Underwater Listening Research Articles

Boundary Pass Underwater Listening Station—Data management and processing

The Boundary Pass Underwater Listening Station, sponsored by Transport Canada, Port of Vancouver and JASCO Applied Sciences, has continuously operated two compact tetrahedral hydrophone arrays beneath the busy shipping lanes leading to Vancouver, Canada since June 2020. The arrays are deployed 300 m apart on the seabed at 190 m depth and are cabled 2.6km to shore. A high sample rate of 512 kHz on all eight channels, with 24-bit samples, produces almost 400 TB/yr of raw acoustic data. Automated real-time data analysis calculates ambient noise statistics, detects marine mammal sounds, measures underwater radiated noise of individual ships, and creates spatial noise maps of the hulls of some vessels passing closely overhead. The derived data products are stored in an easy-to-maintain online database of just a few TB/yr. Results in graphic, tabular and compressed audio formats are made available to scientists and project managers through an intuitive web interface. The project follows international standards for ship noise and ambient noise calculations, so the results can be compared with measurements made elsewhere.

Cellulose Gel Mechanoreceptors – Principles, Applications and Prospects

AbstractIn order to effectively harness varieties of mechanical waves or vibrations for the purpose of monitoring and/or powering, developments in responsive materials and conversion technologies are taking place driven by the world's current and future demands. One of the most popular novelties of the last two decades is represented by hydrogel‐ or ionogel‐based flexible iontronics which constitute a wide family of innovative smart (self‐powered) mechanoreceptors relevant for various applications such as personal health care, identity and safety monitoring, intelligent human‐machine operation interfaces, underwater listening and communication, and so on. Cellulosic gels (CGs), as a promising green substitute for fossil fuel‐derived materials, are extensively studied due to the possibility to choose between different cellulose types and to formulate networks chemically or physically, according to the adaptability requirements for each target application. The aim of this review is to showcase the cellulose structural versatility and to provide a summary of the principles during the formulation of CGs used for mechanosensing and mechanical energy scavenging, as well as their practical applications. Such an outlook of current challenges and overall prospects will serve as a stimulus for research on CG‐based mechanoreceptors in the future.

(Pod)wodne słuchanie i dryfująca antropologia hydrodźwięku

(Under)water Listening and a Drifting Anthropology of Hydrosound The aim of the article is to show the methodological and practical potential of combining anthropology of sound, wet ontology, and the oceanic ecology of the soundscape. I refer to this combination as the drifting anthropology of hydrosound. Taking advantage of the transdisciplinary nature of an anthropology of sound and presenting the specificity of underwater techno-mediated listening, I point to a shift towards less anthropocentric and inclusive understanding of human and environmental interactions. This inclusiveness is exceptionally clear in the practices of underwater listening. The article is divided into three parts. The first is an outline of the process of the emergence of anthropology of water and an introduction to the anthropology of sound. In the second part, I focus on the underwater listening processes. In the third, final one, I try to formulate the anthropology of hydrosound by referring to the wet ontology as well as multi- and interspecies approaches.

Acoustic data quality assessment tools and findings for ocean observing systems

Ocean Networks Canada (ONC) operates long time series, ocean observatories in the Pacific and Arctic. These include the large VENUS and NEPTUNE observatories, many small community based observatories and the Underwater Listening Station (ULS) for the Vancouver Fraser Port Authority. Passive acoustic monitoring systems are a component of all ONC observatories and passive acoustic data quality is therefore a concern. All the observing systems have multiple underwater electronics and sensor types, many of which can negatively impact the passive acoustic sensor data. Hydrophone sensitivity degradation due to time, water absorption, and biofouling need to be assessed to ensure accurate ambient noise measurements and accurate vessel underwater radiated noise level measurements. The performance and suitability of the hydrophones for specific areas also needs to be assessed so the acoustic analysts can be aware of the hydrophone induced data limitations. ONC has been examining the use of in situ calibration verifications, spectral probability density (SPD) plots, spectrograms, and wave data as tools to assess the passive acoustic data quality. The preliminary findings on the impact of all of the above acoustic error sources are presented.

Underwater sound energy from large terminal velocity raindrops as a function of drop volume, temperature, and salinity.

The principal underwater sound energy radiated by terminal velocity raindrops at sea is due to the bubble oscillations which occur for drops of diameter 0.8 to 1.1 mm (type I) and 2.2 to 4.6 mm (type II). In the absence of bubbles, between 1.1 and 2.2 mm, the impact sound radiation is significant. The type I bubbles radiate at frequencies close to 15 kHz, whereas type II bubbles radiate between 2 and 10 kHz, depending on drop diameter. Therefore type II bubbles, which are common in moderate to heavy rainfall, offer the opportunity to determine rainfall drop distribution and total rainfall rate by remote underwater listening. Type II bubbles radiate almost twice as much energy when the drop and surface temperatures differ by 10 °C. Type II bubbles radiate 45% as much energy in saline water (35 ppt) as in fresh water. The distinctive sound spectral shape for a particular diameter raindrop does not change appreciably with extreme differences of temperature (0 to 22 °C) or salinity (0 to 35 ppt). It is possible, therefore, to condense the data from hundreds of drops acquired in our laboratory into a single relation which gives the average energy radiated by a type II raindrop as a function of drop volume, temperature, and salinity. Using this relation, good agreement is found between measurements at sea and the predicted sound spectrum for a given drop-size distribution. Also, the total rainfall rate and drop-size distribution from sound spectra measured at sea (the inverse problem) are calculated. These early successes lay the groundwork for real-time measurements of total rainfall rate and drop-size distributions in moderate to heavy rainfalls by remote underwater listening. [Work supported by ONR.] a) Lt., USN.

