Design of a jagged-edge noise barrier: Numerical and experimental study

Abstract

The present work is a continuation of the investigation of a novel design for a noise barrier with a jagged top edge instead of the conventional straight top edge. Previous work showed that making the top edge of the barrier jagged can in some, but not all, cases reduce the strength of the diffracted sound field behind the barrier, although the barrier's performance depended on receiver location. The present work describes a profile for a jagged-edge barrier that substantially reduced (by almost 70%) the peak of the diffracted sound-pressure signal behind the barrier compared with the peak sound pressure at the same location behind a straight-edge barrier of the same average height. The noise reduction provided by an optimized design for the jagged-edge barrier did not depend on receiver location. The optimum geometry for the jagged-edge profile was determined from extensive numerical investigations of different design parameters using an analytical model termed the Directive Line Source Model. Subsequently, the performance of the jagged-edge profile was tested in the laboratory using a spark source in air. Good agreement between experimental data and numerical predictions supported the validity of the analytical model. © 2004 Institute of Noise Control Engineering

Finding optimal geometries for noise barrier tops using scaled experiments

“…Only in the experiments with large microphone-source angles does the RN top show any modest increase in the single number insertion loss rating N compare to a thin vertical screen. This result does not agree well with previously reported results that such jagged tops are significantly more effective than thin vertical screens 12,15,34 . These authors, however, did not consider the spectrum variability laterally along the barrier.…”

“…In our approach, to smooth these variations, the along barrier averaging for the insertion loss spectra was used. Note also, that the results reported by Menounou and You 12,15 for jagged tops show only the decrease of the sound pressure peak amplitude level, compare to the S top, and its significant variation in the along barrier direction, but no data is supplied on insertion losses. The lack of sound level calculations in the above-mentioned studies has also been noted previously by Pigasse and Kragh 35 .…”

Solving Noise Pollution Issue Using Plenum Window with Perforated Thin Box

“…Therefore, a perforated thin box using the concept of Helmholtz resonance is installed on a plenum window in the present study in order to enhance the performance of the plenum window at 1000 Hz. In addition, some other previous studies also claimed that noise barrier with jagged edge had greater noise attenuation ability than straight edge [14][15][16][17]. Therefore, in the present study, since sound diffraction might be occurred over the gap or edge of the plenum window's glass pane, jagged flaps with different angles were installed on the edge of the glass pane in order to reduce the energy of the diffracted sound.…”

Use of Noise Barriers for Helicopter Noise Mitigation

“…For modeling the diffraction from the top edge of the barrier, the DLSM (Directive Line Source Model) [1][2][3] has been employed. According to DLSM, the problem of diffraction is transformed into a radiation problem from directive point sources continuously distributed along the edge of the barrier.…”

“…Finally, it should be noted that for the area studied, the 20m long barrier has the same effect as the infinitely long barrier. 3.5 Use of jagged instead of straight edge barriers Previous work on jagged top edge barriers [3] has shown their improved shielding performance compared to straight edge barriers of the same average height. A simple jagged edge profile was numerically investigated for a single receiver location behind the barrier and an omni-directional noise source having spectrum similar to the helicopter noise spectrum.…”