Improved Method for Selecting Scale Factors and Model Materials for Scale Modelling of Outdoor Sound Propagation

Busch, Todd; Hodgson, Murray

doi:10.1006/jsvi.2000.3462

Cited by 6 publications

(3 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…At 1:31.5 scale, felt was found to have an effective flow resistivity of 50 to 80 kN•s•m Ϫ4 , 19 and was a good model of a forest floor. 21 Figure 8 shows, for wedge-shaped berms of 1:3 slope, that changes of surface impedance caused the largest variation of IL.…”

Section: Alternative Surface Impedancementioning

confidence: 98%

“…Three model materials were selected 19 to simulate packed-earth berms and ground ͑effective flow resistivities of 4000 to 8000 kN•s•m Ϫ4 ͒, 21 vertical walls or roadways ͑20 000 kN•s•m Ϫ4 ͒, and an atypically soft surface such as a forest floor ͑20 to 80 kN•s•m Ϫ4 ͒. Roadways were simulated using varnished particleboard, walls using dense polystyrene, and packed-earth berms and ground using expanded polystyrene.…”

Section: B Scale-model Materialsmentioning

confidence: 99%

See 1 more Smart Citation

Scale-model study of the effectiveness of highway noise barriers

Busch

Hodgson

Wakefield³

2003

The Journal of the Acoustical Society of America

View full text Add to dashboard Cite

A scale-model facility was developed to test the insertion loss (IL) of highway noise barriers. Three model materials were utilized to simulate packed-earth berms and ground (expanded polystyrene), vertical walls (dense polystyrene), and roadways (varnished particleboard). Thirty-eight noise-barrier configurations were tested and used to compare how IL varied with changes to the barrier profile for walls, berms, and combinations of walls and berms for receivers at a representative, highway-adjacent location. The atmospheric conditions were assumed to be homogeneous and nonrefracting. Changes of barrier surface impedance were also assessed. A highway line source was simulated by positioning both an air-jet point source and a receiver microphone at a series of equally spaced points, in order to form an array of source-receiver measurement pairs making differing angles of propagation to the noise-barrier crest line. The IL measurement results are presented in unweighted third-octave bands. In addition, total A-weighted insertion losses (ILA) were obtained by applying an A-weighted, traffic-noise spectrum. When a berm was modeled with surface impedance closely matching that of packed earth, it was found that walls outperformed berms by 1 to 2 dBA. When the surface impedance of a berm was modeled to be acoustically soft, the ILA increased sufficiently to favor berms by about 2 dBA. The result for an acoustically soft berm does not support the long-standing practice of assuming that earth berms outperform walls by 3 dBA, but is consistent with the performance predicted by newer prediction algorithms. When the slopes of berms were made shallower, the IL generally decreased for a berm alone, but generally increased in cases with a wall atop the berm.

show abstract

Section: Alternative Surface Impedancementioning

confidence: 98%

Section: B Scale-model Materialsmentioning

confidence: 99%

Scale-model study of the effectiveness of highway noise barriers

Busch

Hodgson

Wakefield³

2003

The Journal of the Acoustical Society of America

View full text Add to dashboard Cite

show abstract

“…Although Busch et al 26 have reported an improved technique for simultaneously selecting both an optimal scale factor and optimal model materials, no attempt is made in our laboratory measurements to select the most appropriate materials to model an outdoor porous ground surface. However, the use of carpet-covered ground will allow a validation of the coherent and incoherent models by comparing theoretical predictions with precise indoor measurements.…”

Section: B Indoor Laboratory Measurementsmentioning

confidence: 96%

The propagation of sound in narrow street canyons

2002

The Journal of the Acoustical Society of America

View full text Add to dashboard Cite

This paper addresses an important problem of predicting sound propagation in narrow street canyons with width less than 10 m, which are commonly found in a built-up urban district. Major noise sources are, for example, air conditioners installed on building facades and powered mechanical equipment for repair and construction work. Interference effects due to multiple reflections from building facades and ground surfaces are important contributions in these complex environments. Although the studies of sound transmission in urban areas can be traced back to as early as the 1960s, the resulting mathematical and numerical models are still unable to predict sound fields accurately in city streets. This is understandable because sound propagation in city streets involves many intriguing phenomena such as reflections and scattering at the building facades, diffusion effects due to recessions and protrusions of building surfaces, geometric spreading, and atmospheric absorption. This paper describes the development of a numerical model for the prediction of sound fields in city streets. To simplify the problem, a typical city street is represented by two parallel reflecting walls and a flat impedance ground. The numerical model is based on a simple ray theory that takes account of multiple reflections from the building facades. The sound fields due to the point source and its images are summed coherently such that mutual interference effects between contributing rays can be included in the analysis. Indoor experiments are conducted in an anechoic chamber. Experimental data are compared with theoretical predictions to establish the validity and usefulness of this simple model. Outdoor experimental measurements have also been conducted to further validate the model.

show abstract