From a profiled diffuser to an optimized absorber

Wu, Tao; Cox, Trevor J.; Lam, Y. W.

doi:10.1121/1.429596

Cited by 61 publications

(43 citation statements)

References 3 publications

(1 reference statement)

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“…It should be reminded that viscous and thermal loses were ignored in the calculation of the QRD admittance. For very small well widths, these effects could be significant and introduce larger impedance as well as significant absorption [11,12].…”

Section: Barrier Configurations With Different Qrd Designsmentioning

confidence: 99%

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Performance of profiled single noise barriers covered with quadratic residue diffusers

Monazzam

Lam

2005

Applied Acoustics

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Section: Barrier Configurations With Different Qrd Designsmentioning

confidence: 99%

“…It should also be noted that the QRDs used in the investigation are nonabsorptive. It will be an interesting further work to investigate if an absorptive QRD, as suggested in References [11,12], can further improve the performance of a QRD barrier.…”

Section: F Broad Band Insertion Lossmentioning

confidence: 99%

Performance of profiled single noise barriers covered with quadratic residue diffusers

Monazzam

Lam

2005

Applied Acoustics

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“…Fujiwara (Fujiwara, Furuta, 1991) installed an absorber on the barrier edge and stated that because the absorber reduces the sound pressure on the edge, the barrier efficiency has been improved. Another study (Wu et al, 2000) has also shown that the variable depth sequence concept can be used to improve significantly the absorption and impedance characteristics of conventional constant depth design.…”

Section: Absorption By Qrd and Prdmentioning

confidence: 99%

Performance of Environmental T-shape Noise Barriers Covered with Primitive Root Diffusers

Monazzam¹,

Naderzadeh²,

Nassiri³

et al. 2010

Archives of Acoustics

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There is a considerable increase in the use of noise barriers in recent years. Noise barriers as a control noise solution can increase the insertion loss to protect receivers. This paper presents the results of an investigation about the acoustic efficiency of primitive root sequence diffuser (PRD) on an environmental single T-shape barrier design. A 2D boundary element method (BEM) is used to predict the insertion loss of the tested barriers. The results of rigid and with a different sequence diffuser coverage are also predicted for comparison. Employing PRD on the top surface of T-shape barrier has been found to improve the performance of barriers in comparison with the use of rigid and QRD coverage at the examined receiver locations. It has been found that decreasing the design frequency of PRD shifts the frequency effects towards lower frequencies, and therefore the overall A-weighted insertion loss is improved. It was also found that using wire mesh with reasonably efficient resistivity on the top surface of PRD improves the efficiency of the reactive barriers; however utilizing wire meshes with flow resistivity higher than the specific acoustic impedance of air on the PRD top of a diffuser barrier significantly reduces the performance of the barrier within the frequency bandwidth of the diffuser. The performance of a PRD covered T-shape barrier at 200 Hz was found to be higher than that of its equivalent QRD barriers in both the far field and in areas close to the ground. The amount of improvement compared made by PRD barrier compared with its equivalent rigid barrier at far field is about 2 to 3 dB, while this improvement relative to the barrier model "QR4" can reach up to 4-6 dB.

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“…According to Wu's assumption (Wu, 2000), textile cover is purely resistive, so the reactance part of z is x = 0. For the textile cover used in the measurements, m = 0.15 kg/m 2 .…”

Section: Absorption Of a Resistive Layer Above A Rigid Platementioning

confidence: 99%

“…He was also the first to calculate and measure the influence of resistive layers situated on the entrances of the wells on the absorption coefficient. Based on his approach, Wu et al (2000) pointed out the possibility of creating a highly absorptive structure that would combine the QRD and a resistive covering.…”

Section: Introductionmentioning

confidence: 99%

Multimodal Ultrasonic Imaging for Breast Cancer Detection

Camacho

Medina

Cruza

et al. 2012

Archives of Acoustics

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Ultrasound is used for breast cancer detection as a technique complementary to mammography, the standard screening method. Current practice is based on reflectivity images obtained with conventional instruments by an operator who positions the ultrasonic transducer by hand over the patient's body. It is a non-ionizing radiation, pain-free and not expensive technique that provides a higher contrast than mammography to discriminate among fluid-filled cysts and solid masses, especially for dense breast tissue. However, results are quite dependent on the operator's skills, images are difficult to reproduce, and state-of-the-art instruments have a limited resolution and contrast to show micro-calcifications and to discriminate between lesions and the surrounding tissue. In spite of their advantages, these factors have precluded the use of ultrasound for screening.This work approaches the ultrasound-based early detection of breast cancer with a different concept. A ring array with many elements to cover 360• around a hanging breast allows obtaining repeatable and operator-independent coronal slice images. Such an arrangement is well suited for multi-modal imaging that includes reflectivity, compounded, tomography, and phase coherence images for increased specificity in breast cancer detection. Preliminary work carried out with a mechanical emulation of the ring array and a standard breast phantom shows a high resolution and contrast, with an artifact-free capability provided by phase coherence processing.

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From a profiled diffuser to an optimized absorber

Cited by 61 publications

References 3 publications

Performance of profiled single noise barriers covered with quadratic residue diffusers

Performance of profiled single noise barriers covered with quadratic residue diffusers

Performance of Environmental T-shape Noise Barriers Covered with Primitive Root Diffusers

Multimodal Ultrasonic Imaging for Breast Cancer Detection

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