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Wednesday, May 6, 2020 | History

3 edition of Sound absorption at the soil surface. found in the catalog.

Sound absorption at the soil surface.

Anthony R. P. Janse

Sound absorption at the soil surface.

by Anthony R. P. Janse

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  • 1 Currently reading

Published by Centre for Agricultural Publishing and Documentation in Wageningen .
Written in English

    Subjects:
  • Soil structure -- Measurement.,
  • Absorption of sound.

  • Edition Notes

    Statement[By] A. R. P. Janse.
    SeriesAgricultural Research Reports, 715
    Classifications
    LC ClassificationsS239 .A37 no. 715
    The Physical Object
    Paginationviii, 215 p.
    Number of Pages215
    ID Numbers
    Open LibraryOL4055328M
    LC Control Number79431409

    Sound Energy absorbed by infinite surface in diffuse sound field αST = Equation 4 This is an idealized quantity which cannot be measured directly. Normal Incidence Coefficient αN The normal incidence absorption coefficient is the ratio of energy absorbed/energy incident, for a plane wave, normally incident on an absorptive surface. It is File Size: KB. At frequencies below 1 kHz, sound absorption coefficients in the ocean are a function of pH, and at higher frequencies they are dependent upon MgSO pH dependent terms are attributable to relaxation of B(OH) 3 and MgCO 3 species, and the ensemble effect has been approximated (Mellen et al., a) as α = α 1 (MgSO 4) + α 2 (B(OH) 3) + α 3 (MgCO 3), where α is the absorption Cited by:

    Feasibility study of estimating the porosity of soils from sound absorption measurements Article (PDF Available) in Measurement 77() September . Acoustic panels are generally specified by the sound absorption coefficient. What this specification tells us is that if the absorption at a given frequency shows a value of , the panel will be % effective at absorbing sound at that specific frequency. A value of would indicate 50% absorption.

    The results for different soil depths (50, , , mm) showed that even the thin soil layer with a depth of 50 mm provided a significant absorption coefficient of about at around Hz. Sound absorption, measured in a plane-wave impedance tube, for glass fiber, Alporas foam in the as-received condition, and Alporas foam after 10% compression to rupture the cell faces. σ rises to about at Hz. Compressing the foam by 10% bursts many of the cell faces, and increases absorption, as shown in the bottom figure.


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Sound absorption at the soil surface by Anthony R. P. Janse Download PDF EPUB FB2

Sound absorption at the soil surface (Agricultural Research Reports, ) [Janse, Anthony R. P] on *FREE* shipping on qualifying offers. Sound absorption at the soil surface (Agricultural Research Reports, )Author: Anthony R.

P Janse. Sound absorption at the soil surface. [Anthony R P Janse] -- The properties of a soil structure may be examined in various manners. As well as a study of the stability, a knowledge of the geometry of the volume of air filled pores is often needed.

Next the principles of the propagation of sound in porous materials are presented. For a sample of thickness l and having a rigid backing, the specific acoustic impedance Z at the free surface is given by Z = W m coth(γ m l), where γ m is the propagation constant for acoustical waves in the sample and W m Cited by: 2.

situated at x = 0 (x thus takes on negative values inside the tube). The sound field in the tube may be considered as the superposition of two waves, the incident wave, travelling from the loudspeaker towards the sample and im­.

pinging on the sample surface at normal incidence (p. in figure la) and the re­. including absorption of sound in air, non-uniformity of the propagation medium due to meteorological conditions (refraction and turbulence), and interaction with an absorbing ground and solid obstacles (such as barriers).File Size: KB.

The effect of each type of coverage in the erosion plots was evaluated by means of the apparent sound absorption coefficient of the surface (α).

(with K = 1 – adopted) and Eq. were used for the calculation. It is noteworthy that the depth of penetration of the incident wave into the ground was not measured. Statistical analysisCited by: 2. The sound absorbing effectiveness of sound absorbing material for plane wave angle of incidence at angles other than normal incidence is different for locally reacting and bulk-reacting (or extended reacting liners).

Locally reacting liners: Particle velocity confined to the direction normal to the surface. The results of measurements of sound absorption by the body surface of man and fur‐bearing animals are reported for the frequency range to 12, c.p.s.

The acoustical impedances and the absorption coefficients of the surfaces were determined from the resonance characteristics of an air‐filled tube.

