Research

20 pages, 7905 KiB

Open AccessArticle

Through-Ice Acoustic Source Tracking Using Vision Transformers with Ordinal Classification

by Steven Whitaker, Andrew Barnard, George D. Anderson and Timothy C. Havens

Sensors 2022, 22(13), 4703; https://0-doi-org.brum.beds.ac.uk/10.3390/s22134703 - 22 Jun 2022

Cited by 1 | Viewed by 1369

Ice environments pose challenges for conventional underwater acoustic localization techniques due to their multipath and non-linear nature. In this paper, we compare different deep learning networks, such as Transformers, Convolutional Neural Networks (CNNs), Long Short-Term Memory (LSTM) networks, and Vision Transformers (ViTs), for [...] Read more.

Ice environments pose challenges for conventional underwater acoustic localization techniques due to their multipath and non-linear nature. In this paper, we compare different deep learning networks, such as Transformers, Convolutional Neural Networks (CNNs), Long Short-Term Memory (LSTM) networks, and Vision Transformers (ViTs), for passive localization and tracking of single moving, on-ice acoustic sources using two underwater acoustic vector sensors. We incorporate ordinal classification as a localization approach and compare the results with other standard methods. We conduct experiments passively recording the acoustic signature of an anthropogenic source on the ice and analyze these data. The results demonstrate that Vision Transformers are a strong contender for tracking moving acoustic sources on ice. Additionally, we show that classification as a localization technique can outperform regression for networks more suited for classification, such as the CNN and ViTs. Full article

(This article belongs to the Special Issue Underwater Acoustic Sensors and Applications)

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14 pages, 9384 KiB

Open AccessArticle

Experimental Results of Underwater Acoustic Communication with Nonlinear Frequency Modulation Waveform

by Jeongha An, Hyungin Ra, Changhyun Youn and Kiman Kim

Sensors 2021, 21(21), 7194; https://0-doi-org.brum.beds.ac.uk/10.3390/s21217194 - 29 Oct 2021

Cited by 7 | Viewed by 2193

Abstract

In this paper, we propose underwater acoustic (UWA) communications using a generalized sinusoidal frequency modulation (GSFM) waveform, which has a distinct ambiguity function (AF) and correlation function characteristic. For these reasons, it is more robust in multipath channels than the conventional chirp spread [...] Read more.

In this paper, we propose underwater acoustic (UWA) communications using a generalized sinusoidal frequency modulation (GSFM) waveform, which has a distinct ambiguity function (AF) and correlation function characteristic. For these reasons, it is more robust in multipath channels than the conventional chirp spread spectrum (CSS) with a linear frequency modulation (LFM) waveform. Four types of GSFM waveforms that are orthogonal to each other are applied for each symbol in the proposed method. To evaluate the performance of the proposed method, we compared the performances of the proposed method and conventional method by conducting diverse experiments: simulations, lake trials and sea trials. In the simulation results, the proposed method shows better performance than the conventional method. The lake trial was conducted with a distance of 300~400 m between the transmitter and receiver. As a result of the experiment, the average bit error rate (BER) of the proposed method is

3.52 \times 10^{- 2}

and that of the conventional method is

3.52 \times 10^{- 1}

, which shows that the proposed method is superior to the conventional method. The sea trial was conducted at a distance of approximately 20 km between the transmitter and receiver at a depth of 1500 m, and the receiver was composed of 16 vertical line arrays (VLAs) with a hydrophone. The proposed method had a BER of

0.3 \times 10^{- 2}

in one channel and was error free in the other. Full article

(This article belongs to the Special Issue Underwater Acoustic Sensors and Applications)

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22 pages, 7609 KiB

Open AccessArticle

Monitoring of Caged Bluefin Tuna Reactions to Ship and Offshore Wind Farm Operational Noises

by Vicente Puig-Pons, Ester Soliveres, Isabel Pérez-Arjona, Victor Espinosa, Pedro Poveda-Martínez, Jaime Ramis-Soriano, Patricia Ordoñez-Cebrián, Marek Moszyński, Fernando de la Gándara, Manuel Bou-Cabo, José L. Cort and Eladio Santaella

Sensors 2021, 21(21), 6998; https://0-doi-org.brum.beds.ac.uk/10.3390/s21216998 - 21 Oct 2021

Cited by 1 | Viewed by 2466

Abstract

Underwater noise has been identified as a relevant pollution affecting marine ecosystems in different ways. Despite the numerous studies performed over the last few decades regarding the adverse effect of underwater noise on marine life, a lack of knowledge and methodological procedures still [...] Read more.

