Tutorial on sound propagation outdoors

Embleton, T. F. W.

doi:10.1121/1.415879

Cited by 260 publications

(166 citation statements)

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“…This simplified model can be enhanced by considering the case of an infinitely long and straight road where continuous traffic approximately behaves as a line source in such a manner that, at enough distance from the individual sources, sound levels fall 3 dB per doubling of distance as cylindrical wavefront does [14]. In other words, an attenuation proportional to 1/r (being r the traveled distance) is finally obtained due to geometrical spreading.…”

Section: Multiple Reflections Modelmentioning

confidence: 99%

Optimum control of broadband noise by arrays of cylindrical units made of a recycled material

́a-Chocano

Sánchez‐Dehesa

2013

Applied Acoustics

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ElsevierGarcia Chocano, VM.; Sánchez-Dehesa Moreno-Cid, J. (2013) AbstractWe report acoustic barriers that are designed to attenuate efficiently broadband noise. The barriers are structures consisting of only three layers of cylindrical units containing rubber crumb, a sound absorbing material obtained from recycling used tires. An optimization algorithm is developed to obtain the material distribution and dimensions of the building units giving the best attenuation properties for traffic noise, which is here chosen as an example in which the design procedure is applied. A good agreement is found between predictions and measurements for a 3 meters height barrier that has been characterized in a transmission room.

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Section: Multiple Reflections Modelmentioning

confidence: 99%

Optimum control of broadband noise by arrays of cylindrical units made of a recycled material

́a-Chocano

Sánchez‐Dehesa

2013

Applied Acoustics

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“…[61] The most significant time-dependent factors influencing sound propagation outdoors are (1) refraction from vertical gradients in temperature and wind, (2) classical and molecular absorption (dependent on temperature, ambient pressure, and relative humidity), (3) effects of the ground impedance (affected by snow cover and vegetation), and (4) scattering from turbulence [Reynolds, 1873; Piercy et al, 1977; Larsson and Israelsson, 1991;Embleton, 1996;Ostashev, 1997]. Fortunately, infrasonic propagation for the frequencies and range (13.4 km) we consider in this study is much simpler: absorption is negligible [Sutherland and Bass, 2004], the surface impedance is very large such that very little energy is lost to the ground surface [Bass, 1991], and turbulence is typically disregarded.…”

Section: Atmospheric Propagation Effects and Signal Intermittencymentioning

confidence: 99%

The source of infrasound associated with long‐period events at Mount St. Helens

Matoza¹,

Garcés²,

Chouet³

et al. 2009

J. Geophys. Res.

101

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[1] During the early stages of the [2004][2005][2006][2007][2008] Mount St. Helens eruption, the source process that produced a sustained sequence of repetitive long-period (LP) seismic events also produced impulsive broadband infrasonic signals in the atmosphere. To assess whether the signals could be generated simply by seismic-acoustic coupling from the shallow LP events, we perform finite difference simulation of the seismo-acoustic wavefield using a single numerical scheme for the elastic ground and atmosphere. The effects of topography, velocity structure, wind, and source configuration are considered. The simulations show that a shallow source buried in a homogeneous elastic solid produces a complex wave train in the atmosphere consisting of P/SV and Rayleigh wave energy converted locally along the propagation path, and acoustic energy originating from the source epicenter. Although the horizontal acoustic velocity of the latter is consistent with our data, the modeled amplitude ratios of pressure to vertical seismic velocity are too low in comparison with observations, and the characteristic differences in seismic and acoustic waveforms and spectra cannot be reproduced from a common point source. The observations therefore require a more complex source process in which the infrasonic signals are a record of only the broadband pressure excitation mechanism of the seismic LP events. The observations and numerical results can be explained by a model involving the repeated rapid pressure loss from a hydrothermal crack by venting into a shallow layer of loosely consolidated, highly permeable material. Heating by magmatic activity causes pressure to rise, periodically reaching the pressure threshold for rupture of the ''valve'' sealing the crack. Sudden opening of the valve generates the broadband infrasonic signal and simultaneously triggers the collapse of the crack, initiating resonance of the remaining fluid. Subtle waveform and amplitude variability of the infrasonic signals as recorded at an array 13.4 km to the NW of the volcano are attributed primarily to atmospheric boundary layer propagation effects, superimposed upon amplitude changes at the source.Citation: Matoza, R.

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“…MARTEN et al (1977) argued that heights between 1 m above ground up to 1 m below the canopy are the best for sound transmission in tropical forests, because both transmission through the canopy or near the ground increased signal attenuation. Above the canopy, sound can degrade rapidly by wind turbulence and refraction when temperature above the canopy is higher than the temperature underneath of it (EMBLETON 1996, BRADBURY & VEHRENCAMP 1998. In temperate forests, the position of the caller relative to the dense canopy has been demonstrated to be more important than the height itself (MATHEVON et al 1996, BLUMENRATH & DABELSTEEN 2004.…”

Section: Discussionmentioning

confidence: 99%

Does the golden lion tamarin, Leontopithecus rosalia (Primates: Callitrichidae), select a location whithin the forest strata for long distance communication?

Sabatini

Ruiz‐Miranda

2010

Zoologia (Curitiba, Impr.)

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The effectiveness of auditory signals for long distance communication depends on environmental, biological and behavioral factors. Because the environment is not homogenous, it is expected that vocalizing animals would emit signals from locations (perches) that would facilitate call propagation and perception. Perching behavior has been widely documented in birds, but not in primates. The aim of this study was to ascertain whether golden lion tamarins - Leontopithecus rosalia (Linnaeus, 1766) - emit long calls from places (perch) within the forest strata that are higher above the ground with respect to places used for baseline behaviors. We compared the forest stratum (upper, middle and lower strata) and habitat type (hill, swamp and lowland forests) used for long calls with those used for other behaviors. The focal animal technique (n = 4) of 10 minutes with instantaneous sampling at two minutes were used if the subjects were not emitting long calls, and the all-occurrences technique if a focal individual emitted a two-phrase long call. Golden lion tamarins used all strata in all habitat types, including the ground, when they were not emitting long calls, but vocalized long calls most often from the upper strata, just underneath the canopy, in the three habitats studied. From a total of 29 bouts of long calls, 21 were initiated by individuals that were in the lower stratum; however, these individuals subsequently migrated to the upper stratum, while still vocalizing. Calling from the upper strata of the forest, just underneath canopy could improve sound transmission, perception, visual contact or a combination of these types of communication. Based on these considerations, we hypothetize that by placing themselves in the upper strata of the forest when emitting calls, golden lion tamarins enhance their likelhood to locate other callers, not only be improving sound reception, but also by increasing their chances to make visual contact with them

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Tutorial on sound propagation outdoors

Cited by 260 publications

References 0 publications

Optimum control of broadband noise by arrays of cylindrical units made of a recycled material

Optimum control of broadband noise by arrays of cylindrical units made of a recycled material

The source of infrasound associated with long‐period events at Mount St. Helens

Does the golden lion tamarin, Leontopithecus rosalia (Primates: Callitrichidae), select a location whithin the forest strata for long distance communication?

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