Hasil untuk "Acoustics. Sound"

Lucian Zigoneanu, B. Popa, S. Cummer

B. Pijanowski, A. Farina, S. Gage et al.

S. Rothberg, Allen, P. Castellini et al.

Tyler W. Hughes, Ian A. D. Williamson, M. Minkov et al.

Analog machine learning computations are performed passively by propagating light and sound waves through programmed materials. Analog machine learning hardware platforms promise to be faster and more energy efficient than their digital counterparts. Wave physics, as found in acoustics and optics, is a natural candidate for building analog processors for time-varying signals. Here, we identify a mapping between the dynamics of wave physics and the computation in recurrent neural networks. This mapping indicates that physical wave systems can be trained to learn complex features in temporal data, using standard training techniques for neural networks. As a demonstration, we show that an inverse-designed inhomogeneous medium can perform vowel classification on raw audio signals as their waveforms scatter and propagate through it, achieving performance comparable to a standard digital implementation of a recurrent neural network. These findings pave the way for a new class of analog machine learning platforms, capable of fast and efficient processing of information in its native domain.

David Santos-Domínguez, S. Torres-Guijarro, Antonio Cardenal-López et al.

Andrew Luo, Yilun Du, M. Tarr et al.

Our environment is filled with rich and dynamic acoustic information. When we walk into a cathedral, the reverberations as much as appearance inform us of the sanctuary's wide open space. Similarly, as an object moves around us, we expect the sound emitted to also exhibit this movement. While recent advances in learned implicit functions have led to increasingly higher quality representations of the visual world, there have not been commensurate advances in learning spatial auditory representations. To address this gap, we introduce Neural Acoustic Fields (NAFs), an implicit representation that captures how sounds propagate in a physical scene. By modeling acoustic propagation in a scene as a linear time-invariant system, NAFs learn to continuously map all emitter and listener location pairs to a neural impulse response function that can then be applied to arbitrary sounds. We demonstrate that the continuous nature of NAFs enables us to render spatial acoustics for a listener at an arbitrary location, and can predict sound propagation at novel locations. We further show that the representation learned by NAFs can help improve visual learning with sparse views. Finally, we show that a representation informative of scene structure emerges during the learning of NAFs.

Yong Deng, Adrian Paskert, Zhiyuan Zhang et al.

As a next-generation toolkit, microrobots can transform a wide range of fields, including micromanufacturing, electronics, microfluidics, tissue engineering, and medicine. While still in their infancy, acoustically actuated microrobots are becoming increasingly attractive. However, the interaction of acoustics with microstructure geometry is poorly understood, and its study is necessary for developing next-generation acoustically powered microrobots. We present an acoustically driven helical microrobot with a length of 350 μm and a diameter of 100 μm that is capable of locomotion using a fin-like double-helix microstructure. This microrobot responds to sound stimuli at ~12 to 19 kHz and mimics the spiral motion of natural microswimmers such as spirochetes. The asymmetric double helix interacts with the incident acoustic field, inducing a propulsion torque that causes the microrobot to rotate around its long axis. Moreover, our microrobot has the unique feature of its directionality being switchable by simply tuning the acoustic frequency. We demonstrate this locomotion in 2D and 3D artificial vasculatures using a single sound source.

D. Huber, Robert E. Runstein

Introduction Sound and Hearing Studio Acoustics and Design Microphones - Design and Application Analog Tape Recorder Digital Audio Technology MIDI Multimedia Synchronization Amplifiers Audio Production Console Signal Processors Noise Reduction Monitoring Product Manufacture Studio session procedures Yesterday, Today and Tomorrow

Harshith K. Adepu, Chelsea M. O'Donnell, Justin Y. Kim et al.

Ultrasonic inspection plays a critical role in nondestructive material characterization. Contact-based methods have been used in industry and field inspections for decades due to their portability. Although immersion testing provides improved spatial resolution, its adoption has been limited to commercial or research facilities due to its cost and footprint. Here, we present a frugal design for a custom immersion system based on a repurposed three-dimensional printer and show that ultrasonic wave speed measurements collected with the custom system and a commercial system are in statistical agreement. This work enables broader adoption of immersion ultrasonics for industry, education, and workforce development.

Zhijin Shang, Hongpeng Wu, Gang Wang et al.

Mouhamad Haidar Lakkis, Jennifer Watchi, Rasa Jamshidi et al.

This paper addresses a theoretical control approach and its corresponding experimental validation for low-frequency active damping and isolation of a six-degree-of-freedom platform using high-resolution inertial sensors. Six vacuum-operating inertial sensors are placed on top of the platform to actively control it. Three of them measure displacements in horizontal directions and three in vertical directions. The resonance frequencies of the vertical and horizontal sensors range between 0.3 and 0.7 Hz with a resolution of 2 × 1 0 − 13 m / Hz at 1 Hz for both types of sensors. Sensor signals are fed back into six voice coil actuators (three horizontal and three vertical) mounted below the platform. Actuators and sensors are placed in a quasi-collocated architecture facilitating the controllability of the plant. The platform (with resonance frequencies ranging between 1 and 10 Hz) is actively isolated by up to two orders of magnitude between 0.1 and 10 Hz, yielding a final overall displacement RMS value below 100 nm at its center of mass from 0.3 Hz onward.

