Acoustic Technology Research Articles

Sound absorbing properties of spiral metasurfaces inspired by micro-perforated plates

As a kind of classical low-frequency sound-absorbing material, the microperforated plate (MPP) has been widely used. Here, we inspired by the sound absorption mechanism of the MPP, a spiral metasurface (SM) is designed and the analytical solution of acoustic impedance and sound absorption coefficient are obtained. The relationship between the sound absorption properties of the MPP and the SM with their own structures is systematically studied, and the analytical solutions are used to optimise the structure. It is concluded that the MPP and the SM of the same thickness achieve effective absorption in the frequency range between 390-900 Hz and 1920-4266 Hz, with a total thickness less than 1/6 of the wavelength. Meanwhile, the numerical calculation shows that the MPP and SM can match well with the background medium in the effective rang. Our study provides new insights into the design methods of sound-absorbing materials and is potentially suitable for many acoustic engineering applications.

Damage detection, quantification, and localization for resonant metamaterials using physics-based and data-driven methods

Resonant metamaterials have attracted significant research interest in mechanical and acoustic engineering with applications in the fields of sound and vibration control thanks to their integrated tuned mass dampers. One prevailing issue regarding industrial application of such structures is the high probability of local damage for their resonating parts. Accurate and efficient health state estimation methods for resonant metamaterials are therefore urgently required. In particular, the quantification and localization of damaged resonators represent key pieces of information for the operator of a structural asset. This work presents for the first time an investigation into quantifying and identifying damaged oscillators in a resonant metamaterial based on the measured frequency response function (FRF) data. Both data-driven and physics-based methods are implemented and corresponding results are exhibited. Manufacturing-induced structural uncertainty is quantified through physical measurements and taken into account in this work. It is demonstrated that such uncertainty may have a rather significant impact on the response of 3D printed resonant metamaterials, leading to difficulties vis-a-vis damage quantification. The proposed theoretical developments are able to properly account for such uncertainties, providing probabilistic estimation indices for the existing damage level and location. Both simulated and experimental case studies are presented to validate the two proposed methodologies and comparisons are also exhibited and discussed.

A Study on the Application of Advanced Acoustic Information Technology for the Completion of Autonomous Driving Vehicles

Since Autonomous Driving Vehicles are directly related to human life, it is necessary to put the utmost effort into safe driving to the point of being almost perfect. Also, for the best safety, any technology should be borrowed, tested, and applied. In this paper, the method of applying sound information to the Autonomous Driving Vehicles research presented last time will be emphasized and specified. Since the sound information to be applied to Autonomous Driving Vehicles is vast, it must be made into big data and must be used in various and precise ways, so it must be made into IOT based on AI. Sound Information Technology must be equipped with technology that can perfectly judge changing conditions such as time, season, and weather depending on the location. Acoustic Information Technology can be largely divided into ES(Environmental Sounds) and TS(Things Sounds). Environmental Sound is to detect the conditions of the surrounding environment including the road or the ground on which the vehicle is traveling with sound information. Things Sounds is to detect fixed or moving Things around the vehicle with sound information. In the future, it is expected that various methods of Sound Information Technology will be able to contribute greatly to the achievement of the era of Free Driving vehicles, which is the completion stage of Autonomous Driving Vehicles.

Effect of Audio Control Technology on Lettuce Growth

The excessive use of pesticides and fertilizers reduces the quality of crops, harms human health, and causes environmental pollution, thus hindering the sustainable development of agriculture. In the process of realizing ecological agricultural production, audio control technology has increasingly become an area of concern. As a physical agricultural technology, it has become a combination of music acoustics and agricultural science. However, the research on the ecological role and function of audio control technology is still relatively lacking. In view of this, the authors studied the effects of audio control technology (specific frequency sound wave and different types of music) on the growth of lettuce, and showed that the specific frequency sound wave treatment produced by the plant acoustic frequency technology generator significantly increased the growth of lettuce compared with the condition of silent environment processing. Treatments of different types of music (electronic music, rock music, and classical music) promoted lettuce growth, especially the significant increase in the output of edible parts under the influence of electronic music. The research results further showed that the specific frequency sound wave treatment produced by the plant acoustic frequency technology generator enhanced the chlorophyll content of lettuce leaves (1.98 ± 0.15 mg/g), thus promoting photosynthesis. Different types of music had different effects on the photosynthesis of lettuce leaves; electronic music treatment increased the chlorophyll content of lettuce (1.48 ± 0.07 mg/g), and had the greatest impact.