Underwater noise has been identified as a relevant pollution affecting marine ecosystems in different ways. Despite the numerous studies performed over the last few decades regarding the adverse effect of underwater noise on marine life, a lack of knowledge and methodological procedures still exists, and results are often tentative or qualitative. A monitoring methodology for the behavioral response of bluefin tuna (Thunnus thynnus) when exposed to ship and wind turbine operational noises was implemented and tested in a fixed commercial tuna feeding cage in the Mediterranean sea. Fish behavior was continuously monitored, combining synchronized echosounder and video recording systems. Automatic information extracted from acoustical echograms was used to describe tuna reaction to noise in terms of average depth and vertical dimensions of the school and the indicators of swimming speed and tilt direction. Video recordings allowed us to detect changes in swimming patterns. Different kinds of stimuli were considered during bluefin tuna cage monitoring, such as noise generated by feeding boats, wind farm operational noise, and other synthetic signals projected in the medium using a broadband underwater projector. The monitoring system design was revealed as a successful methodological approach to record and quantify reactions to noise. The obtained results suggested that the observed reactions presented a strong relationship with insonification pressure level and time. Behavioral changes associated with noise are difficult to observe, especially in semi-free conditions; thus, the presented approach offered the opportunity to link anthropogenic activity with possible effects on a given marine species, suggesting the possibility of achieving a more realistic framework to assess the impacts of underwater noise on marine animals. Full article

(This article belongs to the Special Issue Underwater Acoustic Sensors and Applications)

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15 pages, 1722 KiB

Open AccessArticle

Assessment of Arrow-of-Time Metrics for the Characterization of Underwater Explosions

by Ramón Miralles, Guillermo Lara, Alicia Carrión and Manuel Bou-Cabo

Sensors 2021, 21(17), 5952; https://0-doi-org.brum.beds.ac.uk/10.3390/s21175952 - 04 Sep 2021

Cited by 2 | Viewed by 1827

Abstract

Anthropogenic impulsive sound sources with high intensity are a threat to marine life and it is crucial to keep them under control to preserve the biodiversity of marine ecosystems. Underwater explosions are one of the representatives of these impulsive sound sources, and existing [...] Read more.

Anthropogenic impulsive sound sources with high intensity are a threat to marine life and it is crucial to keep them under control to preserve the biodiversity of marine ecosystems. Underwater explosions are one of the representatives of these impulsive sound sources, and existing detection techniques are generally based on monitoring the pressure level as well as some frequency-related features. In this paper, we propose a complementary approach to the underwater explosion detection problem through assessing the arrow of time. The arrow of time of the pressure waves coming from underwater explosions conveys information about the complex characteristics of the nonlinear physical processes taking place as a consequence of the explosion to some extent. We present a thorough review of the characterization of arrows of time in time-series, and then provide specific details regarding their applications in passive acoustic monitoring. Visibility graph-based metrics, specifically the direct horizontal visibility graph of the instantaneous phase, have the best performance when assessing the arrow of time in real explosions compared to similar acoustic events of different kinds. The proposed technique has been validated in both simulations and real underwater explosions. Full article

(This article belongs to the Special Issue Underwater Acoustic Sensors and Applications)

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18 pages, 3964 KiB

Open AccessArticle

Design and Analysis of an Active Reflection Controller That Can Reduce Acoustic Signal Refer to the Angle of Incidence

by Joo Young Pyun, Beom Hoon Park, Young Hun Kim, Yeong Bae Won, Hak Yi, Jeong-Min Lee, Hee-Seon Seo and Kwan Kyu Park

Sensors 2021, 21(17), 5793; https://0-doi-org.brum.beds.ac.uk/10.3390/s21175793 - 28 Aug 2021

Cited by 3 | Viewed by 1954

Abstract

Techniques for reducing the reflection of acoustic signals have recently been actively studied. Most methods for reducing acoustic signals were studied using the normal-incidence wave reduction technique. Although the technique of canceling an object from the normal incidence wave is essential, research on [...] Read more.

Techniques for reducing the reflection of acoustic signals have recently been actively studied. Most methods for reducing acoustic signals were studied using the normal-incidence wave reduction technique. Although the technique of canceling an object from the normal incidence wave is essential, research on reducing acoustic signals according to the angle of incidence is required for practical applications. In this study, we designed, fabricated, and experimented with an active reflection controller that can reduce acoustic signals according to the angle of incidence. The controller consists of a transmitter on one layer, a receiver sensor on two layers, and an acoustic window on three layers. To reduce the reflected signal, a combination of the time delay and phase was applied to the controller to minimize the acoustic signal by up to −23 dB at an angle of 10°. A controller array simulation was performed based on the results of a controlled experiment. In conclusion, our proposed controller can reduce acoustic signals according to the angle of incidence, which makes it suitable for many applications. Full article

(This article belongs to the Special Issue Underwater Acoustic Sensors and Applications)

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11 pages, 4783 KiB

Open AccessCommunication

Comparative Experimental Investigation on Optimal Parametric Array Types

by Donghwan Jung, Jiyoung Song, Jeasoo Kim and Jaehyuk Lee

Sensors 2021, 21(15), 5085; https://0-doi-org.brum.beds.ac.uk/10.3390/s21155085 - 27 Jul 2021

Cited by 2 | Viewed by 1973

Abstract

As a sound transmitting device that relies on the nonlinearity of a medium, a parametric array (PA) can generate high-directivity low-frequency signals using a small aperture transducer and high-frequency signals. Despite their relatively low source level, the PA is frequently used to measure [...] Read more.

