Doppler Sonar Research Articles

Doppler sonar records of fish movement through a strong tidal stream: 3-months of observations from Grand Passage Nova Scotia

Coastal passages with strong tidal streams present potential for renewable energy generation with in-stream hydrokinetic turbines. However, there are concerns that these systems will lead to environmental impacts when marine life interact with moving turbine blades. We explore measurements of fish movement using Doppler current profilers as a way of quantifying the frequency of such interactions. Fish are detected in Doppler sonar data using calibrated backscatter levels in each of the four acoustic beams; by reprocessing un-averaged data it is possible to extract both fish and water velocities independently. We analyzed three months of Doppler sonar data collected in Grand Passage Nova Scotia from September until December 2014. The data show fish detections in large numbers for only a few days on three occasions at the deployment site. Most of the observations show fish moving at the same speed as the water but there are times when there is significant difference in fish and water speeds.

A method to address beam cross coupling errors in phased array Doppler sonar

Performance of Doppler sonar is degraded by beam cross coupling errors. This performance degradation presents itself as the loss of precision and bias of velocity estimates output by the system. A model is proposed here to reveal the physical essence of the beam cross coupling. Specifically, the model can analyze the effects of environmental conditions and vehicle attitude on the coupling bias. Based on this model, a phase assignment method is also proposed to reduce the beam cross coupling bias. The results obtained for various settings validate the efficacy of the proposed method.

A Preliminary Study on the Functionality of the Carotid-Vertebral Anastomotic Artery in the Regulation of Blood Flow in the Giraffe (Giraffa camelopardalis) by Duplex Ultrasound Examination

Postural change intermittently between upright and head down in giraffes standing at a height of 4.5 meters is of physiological significance. The length of a giraffe’s neck denotes the flow of blood against the force of gravity, to supply the brain over a 2 m distance. The force of gravity also affects the flow of blood toward the brain, with a posture change from erect to ground level. How do these changes in stance not result in fainting when the head is raised and brain damage when the head is lowered? Giraffe has an advanced interconnection of the common carotid artery and the vertebral artery. The connection is located at the midpoint of the atlas, as indicated by means of computerized tomography and dissection. Duplex ultrasound with Doppler waveform examination showed the unidirectional movement of blood with movement from the vertebral artery into the common carotid artery when the head is erect. The direction of flow allows the provision of blood to the maxillary artery that feeds the rostral epidural rete that supplies to the brain. The flow direction in the carotid-vertebral connection changes when blood moves in the direction of the head along with the force of gravity, when the head is lowered. The rerouting of blood to move from the common carotid into the vertebral artery prevents brain damage. We have confirmed, by utilizing a CT scan, Doppler sonar, and dissection of latex-filled arteries, the existence and blood flow direction within the anastomotic artery associated with variation in posture in the giraffe.

Alterations in deglutition in children with congenital Zika virus syndrome.

To characterize swallowing in children with congenital Zika virus syndrome in comparison to typical children. This cross-sectional study enrolled 45 children diagnosed with congenital Zika virus syndrome and 45 others with typical development. Swallowing was evaluated through clinical feeding evaluations Protocolo de Avaliação Clínica da Disfagia Pediátrica and using acoustic swallowing parameters (Doppler sonar). The mean age of children with congenital Zika virus syndrome was 26.69 ± 4.46 months and the mean head circumference was 29.20 ± 1.98 cm. Moderate/severe oropharyngeal dysphagia was found in 32(71.1%) of the children with congenital Zika virus syndrome. Significant differences were found between the groups on clinical evaluation: Children with congenital Zika virus syndrome presented insufficient lip closure 42(93.3%) and altered tonus of the tongue 35(77.8%) and cheeks 34(75.6%). In the children in the comparison group, only 6(13.3%) presented insufficient lip closure and 1(2.2%) had inadequate tongue posture. Changes during swallowing with liquid and spoonable food were not observed in the comparison group. When liquid/food was offered, affected children presented difficulties in sipping movements 14(77.8%) and lip/spoon contact 35(75%). The presence of residual food in the oral cavity after swallowing 38(86.4%) and clinical signs indicative of laryngotracheal penetration/aspiration, such as coughing, gagging and/or labored breathing, were also notable. No differences were found between the groups with regard to the acoustic parameters evaluated instrumentally. Children with congenital Zika virus syndrome present alterations in the oral phase of swallowing, as well as clinical signs indicative of pharyngeal phase impairment.

