Marine seismic surveys with vector acoustic sensors

Rodríguez

The Journal of the Acoustical Society of America

et al. 2010

This paper proposes a vector sensor measurement model and the related Bartlett estimator based on particle velocity measurements for generic parameter estimation, illustrating the advantages of the Vector Sensor Array ͑VSA͒. A reliable estimate of the seabed properties such as sediment compressional speed, density and compressional attenuation based on matched-field inversion ͑MFI͒ techniques can be achieved using a small aperture VSA. It is shown that VSAs improve the resolution of seabed parameter estimation when compared with pressure sensor arrays with the same number of sensors. The data considered herein was acquired by a four-element VSA in the 8-14 kHz band, during the Makai Experiment in 2005. The results obtained with the MFI technique are compared with those obtained with a method proposed by C. Harrison, which determines the bottom reflection loss as the ratio between the upward and downward beam responses. The results show a good agreement and are in line with the historical information for the area. The particle velocity information provided by the VSA increases significantly the resolution of seabed parameter estimation and in some cases reliable results are obtained using only the vertical component of the particle velocity.

Section: Introductionmentioning

confidence: 99%

“…[1][2][3][4][5][6][7][8] Nehorai and Paldi 1 extended an analytical model, initially developed for electromagnetic sources, to the underwater acoustic case. The comparison of the DOA estimation performance of a VSA and that of an array of pressure sensors shows the advantages of the VSA.…”

Section: Introductionmentioning

confidence: 99%

Seabed geoacoustic characterization with a vector sensor array

Rodríguez

The Journal of the Acoustical Society of America

et al. 2010

“…Increased spatial filtering capabilities gave rise to new applications where the VSA could be used with advantage over hydrophone arrays. Due to these characteristics the VSA is appearing in different fields like port and waterway security [5], underwater communications [6], underwater acoustic tomography and geoacoustic inversion [7,8]. The bottom parameter estimation results [9,10] using high-frequency signals acquired by the VSA during the Makai Ex 2005 are of considerable interest due to their uniqueness in this research area.…”

Section: Contribution To Technological Innovationmentioning

confidence: 99%

Vector Sensor Arrays in Underwater Acoustic Applications

IFIP Advances in Information and Communication Technology

Jesus

2010

Abstract. Traditionally, ocean acoustic signals have been acquired using hydrophones, which measure the pressure field and are typically omnidirectional. A vector sensor measures both the acoustic pressure and the three components of particle velocity. Assembled into an array, a vector sensor array (VSA) improves spatial filtering capabilities when compared with arrays of same length and same number of hydrophones. The objective of this work is to show the advantage of the use of vector sensors in underwater acoustic applications such as direction of arrival (DOA) estimation and geoacoustic inversion. Beyond the improvements in DOA estimation, it will be shown the advantages of using the VSA in bottom parameters estimation. Additionally, is tested the possibility of using high frequency signals (say 8-14 kHz band), acquired during the MakaiEx 2005, to allow a small aperture array, reducing the cost of actual sub-bottom profilers and providing a compact and easy-to-deploy system.

Acoustic Pressure and Particle Velocity for Spatial Filtering of Bottom Arrivals

Jesus

2019

IEEE J. Oceanic Eng.

This paper discusses the advantages of using a combination of acoustic pressure and particle velocity motion for filtering bottom arrivals. A possible area of application is reflection seismology where, traditionally, the seismic image is extracted from the bottom-reflected broadband acoustic signals received on hydrophones. Since hydrophones are omnidirectional in nature, the received bottom returns are often contaminated by waterborne signals, sea surface reflections, and noise. A substantial part of the processing of the data is dedicated to filtering out these unwanted signals. Today, vector sensors allow us to measure both acoustic pressure and particle velocity motion in a single and compact sensor. The combination of pressure and particle velocity measured at a single location or particle velocity and particle velocity gradient at closely spaced locations allows for spatial beam steering to predetermined directions and filter out unwanted replicas from other directions. Moreover, this can be done at the sensor level, dramatically decreasing the offline processing. The spatial filtering capabilities of various pressure-pressure, particle velocity-particle velocity, and pressure-particle velocity combinations are analyzed in view of filtering the bottom arrivals. It is shown that the combination of pressure and vertical particle velocity and, particularly, the combination of vertical particle velocity and particle velocity gradient enhance bottom arrivals. Moreover, a simple steering procedure combining pressure and particle velocity components of a triaxial sensor allows us to determine the tridimensional structure of the acoustic field and the separation of the bottom reflections. The spatial selectivity of the various sensor combinations is shown with simulations and verified with experimental data acquired with 10 cm separated vector sensors in the 800-1250-Hz band, during the Makai 2005 sea trial, off Kauai Island, HI, USA.