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Experimental investigation on the hydro-acoustic characteristics of tandem cylinders
Published in Selma Ergin, C. Guedes Soares, Sustainable Development and Innovations in Marine Technologies, 2022
The diameter of the cylinders used in the experiments is 20 mm. The cylinders are made of aluminum and covered with anodized coating to both protect against corrosive effects and minimize surface roughness.Fixing plates have threaded slots which uses cylinders to tightly place. The plates are fixed adjacent to the side walls of the duct. Any vibration on the cylinders and plates is prevented by using special fixing apparatus. Hydroacoustic measurements are recorded by using Bruel&Kjær (B&K) 8104 hydrophone. The sensitivity of the hydrophone is -205 dB per 1V/μPa. The frequency range of the hydrophone is from 0.1Hz to 120 kHz. The hydrophone is placed in a “measuring assembly”. Details about the fixing plate and the measuring assembly are presented in Figure 2.
Recent Advances in Piezoelectric Ceramics
Published in Lionel M. Levinson, Electronic Ceramics, 2020
Robert C. Pohanka, Paul L. Smith
A hydrophone is an underwater microphone or transducer used to detect underwater sound. The sensitivity of a hydrophone is determined by the voltage produced by a hydrostatic pressure wave. The hydrostatic voltage coefficient relates the electric field appearing across a transducer to the applied hydrostatic stress and is therefore a useful parameter for evaluating piezoelectric materials for use in hydrophones. Another piezoelectric coefficient frequently used is the hydrostatic strain coefficient dh, which describes the polarization resulting from hydrostatic stress. The gh coefficient is related to the dh coefficient by the relation gh = dh/ε0K, where ε0 is the permittivity of free space and K is the relative permittivity of the material.
Fluid-sound
Published in Liz Roberts, Katherine Phillips, Water, Creativity and Meaning, 2018
Hydrophones are underwater microphones that detect sub-surface vibrations and sound waves. They allow the recordist to hear underwater soundscapes that would otherwise be inaudible. Hydrophone technologies were developed through military use in the early twentieth century, largely in a marine setting, used as a complement for sonar and in so doing facilitating early recordings of whale song (Helmreich 2015). The resulting insights hydrophones offered into both the sounds of underwater life and the sonic characteristics of water have informed the work of artists such as John Cage, Max Neuhaus, David Dunn, Peter Cusack and Jana Winderen. In particular, Dunn’s (2016, 28) environmental art practice figures hydrophone listening as means of accessing hidden more-than-human lifeworlds, suggesting that such practices can ‘facilitate an increase in our collective environmental sensitivity and discovery of unknown natural and human made phenomena’.5
The Velocity of Underwater Ultrasound at Different Temperatures
Published in IETE Journal of Research, 2023
Measurement of sound waves in water has been performed in various situations such as the characterization of medical transducers, development and maintenance of equipment in the industry, and sound measurement of organisms. Since the sound field is non-stationary in many cases, there is a demand for the measurement of sound fields whose environment changes with time. Underwater sound measurement is usually performed using a hydrophone [1]. Various things and media can be evaluated using ultrasound. It is particularly used when electromagnetic radiation cannot travel through it since it is opaque. Ultrasonic waves can be excited using some transducers and then detected after traveling entirely through or partially through the object being evaluated. The ultrasonic wave’s attenuation is determined from the measured reduction in wave amplitude, and its velocity is calculated from the measured propagation delay. These characteristics differ from one material to another and are also influenced by outside factors like temperature [2].
A review of NDE techniques for hydrogels
Published in Nondestructive Testing and Evaluation, 2023
Sasidhar Potukuchi, Viswanath Chinthapenta, Gangadharan Raju
In the field of NDE techniques, focus is required on developing novel testing protocols like the combined use of multiple techniques and the deployment of sensors from other fields. Respective examples are as follows: An acoustic sensor could give greater insights into the failure mechanisms of a material due to its higher sensitivity which might not be seen in a force-vs-displacement signal. Hydrophones were traditionally used for acoustic tracking underwater but are now being deployed for needle tracking and force estimations. Another pertinent example is the use of VT combined with passive thermography for characterising the gel mechanical behaviour. However, vibration-based evaluation of mechanical properties is not as common in gels as in composite materials. Such studies open opportunities to develop creative and out-of-the-box methodologies to analyse the behaviour of gels from nano- to macro-scales.
Leak detection in water distribution pipes using singular spectrum analysis
Published in Urban Water Journal, 2018
Roya Cody, Jinane Harmouche, Sriram Narasimhan
Experiments and data acquisition were conducted under four scenarios: (1) ambient, which means there is no leak and the valve is closed; (2) under leak condition, where a leak is present and the valve is closed; (3) valve, where the network is leak-free and the valve is open, (4) valve and leak, where a leak is present and the valve is open. For each scenario, the acoustic signals were acquired at different times over a month with a sampling frequency of 1.35 kHz. The data was collected for up to two minutes in 10 to 30 second intervals at different times throughout a given day and this data collection program spread over one month. This was to ensure that most of the variations in the data were captured and to minimize the effects of overfitting to specific system conditions. Since the pipes are connected directly to the building water distribution system, the experimental data also reflects the supply and demand patterns of the city network. Data was collected using a custom hydrophone and data acquisition system. The sensitivity of the hydrophone used in this study is −193 dB re 1V/μPa with an added amplification of 20 dB prior to data-acquisition and a sample of the collected acoustic pressure time history from the hydrophone is shown in Figure 2.