Acoustic analysis of swallowing sounds with the use of Sonar Doppler in premature babies during food transition

Objective: To define the acoustic parameters and the feasibility of using swallowing acoustic analysis as an auxiliary method for the transition from nasogastric or orogastric tube feeding to oral breastfeeding. Methodology: A cross-sectional study, which consisted of the following steps: 1. Data collection: Thirty-two newborns participated in this study (16 preterm and 16 full-term); 2. Clinical speech-language pathology evaluation: Clinical data were collected using Sonar Doppler used to assess the readiness of preterm infants to start oral feeding and swallowing sounds. Swallowing sounds were captured during breastfeeding and analyzed according to the frequency, intensity, and time of swallowing, as well as the pause time between swallows and the number of swallows. Results: The control and study groups presented significant differences in the mean wave time and swallowing per minute variables. Conclusion: Sonar Doppler, as an instrument used to capture sounds, is a viable auxiliary resource to evaluate the transition from nasogastric or orogastric tube to oral breastfeeding.

Acoustic analysis of swallowing as an auxiliary method for assessing dysphagia in Parkinson's disease

Objective: To measure the accuracy of DeglutiSom as an auxiliary method to assess swallowing in patients with Parkinson's disease (PD). Methodology: Accuracy study. Among 248 individuals, 91 participants met the inclusion criteria, with a mean age of 64.9 years (SD 7.7), 53.8% male and 46.2% female, with a mean disease duration of 12.6 years (SD 3.8 years). Two instrumental studies were performed: An acoustic analysis with Sonar Doppler via the DeglutiSom Software, and a videofluoroscopic swallow study. Three judges analyzed the swallowing sounds in the DeglutiSom software and the instrumental examination findings. Results: The inter-rater reliability was 90.1%, with 4.4% degree of partial agreement and 5.5% disagreement. Sensitivity resulted in 90.0% and specificity in 90.0%. A sensitivity of 97.0% and specificity of 91.0% are indicators of a high validity for the dysphagia screening method, with predictive value (+) of 97.0% and predictive value (-) of 91.0%, with an accuracy method of 96.0%. The validity indicator values for screening aspiration were also high, with a sensitivity of 90.0%, specificity of 90.0%, predictive value (+) of 82.0%, predictive value (-) of 95% , 0% and 90.0% accuracy. Conclusion: The method proposed is considered appropriate for oropharyngeal dysphagia and tracheal aspiration screening in patients with Parkinson's Disease.

Accuracy of Acoustic Evaluation of Swallowing as a Diagnostic Method of Dysphagia in Individuals Affected by Stroke: Preliminary Analysis.

After a stroke, more than half of the patients have some kind of disability, and dysphagia is frequently found. Cervical auscultation by Doppler sonar is an innovative technique with gain of credibility in the clinical evaluation of swallowing. To verify the diagnostic accuracy of Doppler sonar along with the DeglutiSom® software as an auxiliary method in the evaluation of oropharyngeal dysphagia in patients after stroke. The research is a cross-sectional, uncontrolled, blind, quantitative study with systematic random sampling. Patients from inpatient and outpatient units of a reference hospital with a stroke care unit were concomitantly submitted to both Doppler sonar and Fiberoptic Endoscopic Evaluation of Swallowing (FEES®). Seventy-three audio files collected from 26 patients through Doppler sonar were analyzed using DeglutiSom® software and confronted with the FEES® report, regarding three food consistencies offered to them during the exam. The study showed that the Doppler sonar correctly identified, among all the analyzed files, those that actually presented tracheal aspiration as well as it effectively identified patients who did not aspirate. The Youden index of 0.91 corroborates this information, showing a promising accuracy in detecting tracheal aspiration in the studied sample. The study evaluates the diagnostic accuracy of Doppler sonar, showing that it can be used as a valuable tool in the diagnosis of tracheal aspiration in patients after stroke. It is important to emphasize that the identification of residue by this method requires further studies. Also, larger sample size and more than one blind evaluator should be considered in future researches to increase the reliability of the proposed method.

