Acoustic Power Measurement and Thermal Bioeffect Evaluation of Therapeutic Langevin Transducers

We recently proposed an analytical design method of Langevin transducers for therapeutic ultrasound treatment by conducting parametric study to estimate the effect of compression force on resonance characteristics. In this study, experimental investigations were further performed under various electrical conditions to observe the acoustic power of the fully equipped transducer and to assess its heat-related bioeffect. Thermal index (TI) tests were carried out to examine temperature rise and thermal damage induced by the acoustic energy in fatty porcine tissue. Acoustic power emission, TI values, temperature characteristics, and depth/size of thermal ablation were measured as a function of transducer’s driving voltage. By exciting the transducer with 300 Vpp sinusoidal continuous waveform, for instance, the average power was 23.1 W and its corresponding TI was 4.1, less than the 6 specified by the Food and Drug Administration (FDA) guideline. The maximum temperature and the depth of the affected site were 74.5 °C and 19 mm, respectively. It is shown that thermal ablation is likely to be more affected by steep heat surge for a short duration rather than by slow temperature rise over time. Hence, the results demonstrate the capability of our ultrasonic transducer intended for therapeutic procedures by safely interrogating soft tissue and yet delivering enough energy to thermally stimulate the tissue in depth.

Acoustic MEMS Transducers: Look Ahead of the Bit and Geopressure Monitoring

This paper describes the design and implementation of Acoustic Micro Electro Mechanical Systems (hereinafter referred to asA-MEMS)working in fluid-coupling mode for HP/HT specifications relevant to downhole applications such as drilling, well and reservoir monitoring. Many cutting edges applications ofA-MEMS in Oil & Gas industry are envisaged. The current work refers to the case study of a "Look Ahead of the Bit"/geopressure monitoring technique (hereinafter referred to asPPM) developed by the authors. A–MEMS with magnetic shuttle transducers have been designed so that they are not affected by environmental pressure like piezoelectric devices commonly used in MWD commercial sonic tools, which are impaired by volumetric shrinking/expansion working principle. This performance is also achieved by embedding an environmental pressure compensator tuned in the whole working bandwidth to grant pressure balance even with oscillatory motion at sonic frequencies (up to 5 kHz). Transmitter acoustic power and receiver sensitivity have been optimized in a bandwidth between 500 and 3500 Hz. A couple of A–MEMS prototypes have been built and successfully tested by using an oil filled pressure vessel at downhole T–P conditions (200 °C, 700bar) and an ad-hoc measurement setup including force, displacement, temperature sensors, transmitter (TX) driver, receiver (RX) lock-in amplifier and anacquisition system. Moreover, modal analysis at typical drilling conditions has been carried out by Stewart platform. Shock up to 1000 g and random vibrations up to 12 g RMS in 5 ÷400 Hz bandwidth have been tested. A–MEMS performance have turned out to be consistent with theoretical model predictions andhave exhibited robustness to T P variations and applied structural stress. PPM method has been validated through a triaxial compression cell in a rock mechanics laboratory, implementing a lab scale scenario with a cap rock located above a permeable rock, undergoing all geopressures of interest. However, piezo transducers used in the experiment underwent a significant failure/damage rate along with performance degrading at pressure increasing. These observations confirmed and motivated the need for A-MEMS technology development in downhole applications.

Response Surface Analysis of DIB Nozzle Geometry on Acoustic Power Level using Central Composite Design of Experiment

The critical process parameters in manufacturing dry ice blasting nozzle geometry directly related to particle jet velocity. Many studies focused on its performance without considering the noise emission due to high operating pressure. This paper, a numerical simulation study was performed using Ansys Fluent to investigate the effect of nozzle geometry of single-hose dry ice blasting on the acoustic power level. The process of modelling the two-way mass momentum and energy exchange between two phases was successfully solved iteratively in the two-way mass momentum model and the energy exchange between the two phases. It was found that the value of noise emission reaches a maximum level when the shortest convergent angle of 20° with a minimal convergent length of 50 mm and a maximum length of 300 mm is introduced. Besides, the peak value of acoustic power level swell up to 146 dB occurs at a nozzle area ratio of 20 without influencing by convergent angle and extending the divergent length highly influencing noise reduction as less than 143.5 dB for a divergent length of 700 mm.

Intensity level as sustainable energy: Analysis of the conversion of energy stored on cicadas sound waves

In this study, the researchers measured cicadas' sound waves, considering that cicadas are mostly found in rural areas. The intensity level meter (AMTAST AMF003) was used with time variations (9:00 JST; 12:00 JST; and 15:00 JST). Measurements of air temperature differences (Krisbow Temperature Humidity Data Logger) were also carried out, and weather conditions were also considered in data collection using satellite data from Himawari, Japan. The interpretation results of intensity level's trend measured at 3:00 pm JST were decreased concerning the changes in days. Meanwhile, the measurement at 09:00 am and 12:00 pm JST did not show a decrement concerning the changes in days (31 days in total). These results show that temperature changes (towards autumn) can affect the intensity level of sound waves. In addition, slightly different intensity levels can affect large changes in acoustic power or the produced sound.

A proper framework for studying noise from jets with non-compact sources

A quantitative assessment of the acoustic source field produced by a laboratory-scale heated jet with a gas dynamic Mach number of 1.55 and an acoustic Mach number of 2.41 is performed using arrays of microphones that are traversed across the axial and radial plane of the jet's acoustic field. The nozzle contour comprises a method of characteristics shape so that shock-related noise is minimal and the dominant sound production mechanism is from Mach waves. The spatial topography of the overall sound pressure level is shown to be dominated by a distinct lobe residing on the principal acoustic emission path, which is expected from flows of this kind with supersonic convective acoustic Mach numbers. The sound field is then analysed on a per-frequency basis in order to identify the location, strength, convection velocity and propagation angle of the various axially distributed noise sources. The analysis reveals a collection of unique data-informed polar patterns of the sound intensity for each frequency. It is shown how these polar patterns can be propagated to any point in the far field with extreme accuracy using the inverse square law. Doing so allows one to gauge the kinds of errors that are encountered using a nozzle-centred source to calculate sound pressure spectrum levels and acoustic power. It is proposed that the measurement strategy described here be used for situations where measurements are being used to compare different facilities, for extrapolating measurements to different geometric scales, for model validation or for developing noise control strategies.

Ultrasound Mediated Wireless Power Transfer Technology

Wireless energy transfer (WET) is the transmission of electric power without any physical connections such as wires. Currently, inductive coupling mediated by electromagnetic (EM) waves is the most common method of WET and is widely used to charge portable devices such as smartphones, Bluetooth earphones, electric shavers, and visual prostheses. However, its application is still limited due to a number of issues including low efficiency, short charging distance, heating problem, and limited choice of transmission medium. Due to these issues, EM-based WET cannot be applied to implantable medical devices, marine cable operation sensors, and electronic devices with electromagnetic interference shielding. Recently, as an alternative to EM-based WET, acoustic energy transfer mediated by sound waves becomes more attractive. Ultrasound offers advantages for transmission in dense media such as liquids or solids and is regardless of electromagnetic shielding. In this review, we investigate recent progress in acoustic power transfer technology in terms of acoustic energy conversion mechanism and provide the future research direction of acoustic power transfer technology.