratio, clipped to-32 dB, has been found to be a good indicator of speech intelligibility, cadence and audibility. A parameter required in the determination of the ratio for a listener in an adjoining room to the speech source is the average sound transmission loss of the separating construction. An estimation model for the average sound transmission loss of steel stud partitions has been developed and will be discussed.

This article refers to ongoing research related to the Postdoctoral project " multichannel audio devices applied to music, sound art and bioacoustics " developed by the author for UFF (2016-2018) with support from CAPES and in collaboration with the Laboratory of Acoustics and Sound Arts – LASom/DM/IA/UNICAMP. This work aims to (1) consolidate a spatial sound projection device involving signal processing; and (2) its application in the arts (music) and science (biology and ecology) domains.

In this paper, a physics-based model for a snare drum will be discussed, along with its finite difference simulation. The interactions between a mallet and the membrane and between the snares and the membrane will be described as perfectly elastic collisions. A novel numerical scheme for the implementation of collisions will be presented, which allows a complete energy analysis for the whole system. Viscothermal losses will be added to the equation for the 3D wave propagation. Results from simulations and sound examples will be presented.

"Thermo-acoustic investigations of the non linear properties of fructose in aqueous solution of NaCl and MgCl2 have been
done in the temperature range, 298.15K - 308.15K at various concentrations using volume expansivity data. Several nonlinear parameters such as Moelwyn-Hughes parameter (C1), Bayer’s non-linear parameter (B/A), reduced volume( ), reduced isothermal bulk modulus (â),Sharma’s constants (S0, S*, S*0), Huggins parameter (F), isobaric acoustical parameter (K), isochoric acoustical parameter (K”), isothermal acoustical parameter(K’), fractional free volume(f), repulsive exponent (ç), reduced volume expansivity (a*), internal pressure (Pi), cohesive energy density (âi), critical temperature (T*) and thermo-acoustical parameter such as A* and B* have been studied. The non-linearity behavior of these parameters has been explained in terms of the concentration and thermal changes in the systems under investigation. The present analysis provides a deep insight about the nature and types of interactions prevalent in the solutions of electrolytes and fructose. The obtained results provide a reliable basis to understand the action of electrolytes and bio-molecules in the bio-chemical processes undergoing in a bio-physical system."

Many pre-state societies around the world give special importance to places where distinctive acoustic effects are generated. These places often receive special treatment including the production of rock paintings in them. In the Western Mediterranean, it seems that outstanding acoustic effects such as directional echoes, augmented audibility and long reverberation time are present in some rock art areas with Neolithic depictions made between the 7 and 4 millennia BC. These have been painted in different styles that have been given the name of Macroschematic, Levantine and Schematic rock art styles. On the basis of the results of our acoustic tests, we argue that there is a strong probability of acoustics having been used as a method by Neolithic artists to select the shelters in which to produce rock art. This paper presents the results of the ongoing ARTSOUNDSCAPES ERC Project on archaeoacoustics. This project seeks to explore the role of sound in the creation and use of rock art ...