Assessing Habitat Suitability for Native and Alien Freshwater Mussels in the River Waal (the Netherlands), Using Hydroacoustics and Species Sensitivity Distributions

Longitudinal training dams (LTDs) in the river Waal are novel river training structures that protect the littoral zone from the adverse effects of navigation providing new habitats for riverine macroinvertebrates. In order to inform river management and to better understand their ecological value for native and alien mussel species, it is important to assess the habitat suitability of the protected LTD shore channels. We applied spatial hydroacoustics surveys consisting of side-scan sonar (SSS) and acoustic Doppler current profiler (ADCP) of the substrate type, water depth and flow velocity in three shore channels in combination with species sensitivity distributions (SSDs) to predict habitat suitability for native and alien mussel species. SSDs allowed for the prediction of habitat suitability as a potentially occurring fraction (POF) of a species pool. High substrate type, water depth, and near-bottom flow velocity POFs were found for ≥ 70%, 100%, and 4–51% of the total shore channel area, respectively, suggesting that shore channels provide suitable habitat for both native and alien mussel species. To enhance the shore channels as habitat for native mussel species, we recommend increasing shallow areas dominated by fine (silt/clay) and sand substrate types with low near-bottom flow velocities (near 0 m/s). In contrast, the total area of hard substrate (e.g., boulders) in the shore channels should be reduced as it strongly favored invasive alien mussel species in our study. Future research should include additional abiotic parameters to enhance the habitat suitability predictions and compare the results for different riverine habitats.

Improved Velocity Estimation Method for Doppler Sonar Based on Accuracy Evaluation and Selection

The matched filtering method and the waveform-tracking method cannot maintain optimal velocity estimation performance all of the time. In order to solve this problem, this paper proposes an improved velocity estimation method for Doppler sonar, based on accuracy evaluation and selection. The echo of Doppler sonar is divided into several segments with the same width as the transmitted pulse, and each segment is regarded as the echo of the corresponding water layer. According to our study’s results, the velocity estimation accuracy of each segment is positively correlated with the ratio of its autocorrelation modulus to its power. Based on this conclusion, a velocity accuracy criterion with high accuracy and low complexity is designed in order to select the optimal velocity estimation for water layers or bottoms. The proposed accuracy selection method flexibly selects the echo interval to be processed according to the accuracy criterion, so as to maintain the optimal estimation of the current’s or bottom’s velocity. Water tank and field experiments using a prototype Doppler sonar device demonstrates that, compared with the matched filtering method and the waveform-tracking method, the average velocity estimation accuracy and bias of the proposed method are superior.

Pulse Coherent Doppler Profiler Measurement of Bedload Transport

AbstractPrior studies demonstrate that bottom velocity measurements from Doppler sonar systems are proportional to bedload transport rates. These observations suggest that acoustically based systems offer a capability for rapid sampling of bedload transport processes. Before these measurements can be fully utilized, validation and understanding of the sampling mechanism are essential. We explore the measurement mechanism through a series of laboratory trials with a field instrument, the multi‐frequency coherent Doppler profiler (MFDop). The MFDop system is a multi‐frequency (1.2–2.2 MHz), bistatic Doppler sonar that provides three‐component ensemble‐averaged velocity profiles over a ∼30 cm depth interval with up to 1 mm resolution at a rate of 50 profiles/sec. Tests of the MFDop system were carried out in the main flume in field‐scale conditions at the St. Anthony Falls Laboratory (SAFL) using 1 ms−1 mean flows over a mobile bed of sand with median grain size d50 = 0.4 mm. We find agreement between MFDop transport measurements and measurements based on bedform migration rates, and sediment traps built into the SAFL flume. Predictions using the Meyer‐Peter and Müller (1948) empirical equation closely match our observations while in contrast, predictions using the Nielsen (1992) equation are a factor of two higher.

