Analytical discussion of past measurements of acoustic attenuation in mud sediments and of possible future experimental approaches

Pierce, Allan D.; Siegmann, William L.; Brown, Elisabeth M.

doi:10.1121/2.0000221

Cited by 4 publications

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“…Attenuation measurements were reported in [1], [3], [4], and [31]. It has been shown that reliable attenuation records are challenging to obtain in mud due to primitive techniques and complication from ambient noise [33]. With limited understanding and measurement of the geoacoustic properties in mud, sediment acoustic modeling is currently an ongoing research topic [34].…”

Section: Introductionmentioning

confidence: 99%

Measurement of Sound Speed in Fine-Grained Sediments During the Seabed Characterization Experiment

Yang

Jackson

2020

IEEE J. Oceanic Eng.

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The Seabed Characterization Experiment was carried out from March 5 to April 10, 2017 (SBCEX17) on the New England Mud Patch, approximately 90 km south of Martha's Vineyard. The SBCEX17 experimental site covers an area of 11 km × 30 km with water depth in the range of 75-80 m. The Sediment Acoustic-speed Measurement System (SAMS) is designed to measure sediment sound speed and attenuation simultaneously over the surficial 3 m of sediments. During SBCEX17, SAMS was successfully deployed at 18 sites, which were chosen to coincide with coring locations, with the goal of developing a geoacoustic model for the study area. In this article, a summary of SAMS operation during SBCEX17 is presented, as well as preliminary results for sediment sound speed and its spatial variation in the frequency band of 2-10 kHz. It is found that in mud, the sound-speed ratio is in the range of 0.98-1. Little dispersion was observed in this frequency band. Using the preliminary SAMS sound-speed results measured at different depths, the sound-speed gradient in mud within the surficial 3 m favors an exponential rather than a linear dependence at SBCEX17 site. Large gradients are observed for depth shallower than 1.5 m. For the sandy basement beneath the mud layer, the sound-speed ratio is as high as 1.105.

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Section: Introductionmentioning

confidence: 99%

Measurement of Sound Speed in Fine-Grained Sediments During the Seabed Characterization Experiment

Yang

Jackson

2020

IEEE J. Oceanic Eng.

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“…Section 2 Potential flow visualization techniques in mud), knowledge of acoustic properties of mud are also required to allow estimation of the maximum depth to which images of adequate quality can still be produced. Other research related to the acoustic properties of mud, like Pierce et al (2015), mention however the lack of any available and trustworthy data. Measurements to determine the acoustic properties of mud are therefore required to fully evaluate the potential of ultrasonography.…”

Section: Ultrasonographymentioning

confidence: 99%

Assessment of the potential of radiography and ultrasonography to record flow dynamics in cohesive sediments (mud)

Brouwers

Beeck²,

Meire³

et al. 2022

Front. Earth Sci.

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The possible use of both radiography and ultrasonography to visualise flow dynamics in cohesive sediments, also known as fluid mud, has been assessed. Ultimately, these techniques are intended to enable the application of Particle Image Velocimetry (PIV) in experimental fluid dynamics using such fluid mud. This research takes into account the specific requirements arising from this objective. Those requirements are primarily penetration depth, adequate frame rate and the preference not to seed with tracer particles. The evaluation of both techniques is elaborated in detail based the properties of mud originating from the Port of Zeebrugge (Belgium). The assessment of radiography starts with a chemical element analysis of the fluid mud, the results of which are used to determine the attenuation for high-energy electromagnetic radiation. Using various research software, the maximum thickness of the mud layer could be determined as a function of the maximum recordable flow velocities for different radiation sources. However, for the flow velocities expected in nautical research experiments, these thicknesses proved insufficient. Supplemented by the results of a particle size distribution analysis, it is found that high frequency ultrasound radiation will scatter in mud. In case of a great number of scatterers, the scattered ultrasound waves will interact, eventually resulting in speckle images, which are ideally suited for tracking. These findings were confirmed in a test setup with a standard medical ultrasound scanner. The penetration depth of ultrasonography with standard medical equipment is also limited. However, since ultrasonography is based on reflection, this is less of an issue compared to radiography, for which full penetration of the mud layer is required. Ultrasonography is therefore suggested as the preferred technique for the intended application.

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“…14) in 1964 by Wood and Weston [17] had intrinsic value and that modern techniques might yield better values for the frequency-dependent attenuation. The revised deductions [18] are given in the second column of the table in Fig. 15, Figure 15: Attenuation values as inferred from the Wood and Weston data.…”

Section: Attenuation Of Sound In Mudmentioning

confidence: 99%

Suggested methodology for direct and inverse characterization of marine sediments that contain mud

Pierce¹,

Siegmann²,

Brown³

2016

Proceedings of Meetings on Acoustics

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The measurement and prediction of compressional wave speeds and attenuation in mud sediments are discussed. The principal defining properties are due to clay particles within the mud. Because such particles carry electrical charges, theories for sandy/silty sediments are not applicable.. The mixture theory of Mallock and Wood works moderately well and, because of the high porosity, predicts that the sound speed is less than that for sea water. Data implying substantially higher sound speeds should be carefully assessed. Theory also predicts monotonic increase of sound speed with frequency, so data contrary to this should also be assessed. A correction to the Mallock-Wood formulation that includes electrostatic pressure within the mud raises the sound speed by 1%, and this explains some data assembled by Jackson and Richardson and explains the shift in the minimum in the sound speed versus density curve discovered by Holland. Large discrepancies in the measured values of attenuation are reviewed, and it is suggested that the reasons for such be found. The rudimentary theory under development needs experimental guidance, but seems valid in its predictions that the attenuation must vary as the square of frequency at low frequencies and, in any event, increases monotonically with increasing frequency.

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Analytical discussion of past measurements of acoustic attenuation in mud sediments and of possible future experimental approaches

Cited by 4 publications

References 0 publications

Measurement of Sound Speed in Fine-Grained Sediments During the Seabed Characterization Experiment

Measurement of Sound Speed in Fine-Grained Sediments During the Seabed Characterization Experiment

Assessment of the potential of radiography and ultrasonography to record flow dynamics in cohesive sediments (mud)

Suggested methodology for direct and inverse characterization of marine sediments that contain mud

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