Experimental measurement of the acoustic sensitivity kernel

Roux, Philippe; Marandet, Christian; Nicolas, Barbara; Kuperman, W. A.

doi:10.1121/1.4808111

Cited by 11 publications

(3 citation statements)

References 9 publications

(16 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Over the last 20 years, SK physics was developed first in geophysics (Woodward, 1988;Marquering et al, 1988;Dahlen and Baig, 2002;Dahlen, 2004) and then more recently in acoustics (Skrasoulis and Cornuelle, 2004), as a perturbation approach that linearly relates a change in the wavefield between a source and a receiver to a local perturbation in the medium properties. On the assumption that the wavefield perturbation satisfies the first-order Born approximation, the SK was experimentally demonstrated to be a solution of the forward scattering problem for changes at the surface or in the volume (Sarkar et al, 2012;Roux et al, 2013b). The SK has also been used to perform inversions, such as for travel-time tomography and target localization (Marandet et al, 2011) in a multipath waveguide configuration, with the experimental data recorded at the ultrasonic scale.…”

Section: Introductionmentioning

confidence: 99%

Inverting for a deterministic surface gravity wave using the sensitivity-kernel approach

Roux

Nicolas

2014

The Journal of the Acoustical Society of America

Self Cite

View full text Add to dashboard Cite

The dynamic imaging of a deterministic gravity wave propagating at an air-water interface requires continuous sampling of every point at this interface. This sampling can be done acoustically using waves that propagate in the water column but have specular reflection points that fully scan the air-water interface. This study aims to perform this complex task experimentally, with identical ultrasonic source and receiver arrays that face each other in a 1-m-long, 5-cm-deep fluid waveguide, and with frequencies in the MHz range. The waveguide transfer matrix is recorded 100 times per second between the source-receiver arrays, while a gravity wave is generated at the air-water interface. Through the beamforming process, a large set of acoustic multi-reverberated beams are isolated and identified that interact with the air-water interface. The travel-time and amplitude modulations of each eigenbeam are measured when the surface gravity wave travels through the source-receiver plane. Linear inversion of the travel-time and amplitude perturbations is performed from a few thousand eigenbeams using diffraction-based sensitivity kernels. Inversion results using travel-times, amplitudes, or these two observables together, lead to accurate spatial-temporal patterns of the surface deformation. The advantages and limitations of the method are discussed.

show abstract

Section: Introductionmentioning

confidence: 99%

Inverting for a deterministic surface gravity wave using the sensitivity-kernel approach

Roux

Nicolas

2014

The Journal of the Acoustical Society of America

Self Cite

View full text Add to dashboard Cite

show abstract

“…The intrapartum and immediate postnatal periods [1] are a time of significant risk to both mother and her child [2]. Adverse intrapartum events are implicated in 23% of neonatal deaths, 32% of stillbirths and 42% of maternal deaths as well as a poorly measured burden of long-term impairment and disability worldwide [3].…”

Section: Introductionmentioning

confidence: 99%

Quality of intrapartum care at Mulago national referral hospital, Uganda: clients’ perspective

Kigenyi

Tefera

Nabiwemba

et al. 2013

BMC Pregnancy Childbirth

View full text Add to dashboard Cite

BackgroundQuality of intrapartum care is an important intervention towards increasing clients’ utilization of skilled attendance at birth and accelerating improvements in newborn’s and maternal survival and wellbeing. Ensuring quality of care is one of the key challenges facing maternal and neonatal services in Uganda. The study assessed quality of intrapartum care services in the general labor ward of the Mulago national referral and teaching hospital in Uganda from clients’ perspective.MethodsA cross sectional study was conducted using face to face interviews at discharge with 384 systematically selected clients, who delivered in general labor ward at Mulago hospital during May, 2012. Data analysis was done using STATA Version (10) software. Means and median general index scores for quality of intrapartum care services were calculated. Linear regression models were used to determine factors associated with quality of care.ResultsOverall, quality of intrapartum care mean index score was 49.4 (standard deviation (sd) 15.46, and the median (interquartile range (IQR)) was 49.1 (37.5–58.9). Median index scores (IQR) per selected quality of care indicators were; dignity and respect 75 (50–87.5); relief of pain and suffering 71.4 (42.8-85.7); information 42.1 (31.6-55.3); privacy and confidentiality 33.3 (1–66.7); and involvement in decision making 16.7 (1–33.3). On average, higher educational level (college/university) (β: 6.81, 95% CI: 0.85-15.46) and rural residence of clients (β: 5.67, 95% CI: 0.95-10.3) were statistically associated with higher quality scores.ConclusionThis study has revealed that quality of intrapartum care services from clients’ perspective was low. Improvements should be focused on involving clients in decision making, provision of information about their conditions and care, and provision of privacy and confidentiality. There is also need to improve the number and availability of health care providers in the labor ward.

show abstract

“…19 In the present study, the SK between a set of sources and receivers is measured experimentally, which determines the perturbation in the acoustic field as a function of a local perturbation at a target position that is associated with the direct arrivals. 20 The target used in this experiment is an aggregate of ping-pong balls, and the SK is obtained by the measurement of the difference in the scattered field without and with the aggregate inside the cavity, with the positions of the sources and receivers fixed, and at the periphery of the tank. The SK derived from the difference between the two fields is used to localize the target at any position within the measurement region.…”

Section: Introductionmentioning

confidence: 99%

Target localization through a data-based sensitivity kernel: A perturbation approach applied to a multistatic configuration

Yıldız¹,

Roux²,

Rakotonarivo³

et al. 2014

The Journal of the Acoustical Society of America

Self Cite

View full text Add to dashboard Cite

A method to isolate the forward scattered field from the incident field on an object in a complex environment is developed for the purpose of localization. The method is based on a finite-frequency perturbation approach, through the measurement of a data-based sensitivity kernel. Experimental confirmation of the method is obtained using a cylindrical tank and an aggregate of ping-pong balls as targets surrounded by acoustic sources and receivers in a multistatic configuration. The spatial structure of the sensitivity kernel is constructed from field data for the target at a sparse set of positions, and compared with the expected theoretical structure. The localization of one or a few targets is demonstrated using the direct-path only. The experimental observations also show that the method benefits from including later arrivals from the tank wall and the bottom/surface reverberation, which indeed enhance the localization.

show abstract

Experimental measurement of the acoustic sensitivity kernel

Cited by 11 publications

References 9 publications

Inverting for a deterministic surface gravity wave using the sensitivity-kernel approach

Inverting for a deterministic surface gravity wave using the sensitivity-kernel approach

Quality of intrapartum care at Mulago national referral hospital, Uganda: clients’ perspective

Target localization through a data-based sensitivity kernel: A perturbation approach applied to a multistatic configuration

Contact Info

Product

Resources

About