Velocity Measurement of Coherent Doppler Sonar Assisted by Frequency Shift, Kalman Filter and Linear Prediction

Velocity is vital information for navigation and oceanic engineering. Coherent Doppler sonar is an accurate tool for velocity measurement, but its use is limited due to velocity ambiguity. Velocity measured by frequency shift has no velocity ambiguity, yet its measurement error is larger than that of coherent Doppler sonar. Therefore, coherent Doppler sonar assisted by frequency shift is used to accurately measure velocity without velocity ambiguity. However, the velocity measured by coherent Doppler sonar assisted by frequency shift is affected by impulsive noise. To decrease the impulsive noise, Kalman filter and linear prediction are proposed to improve the velocity sensing accuracy. In this method, the Kalman filter is used to decrease measurement error of velocity measured by frequency shift, and linear prediction is used to remove the impulsive noise generated by a wrong estimate of the integer ambiguity. Lab-based experiments were carried, and the results have shown that coherent Doppler sonar assisted by frequency shift, Kalman filter and linear prediction can provide accurate and precise velocity with short time delay in a large range of signal to noise ratio.

Acoustic Robust Velocity Measurement Algorithm Based on Variational Bayes Adaptive Kalman Filter

Acoustic Doppler velocity logs or acoustic Doppler current profilers, herein referred to as Doppler sonar, are important types of oceanographic instruments, which have been extensively used over the past 30 years. The precision of Doppler sonar is an important technical specification, which is a statement of velocity random error that partially or entirely averages out over a long period of time. This article focuses on acoustic robust velocity processing algorithm based on variational Bayes adaptive Kalman (VBAK) filter, known as the real-time estimation of velocity statistical characteristics, which may be contaminated by some unknown and nonstationary noise. It aims to solve the problem that the precision of the Doppler sonar is prone to be affected by the marine environment. The theory, simulation, and experimental results are compared with the standard Kalman filter algorithm. It shows that the VBAK algorithm may obtain a reasonable estimate of velocity even in the case of steep slope over 15° and the precision is effectively improved.

Acoustic analysis of swallowing sounds in tracheostomized patients affected by traumatic brain injury

ABSTRACT Purpose: to demonstrate the feasibility of using the acoustic analysis of swallowing sounds as a combined method in the clinical assessment of tracheostomized patients affected by traumatic brain injury. Methods: an observational, cross-sectional study. A total of 10 adult patients, in the mean age of 43.6 years, participated. They were hospitalized in wards, semi-intensive, or intensive care units, from May to July 2016. The inclusion criterion involved being affected by traumatic brain injury, confirmed with a CT scan. The Speech Therapy Tracheal Decannulation Protocol was used in the clinical assessment, as well as the cervical auscultation with the Doppler sonar. Fisher’s test was used, resulting in no significant relationship (p > 0.05) between the variables analyzed in the two consistencies and decannulation. Results: the presence of an acoustic signal of laryngeal elevation was observed, as well as noise between the swallowings, and acoustic signal suggestive of residue in 50% of the patients for the consistencies tested. When the peak frequency, mean wave time, presence of residue in between swallowings, and acoustic signal suggestive of residues were correlated with decannulation (Table 5), no significant correlation was verified (p > 0.05) between the variables analyzed in the two consistencies and the decannulation. Conclusion: the study suggests that it is feasible to use the Doppler sonar as a combined method in the clinical assessment of dysphagia for the decannulation of patients affected by traumatic brain injury.