The end of the tube was closed first by a rigid wall and then by the unknown by: 6. Porous sound absorption material is most widely used as sound absorption functional material, which is made of glass fiber, wool fiber, wood fiber, or polyester fiber and adhesive as board or sound proof felt.

There are many macropores and micropores that are interconnected and opened to the surface inside the material. The most relevant visual predictor for the sound absorption of bark is its roughness.

Interestingly, moss grown barks provide a strong increase in absorption in the frequency range up to Hz. Especially in dense tree belts, bark absorption might have an influence on the final noise shielding performance.

speed of sound in the soil samples as a function of four levels of acterize living tissues. Seismic waves of frequency below Seismic waves of frequency below soil moisture and two levels of compaction. ABSORPTION COEFFICIENTS FREQUENCY Hz MATERIAL THICKNESS MASONRY WALLS Rough concrete 0,02 0,03 0,03 0,03 0,04 0,07 Smooth unpainted concrete 0,01 0,01 0,02 0,02 0,02 0,05 Smooth concrete, painted or glazed 0,01 0,01 0,01 0,02 0,02 0,02 Porous concrete blocks (no surface finish) 0,05 0,05 0,05 0,08 0,14 0,2File Size: KB.

where, ΔA is the additional sound absorbed capacity of sound absorption material, S 2 is the surface area of the tested sample, and α 2 is the sound absorption coefficient of the. speed of sound is m/sec, yielding a ρc value of Pas/m.

Using these values in Equation (4) yields a value for r i I I ofwhich means that percent of the energy is reflected from the silica surface; only percent is transmitted. Lower density materials will reflect less energy, as will materials with lower sound File Size: KB.

Survey Staff. Field book for describing and sampling soils, Version Natural Resources Conservation Service, National Soil Survey Center, Lincoln, NE. Cover Photo: A polygenetic Calcidic Argiustoll with an A, Bt, Bk, 2BC, 2C horizon sequence.

This soil formed in Peoria Loess thatMissing: Sound absorption. The acoustic properties of recycled polyurethane foams are well known.

Such foams are used as a part of acoustic solutions in different fields such as building or transport. This paper aims to seek improvements in the sound absorption of these recycled foams when they are combined with fabrics.

For this aim, foams have been drilled with cylindrical perforations, and also combined with Author: Roberto Atiénzar-Navarro, Romina del Rey, Jesús Alba, Víctor J.

Sánchez-Morcillo, Rubén Picó. Using discarded feather fibers (DFs) and ethylene vinyl acetate (EVA) copolymer, the DFs/EVA composites with good sound absorption performance were prepared by hot-pressing method. The effects of hot-pressing temperature, mass fraction of DFs, density and thickness of composites on the sound absorption properties were studied by the controlling variable : Lihua Lyu, Yingjie Liu, Jihong Bi, Jing Guo.

Natural fiber and wood are environmentally friendly materials with multiscale microstructures. The sound absorption performance of flax fiber and its reinforced composite, as well as balsa wood, were evaluated using the two-microphone transfer function technique with an impedance tube system.

The microstructures of natural materials were studied through scanning electrical microscope in order Cited by: this finding. For every measurement mode, a fixed sound was released by surface impedance meter toward the road surface in calibration mode till 6 second.

After completion of calibration mode, the instrument is put in actual measurement mode and the sound is released till 6 second for absorption and reflection of road Size: KB.

When soil conditions are restrictive due to high groundwater, flooding, slowly permeable soil, shallow bedrock, or inadequate lot size, advanced treatment as discussed in Chapter VI, and/or alternative soil absorption systems are often used.

They provide fundamentally sound. This work applied acoustic technique to relate the response of a signal sound to different surfaces, measured in equivalent sound pressure level, with the factors governing soil erosion plots in reduced scale ( x m) were built on.Sound absorbing materials are used in buildings to dissipate sound energy into heat using viscous and thermal processes.

Sound absorbers increase the transmission loss of walls, decrease the reverberation time of rooms, and attenuate the noise generated by internal sound sources.

Porous absorbers (fibrous, cellular, or granular) are the most used materials in noise control applications because.sound-absorbing structures that can attain near-equality for the causal relation with very high absorption performance; such structures aredenoted “optimal.” Our strategy involves using carefully designed acoustic metamaterials as backing to a thin layer of conventional sound absorbing material, e.g., acoustic sponge.