Outdoor ground impedance models

Many models for the acoustical properties of rigid-porous media require knowledge of parameter values that are not available for outdoor ground surfaces. The relationship used between tortuosity and porosity for stacked spheres results in five characteristic impedance models that require not more th...

Full description

Saved in:
Bibliographic Details
Published in:The Journal of the Acoustical Society of America 2011-05, Vol.129 (5), p.2806-2819
Main Authors: Attenborough, Keith, Bashir, Imran, Taherzadeh, Shahram
Format: Article
Language:English
Subjects:
Acoustics
Aeroacoustics, atmospheric sound
Construction Materials
Environment
Exact sciences and technology
Fittings
Fundamental areas of phenomenology (including applications)
Grasslands
Grounds
Hydrocarbons
Impedance
Mathematical models
Mathematics
Models, Theoretical
Noise
Noise, Occupational - statistics & numerical data
Noise, Transportation - statistics & numerical data
Outdoor
Physics
Poaceae
Porosity
Soil
Trees
Wood
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:Many models for the acoustical properties of rigid-porous media require knowledge of parameter values that are not available for outdoor ground surfaces. The relationship used between tortuosity and porosity for stacked spheres results in five characteristic impedance models that require not more than two adjustable parameters. These models and hard-backed-layer versions are considered further through numerical fitting of 42 short range level difference spectra measured over various ground surfaces. For all but eight sites, slit-pore, phenomenological and variable porosity models yield lower fitting errors than those given by the widely used one-parameter semi-empirical model. Data for 12 of 26 grassland sites and for three beech wood sites are fitted better by hard-backed-layer models. Parameter values obtained by fitting slit-pore and phenomenological models to data for relatively low flow resistivity grounds, such as forest floors, porous asphalt, and gravel, are consistent with values that have been obtained non-acoustically. Three impedance models yield reasonable fits to a narrow band excess attenuation spectrum measured at short range over railway ballast but, if extended reaction is taken into account, the hard-backed-layer version of the slit-pore model gives the most reasonable parameter values.
ISSN:0001-4966
1520-8524
DOI:10.1121/1.3569740