Relation between acoustic analysis of swallowing and the presence of pharyngeal residue and penetration/aspiration in resistant hypertensive patients with obstructive sleep apnea

ABSTRACT Purpose: to evaluate the relationship between acoustic analysis of swallowing sounds and the presence of pharyngeal residue and penetration/aspiration detected by fiberoptic endoscopic evaluation of swallowing in resistant hypertensive patients with obstructive sleep apnea. Methods: an observational study in which resistant hypertensive individuals diagnosed with obstructive sleep apnea participated through the all-night polysomnography exam. The participants underwent an acoustic analysis of swallowing sounds, using a Doppler sonar and simultaneously a fiberoptic endoscopic evaluation of swallowing. The acoustic parameters analyzed were initial frequency, initial intensity, first peak frequency, second peak frequency, final intensity and swallowing time. Independent samples of t-test and Mann-Whitney test were used for statistical analysis. The level of statistical significance adopted was 5%. Results: eighty five participants with average age of 58.3±6.3 years were evaluated. There was a statistically significant difference between groups with and without pharyngeal residue, in relation to the following parameters of swallowing acoustic signal: initial frequency and intensity, second peak frequency, final intensity and swallowing time. Only 10 milliliters of pudding consistency showed a statistically significant difference in the second peak frequency of the acoustic signal of swallowing between groups with and without penetration/aspiration. Conclusion: a relationship between measurements of swallowing acoustic signal and pharyngeal residue in this population was found, but not between swallowing sounds and penetration/aspiration.

SwathDop: Multibeam Pulse-Coherent Doppler Sonar for Scanning 2D Velocity Sections near the Sediment–Water Interface

AbstractThis paper considers the problem of accurately measuring the sediment transport over bedforms where flow evolves continuously both in time and space. For this purpose, we have developed a pulse-to-pulse coherent Doppler sonar system designed in bistatic geometry with two fan-beam transmitters symmetrically positioned on each side of a multielement receive array. The system resolves 2D velocity components within a ±20° (~0.5 m by ~0.5 m) swath. The software-defined radio data acquisition and control system limited us at present to eight independent receiver channels, and consequently the azimuthal resolution of the system is 4°. As a preliminary test of the sonar system, the system operation was simulated using a model developed to predict coherent sonar performance. The uncertainties with respect to the prescribed values and mean measurements in the model results were confined to 0.35 and 0.23 cm s−1, respectively, in the presence of strong shear (~150 s−1) and 50 cm s−1 horizontal flow. An important thing is that the model allowed us to test and develop the signal processing algorithms necessary to invert the multibeam sonar data. Using sand of 0.4-mm median diameter, the laboratory trials were carried out in active sediment transport conditions over dunes with 2-m wavelength and ~0.90 m s−1 unidirectional flow velocities. The results presented here focus mainly on 2D velocity field and indicate an average 4% deviation from the wake law and 8% from independent observations made with the wide-band multifrequency coherent Doppler profiler (MFDop) instrument under similar flow conditions.

Robust Resolution of Velocity Ambiguity for Multifrequency Pulse-to-Pulse Coherent Doppler Sonars

Pulse-to-pulse coherent Doppler sonars are widely used to explore boundary layer characteristics of oceans. Multifrequency pulse-to-pulse coherent Doppler sonars have been proposed in the literature to tackle the velocity ambiguity problem faced by single-frequency systems. A robust algorithm for resolving the velocity ambiguity is crucial in such systems. This paper proposes a method based on the robust Chinese remainder theorem to resolve the velocity ambiguity for multifrequency pulse-to-pulse coherent Doppler sonars. We evaluate the proposed method for resolving the velocity ambiguity in terms of the trial fail rate. The simulations show that the proposed method achieves 1/8 trial failure rate as the reference method. A theoretical criterion is also derived to support the observation that in most cases our proposed method is more robust to estimation errors than the reference method.