Chih-Hsien Li, Wei-Hao Chao, Ping-Ching Wu et al.

Biofilms constitute a major challenge in treating implant-associated and chronic infections due to their structural resilience and drug resistance, particularly as implant demand rises due to aging populations. Conventional methods are often invasive, complex, and costly, while focused ultrasound (FUS) poses risks related to biocompatibility and tissue damage. Distinguished by its helical phase structure and rotational energy distribution, focused acoustic vortex (FAV) theoretically generates stronger rotational forces and acoustic streaming than FUS under identical acoustic conditions. This study investigates the feasibility of FAV technique for biofilm removal. Biofilms in vitro model were established using Escherichia coli, and a 2-MHz custom-built ultrasound transducer was employed to generate either FAV or FUS. Results indicated that FAV activation generated a centripetal vortical flow with rapid rotation, which was adjustable via acoustic pressure and duty cycle. Conversely, FUS generated solely outward acoustic streaming, exhibiting a flow velocity 43.6 % lower than that of FAV. At 1.75 MPa, implementing a 10 % duty cycle and a 180 s treatment, FAV removed 97 % of the biofilm, whereas FUS removed only 7 %. To achieve a comparable removal rate (95.8 %), FUS required 4 MPa for 10 minutes. Streaming velocity (R2 = 0.99) exhibited a strong correlation with biofilm removal, while inertial cavitation (R2 = 0.19) exhibited a weak correlation; thus, the former was identified as the primary contributing mechanism. Importantly, FAV treatment resulted in minimal thermal elevation (<5 °C) and no significant reduction in cell viability, demonstrating its biosafety under the applied acoustic parameters. Synergistic tests with antibiotics further suppressed biofilm regrowth for up to 72 h, reducing bacterial concentration by 91 %. Future work will focus on in vivo biofilm models and assessing the safety and efficacy of combined treatments to advance clinical applications.

Xiaoyan Zhu, Tin Oberman, F. Aletta

The interdisciplinary study of acoustics/sound and heritage occurs in different countries and cultures, but there is no uniform consensus on the terminology and definitions of the field. This study aims to explore the definition of acoustical heritage. The study used structured interviews with experts from different cultures and different disciplines and analyzed the interview data in detail through thematic analysis. The five themes are: different terminology, subjects in acoustical heritage, possible categories of acoustical heritage, value of acoustical heritage, and challenges of acoustical heritage preservation. Based on individual definitions of acoustical heritage proposed by experts and through detailed analysis and discussion, this paper proposes a multidimensional definition of acoustical heritage.

Tara Khursheed, Anees Ahmed Khalil, Muhammad Nadeem Akhtar et al.

Centella asiatica has been known for its significant medicinal properties due to abundance of bioactive constituents like triterpenoids and flavonoids. Nevertheless, an appropriate solvent system and extraction technique is still lacking to ensure optimized extraction of bioactive constituents present in C. asiatica. Recently, scientists are more focused towards application of green sustainable extraction techniques for the valuable components from plant matrix owing to their eco-friendly and safe nature. Among these, ultrasonication (US) is known as a valuable strategy for separation of bioactive components from medicinal plants. Hence, current research was performed to observe the effect of ultrasonication in the presence of five different solvents (Water, Hexane, Methanol, Chloroform, and Ethyl acetate) on total phenolic contents (TPC), total flavonoid contents (TFC), antioxidant properties (DPPH, ABTS, Nitric oxide radical activity, and Superoxide anion assay), and four major triterpenoid contents in C. asiatica leaves. Herein, ultrasound assisted methanolic extract (UAME) possessed maximum amount of TPC (129.54 mg GAE/g), TFC (308.31 mg QE/g), and antioxidant properties (DPPH: 82.21 % &amp; FRAP: 45.98 µmol TE/g) followed by ultrasound-assisted Water extract (UAWE), ultrasound-assisted ethyl acetate extract (UAEAE), ultrasound-assisted n-hexane extract (UAHE), and ultrasound-assisted chloroform extract (UACE), respectively. Moreover, the superoxide radical and nitric oxide assays depicted a similar trend, revealing the highest percent inhibition for UAME (SO: 83.47 % &amp; NO: 66.76 %) however, the lowest inhibition was displayed by UACE (63.22 % &amp; 50.21 %), respectively. Highest content of major terpenoids were found in UAME of C. asiatica leaves as madecassoside (8.21 mg/g) followed by asiaticoside (7.82 mg/g), madecassic acid (4.44 mg/g), and asiatic acid (3.38 mg/g). Ultrasound-assisted extraction technique can be an efficient extraction method for bioactive compounds present in C. asiatica. However, ultrasonication along with methanol as an extraction solvent can surely enhance the extraction of valuable constituents. The results of this study provide an insight into major terpenoids, and antioxidants present in extracts of C. asiatica, implicating its use in ancient medicine systems and future drug development.