Digital sound synthesis for underwater music perception

A piece of original electro‐acoustic music, Sonic Waters II, was created. Software “instruments” and “note lists,” descriptions of the behavior of those instruments in the musical time of a sequence, were specified for the cmusic synthesis program to produce, by frequency modulation, amplitude modulation, and localization and motion within a synthesized space, morphological transformations of several harp recordings. Means of (1) transduction of this wide‐band musical work (20 Hz to 16 kHz) for human listeners immersed in water and compensating for changes of such musically significant psychoacoustic cues as depth perception and relative amplitudes of overtones occasioned by the prominence of bone conduction in underwater listening were investigated. One pressure‐loaded diaphragm and four piezoelectric transducers were positioned to broadcast the computer‐processed sound. The wavelength of some bass notes exceeded the dimensions of the pool, limiting musically useful propagation of low frequencies due to cancellation and reinforcement of standing waves. [Work supported by the CME, System Development Foundation and the French government.]

An Investigation of Underwater Sound Localization in Shallow and Noisy Water

The ability of divers to discriminate the angular separation of two sound sources in the presence of high ambient noise in a reverberant environment was tested. In one experiment it was found that divers could not discriminate directionality with separations as large as 90° for low signal-to-noise ratios. However, when the signal to noise ratio was increased to about 19 dB, all four divers could discriminate a 30° angle with 100% accuracy. Two of the four divers could discriminate a 15° separation of sources. In a second experiment, a procedure was used in which the angular separation between sound sources could be continuously varied between about 35° and 1.4° in an “up and down” method. Six divers were tested but the data for one diver were uninterpretable. For the remaining five divers the underwater minimum audible angle for a 46-Hz band of noise centered at 1 kHz varied between 3.1° and 9.0° over all trials. Some suggestion that experience in underwater listening enhances localization skills appeared.

Calibration and Analysis of Underwater Earphones by Loudness-Balance Method

Recent experiments in underwater directional communication necessitated the use of earphones with uniform response characteristics. Two earphones from headset P-120-PQC-1 were calibrated underwater by the loudness-balance method at 50 dB above 1000-cps threshold sound-pressure level (SPL). A 25-dB range in response was observed in the frequency interval of 200–3000 cps, with principal resonance at 600 cps. Equalization was provided, after considering the 50-phon loudness contour, resulting in uniform response over the interval of 200–2500 cps. The experiment sheds some light on the role of tympanic versus bone-conduction modes in underwater listening, and suggests a receiver design with uniform frequency response and 40-times greater efficiency than the P-120-PQC-1.

Calibration and Analysis of Underwater Earphones by Loudness-Balance Method

Recent experiments in underwater directional communication necessitated the use of earphones with uniform response characteristics. Two earphones from headset P-120-PQC-1 were calibrated underwater by loudness-balance method at 50 dB above 1000-cps threshold SPL. A 35-dB range in response was observed in a frequency interval of 200–4000 cps, with principal resonance at 600 cps. Equalization was provided, after considering the role of the 50-phon loudness contour, resulting in uniform response over the interval of 200–2500 cps. The experiment sheds some light on the role of aural vs bone-conduction modes in underwater listening and suggests some approaches to improved underwater earphone and calibration methods. [Work supported, in part, by U. S. Navy Mine Defense Laboratory.]

THE ACOUSTICAL BEHAVIOR OF SOME FISHES IN THE BIMINI AREA

1. On the basis of observations and recordings at sea and in the laboratory, the acoustical behavior of 13 species of Bahamian fishes is described, and their sounds are defined. Twenty-six species producing no calls in the course of this study are specified.2. The most important sound-producers among fishes of the Bimini area are the squirrelfish, Holocentrus ascensionis, and the Nassau grouper, Epinephalus striatus. Their characteristic sounds may be anticipated when these species encounter a strange object at sea, and probably generally during the daytime along the edges of the Great Bahama Bank.3. A single observation has indicated that calling is a component of recognition behavior in the black angelfish, Pomacanthus arcuatus. The families Chaetodontidae and Holocentridae should be added to lists of fish families containing calling members.4. The usefulness of underwater listening in studying the distribution of some calling fishes has been demonstrated in the cases of the squirrelfish and Nassau grouper.