Quantifying Long-Term Accuracy of Sonar Doppler Velocity Logs

A Doppler velocity log sonar measures relative velocity between the instrument and the bottom of a body of water by transmitting acoustic pulses that are scattered off the bottom. The scattered sound is received and the Doppler shift is measured. Like any other sensor, the data quality of a Doppler velocity log can be quantified by a variance and a bias. The goal of this work is to model error sources that do not average out over time; quantify those sources under various operating and environmental conditions; and derive a statistically significant range of expected long-term errors. The following error sources are analyzed: absorption bias, terrain bias, sidelobe coupling, beam alignment, clock drift, element spacing, and speed-of-sound error. A combination of analytical derivations and simulations, where the simulation results were fit to closed-form equations, were used to construct the long-term error model. Validity of the error model was demonstrated by tank testing Doppler velocity logs of different configurations under a range of operating conditions. We envision that the error model derived in this work will be of great use to both system designers that engage in design of new instruments and instrument users that wish to understand how to achieve high navigational accuracy during missions.

Observations of turbulent kinetic energy dissipation at the Labrador Sea surface layer

We present an analysis of turbulent kinetic energy dissipation rates in the upper ocean using in situ measurements collected by a coherent Doppler sonar in the Labrador Sea during summer 2004. The sonar recorded horizontal velocity fluctuations of the upper 2 m with an uncommonly small spatial resolution of 0.8 cm, allowing direct calculations of wavenumber spectra and the application of Kolmogorov theory to obtain turbulent kinetic energy dissipation rates for the first time in this area. The project presented a unique opportunity for the study of air–sea exchange during a phytoplankton bloom, being the first time a specialized air–sea interaction spar buoy was deployed during such particular event. An additional uniqueness of this experiment resulted from being the first turbulent kinetic energy dissipation rate observations obtained at higher latitudes, coincidentally in a well-known region of dense water formation, with a fundamental role in both global circulation and forecasting studies of global climate change. Focusing on the relationship between turbulent kinetic energy dissipation rates and wave phase in the upper 2 m, we estimated O[Formula: see text] turbulent kinetic energy dissipation rates, consistent with previous estimates obtained through similar devices and methods. A T-test between dissipation rates calculated at the crest and at the trough of waves showed no dependency of turbulent kinetic energy dissipation rates on the wave phase at 2 m depth, coinciding with many of the earlier findings available. a comparison with previous research showing conflicting results with our values is also discussed here linking them to the relative roles of experimental design variations, diverse dynamical frames, and particular environmental conditions.

Food Intake Detection Using Ultrasonic Doppler Sonar

Reliable, user-friendly and convenient sensing is highly desirable when the continuous monitoring of food intake is necessary. In this paper, food intake monitoring was during the processes of chewing and swallowing. Acoustic Doppler sonar (ADS) detected chewing and swallowing events that were non-contact and free from acoustic interference. When a 40 kHz ultrasonic beam was focused on the lower jaw and neck, movements of the chin and neck cause Doppler frequency shifts and an amplitude envelope modulation of ultrasonic signals. Hence, it was possible to detect chewing and swallowing events using Doppler frequency shifts in the received ultrasound signals. To prevent suspicious chew events caused by talking from being recognized as food intake events, the log-filter bank energy of the voice band was also taken into consideration. Automatic detection of chewing and swallowing events was achieved via an artificial neural network. The experimental results showed that the proposed ADS-based food intake detection method yielded promising results with maximum recognition rates of 91.4% and 78.4% for chewing and swallowing, respectively. As a result, it was confirmed that the proposed food intake detection method using ultrasonic Doppler yielded high rates of recognition without discomfort to the user from continuous skin contact.

ドップラーソナーの最新動向( 航法システム研究会・新技術)

ドップラーソナーの最新動向( 航法システム研究会・新技術)