As a sound transmitting device that relies on the nonlinearity of a medium, a parametric array (PA) can generate high-directivity low-frequency signals using a small aperture transducer and high-frequency signals. Despite their relatively low source level, the PA is frequently used to measure the acoustic properties of materials in low-frequency regions owing to their high directivity in confined acoustic water tanks. Therefore, methods for improving the source level of secondary signals are of interest. Currently, there are two driving methods for PA: the dual-frequency PA and the broadband PA with amplitude modulation. In this study, we share the results of an elaborate and comparative experimental investigation of these two driving methods. Comparisons are made and discussed in terms of the intensity of the generated secondary signal and its characteristics in the frequency domain. Based on these factors, we confirmed that the broadband PA was more suitable as the sound source of the low-frequency characteristic measurement system of acoustic materials. Full article

(This article belongs to the Special Issue Underwater Acoustic Sensors and Applications)

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13 pages, 4575 KiB

Open AccessArticle

Passive Source Localization Using Acoustic Intensity in Multipath-Dominant Shallow-Water Waveguide

by Sunhyo Kim, Sungho Cho, Seom-kyu Jung and Jee Woong Choi

Sensors 2021, 21(6), 2198; https://0-doi-org.brum.beds.ac.uk/10.3390/s21062198 - 21 Mar 2021

Cited by 1 | Viewed by 2258

Abstract

The array invariant technique has been recently proposed for passive source localization in the ocean. It has successfully estimated the source–receiver horizontal range in multipath-dominant shallow-water waveguides. However, it requires a relatively large-scale hydrophone array. This study proposes an array invariant method that [...] Read more.

The array invariant technique has been recently proposed for passive source localization in the ocean. It has successfully estimated the source–receiver horizontal range in multipath-dominant shallow-water waveguides. However, it requires a relatively large-scale hydrophone array. This study proposes an array invariant method that uses acoustic intensity, which is a vector quantity that has the same direction as the sound wave propagating through a water medium. This method can be used to estimate not only the source–receiver horizontal range, but also the azimuth to an acoustic source. The feasibility of using a vector quantity for the array invariant method is examined through a simulation and an acoustic experiment in which particle velocity signals are obtained using a finite difference approximation of the pressure signals at two adjacent points. The source localization results estimated using acoustic intensity are compared with those obtained from beamforming of the acoustic signals acquired by the vertical line array. Full article

(This article belongs to the Special Issue Underwater Acoustic Sensors and Applications)

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14 pages, 6174 KiB

Open AccessCommunication

Research and Fabrication of Broadband Ring Flextensional Underwater Transducer

by Jiuling Hu, Lianjin Hong, Lili Yin, Yu Lan, Hao Sun and Rongzhen Guo

Sensors 2021, 21(4), 1548; https://0-doi-org.brum.beds.ac.uk/10.3390/s21041548 - 23 Feb 2021

Cited by 6 | Viewed by 2983

Abstract

At present, high-speed underwater acoustic communication requires underwater transducers with the characteristics of low frequency and broadband. The low-frequency transducers also are expected to be low-frequency directional for realization of point-to-point communication. In order to achieve the above targets, this paper proposes a [...] Read more.

At present, high-speed underwater acoustic communication requires underwater transducers with the characteristics of low frequency and broadband. The low-frequency transducers also are expected to be low-frequency directional for realization of point-to-point communication. In order to achieve the above targets, this paper proposes a new type of flextensional transducer which is constructed of double mosaic piezoelectric ceramic rings and spherical cap metal shells. The transducer realizes broadband transmission by means of the coupling between radial vibration of the piezoelectric rings and high-order flexural vibration of the spherical cap metal shells. The low-frequency directional transmission of the transducer is realized by using excitation signals with different amplitude and phase on two mosaic piezoelectric rings. The relationship between transmitting voltage response (TVR), resonance frequency and structural parameters of the transducer is analyzed by finite element software COMSOL. The broadband performance of the transducer is also optimized. On this basis, the low-frequency directivity of the transducer is further analyzed and the ratio of the excitation signals of the two piezoelectric rings is obtained. Finally, a prototype of the broadband ring flextensional underwater transducer is fabricated according to the results of simulation. The electroacoustic performance of the transducer is tested in an anechoic water tank. Experimental results show that the maximum TVR of the transducer is 147.2 dB and the operation bandwidth is 1.5–4 kHz, which means that the transducer has good low-frequency, broadband transmission capability. Meanwhile, cardioid directivity is obtained at 1.4 kHz and low-frequency directivity is realized. Full article

(This article belongs to the Special Issue Underwater Acoustic Sensors and Applications)

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