Sun Qi, Zhang Kaiyin

Resonance of multi-degree-of-freedom system or structure is a basic and important concept in structural vibration theory, but it lacks a complete and rigorous definition. In order to establish an accurate concept of structural resonance, based on the concept of single-degree-of-freedom system resonance and modal orthogonality, this paper discusses the necessary conditions of system resonance by analyzing the displacement response of multi-degree-of-freedom vibration system, that is, while ensuring that the vibration frequency of the system (a certain natural frequency) is equal to the excitation frequency, its displacement response should also present the corresponding modal shape. An example of simply supported beam is used to illustrate its rationality. At the same time, the theoretical method of pure modal resonance of multi-degree-of-freedom system is given by rational allocation of excitation force. The pure modal resonance of multi-degree-of-freedom system or structure can be realized, which can be used to accurately identify the modal parameters of the structure. It is of great theoretical significance and engineering application value to discriminate the concept of multi-degree-of-freedom system or structure resonance.

Chia-Wei Lin, Jeng-Yi Shieh, Po-Hsiang Tsui et al.

We investigated whether the upper limb muscle stiffness quantified by the acoustic radiation force impulse shear wave elastography (ARFI/SWE) is a potential biomarker for age-related muscle alteration and functional decline in patients with Duchenne muscular dystrophy (DMD). 37 patients with DMD and 30 typically developing controls (TDC) were grouped by age (3–8, 9–11, and 12–18 years). ARFI/SWE measured the biceps and deltoid muscle's shear wave velocities (SWVs). Performance of Upper Limb Module (PUL 1.2 module) assessed muscle function in DMD patients. Mann Whitney test compared muscle SWVs between DMD and TDC, stratified by three age groups. We used analysis of variance with Bonferroni correction to compare muscle SWVs between DMD and TDC and correlated muscle SWVs with PUL results in the DMD group. Results showed that the SWVs of biceps differentiated DMD patients from TDC across age groups. Younger DMD patients (3–8 years) exhibited higher SWVs (p = 0.013), but older DMD patients (12–18 years) showed lower SWVS (p = 0.028) than same-aged TDC. DMD patients had decreasing biceps SWVs with age (p < 0.001), with no such age effect in TDC. The SWVs of deltoid and biceps positively correlated with PUL scores (r = 0.527 ∼ 0.897, P < 0.05) and negatively correlated with PUL timed measures (r = −0.425 ∼ −0.542, P < 0.05) in DMD patients. Our findings suggest that ARFI/SWE quantifying the SWVs in upper limb muscle could be a potential biomarker to differentiate DMD from TDC across ages and that DMD patients showed age-related muscle alteration and limb functional decline.

Linmin Li, Yabiao Niu, Guolai Wei et al.

We have employed the large eddy simulation (LES) approach to investigate the cavitation noise characteristics of an unsteady cavitating flow around a NACA66 (National Advisory Committee for Aeronautics) hydrofoil by employing an Eulerian-Lagrangian based multiscale cavitation model. A volume of fluid (VOF) method simulates the large cavity, whereas a Lagrangian discrete bubble model (DBM) tracks the small bubbles. Meanwhile, noise is determined using the Ffowcs Williams-Hawkings equation (FW-H). Eulerian-Lagrangian analysis has shown that, in comparison to VOF, it is more effective in revealing microscopic characteristics of unsteady cavitating flows, including microscale bubbles, that are unresolvable around the cloud cavity, and their impact on the flow field. It is also evident that its evolution of cavitation features on the hydrofoil is more consistent with the experimental observations. The frequency of the maximum sound pressure level corresponds to the frequency of the main cavity shedding for the noise characteristics. Using the Eulerian-Lagrangian method to predict the noise signal, results show that the cavitation noise, generated by discrete bubbles due to their collapse, is mainly composed of high-frequency signals. In addition, the frequency of cavitation noise induced by discrete microbubbles is around 10 kHz. A typical characteristic of cavitation noise, including two intense pulses during the collapsing of the cloud cavity, is described, as well as the mechanisms that underlie these phenomena. The findings of this work provide for a fundamental understanding of cavitation and serve as a valuable reference for the design and intensification of hydrodynamic cavitation reactors.

A. Yu. Klokov, N. Yu. Frolov, A.I. Sharkov et al.

Acoustic properties of buried graphitized layers in diamond formed by ion implantation followed by annealing were studied using the picosecond ultrasonic technique with spatial resolution. Two methods of elastic pulse generation were used: heating an aluminum film deposited on a diamond sample by femtosecond laser pulses and direct illumination of the graphitized layers by these pulses. We applied a multilayered model of the acousto-optical response to fit experimental results and estimate the distribution of the acoustical parameters (wave resistance, viscoelastic damping, and longitudinal sound speed) of the structures under study in depth. It was found that unique sets of spectral lines are present in the Fourier spectra of measured responses in regions with different internal structures. Mapping of the Fourier spectra made it possible to visualize regions with different internal structures. The combined use of depth profiling and mapping can serve as a tool for hypersound tomography.