Research on the Development and Application of Acoustic Testing Technology

Taking the commonly used acoustic detection technology as the research object, the working principle of different types of acoustic detection technology and the application of adverse geological forecasting and nondestructive testing in the geotechnical field are described, and the advantages and disadvantages of different types of acoustic detection technology are pointed out through the discussion of the development of acoustic detection technology.

LOWNOISEPAD: Low-cost noise control by optimized rail pad: Feasibility study on the use of rail pad as noise mitigation measure

When aiming to minimize track noise, there is a significant conflict of aims that must be considered. Tracks with stiff rail pads are generally less noisy than ones with soft rail pads. Stiff rail pads, however, can decrease the long-term quality of the track. In order to achieve an optimum, beside stiffness also rail pad damping at relevant frequencies must be considered. The International Union of Railways (UIC) works with its members to better understand the noise-generation and rail pad effects. The LOWNOISEPAD project brings together the European railway community in an effort to find an optimal rail pad for both noise and track quality issues and for the different situations encountered in 12 European railway networks. Besides acoustic rail roughness, the stiffness and damping properties of rail fastening systems such as rail pads have a considerable influence on rail noise. In practice, rail pad design is always a compromise between track engineers' demand for flexibility and acoustic engineers' expectations for sufficiently high Track Decay Rate. The paper describes the measurements undertaken in the project, shows first conclusions as well as a software tool that allows determining noise levels after installing rail pads with given stiffness and damping properties.

Design, material, function, and fabrication of metamaterials

Metamaterials are engineered materials with unusual, unique properties and advanced functionalities that are a direct consequence of their microarchitecture. While initial properties and functionalities were limited to optics and electromagnetism, many novel categories of metamaterials that have applications in many different areas of research and practice, including acoustic, mechanics, biomaterials, and thermal engineering, have appeared in the last decade. This editorial serves as a prelude to the special issue with the same title that presents a number of selected studies in these directions. In particular, we review some of the most important developments in the design and fabrication of metamaterials with an emphasis on the more recent categories. We also suggest some directions for future research.

Evaluation of double acoustic tagging techniques to track American shad Alosa sapidissima movements at multiple spatial scales

Enhancements to acoustic telemetry technology now allow for tracking aquatic animal movements at multiple spatial and temporal scales. While large acoustic arrays allow for broad-scale tracking of movement and migrations at scales of thousands of km across multiple years, more focused smaller arrays offer the potential to quantify fine-scale movement across shorter time frames. Investigators seeking to quantify movement at multiple scales may require a double-tagging approach if their telemetry systems and tag capabilities are different (e.g., 69 kHz for broad-scale, and 307 kHz for sub-meter fine-scale). We tested multiple double-tagging approaches (InnovaSea-Vemco V9 and HTI-495LY tags) for American shad Alosa sapidissima during three individual tank survival experiments including: 1) two free-floating acoustic tags and a dart tag, 2) two acoustic tags attached to one another and a dart tag, and 3) two acoustic tags attached to one another with no dart tag and revised handling and tagging techniques to reduce stress. In each experiment, we used a mixed effects Cox’s proportional hazard model to test for differences in relative survival between groups (double acoustic tagged and control fish). At the completion of each experiment, all fish were X-rayed to evaluate tag placement in the body cavity. During the first experiment, American shad that received two free-floating tags and a dart tag had significantly lower relative survival compared to control fish after three weeks. The second experiment with treatment fish receiving two attached tags and a dart tag still had lower survival compared to control fish, but the magnitude of survival differences between treatment and control was lower compared to experiment one. In the third experiment, when two attached tags were used, dart tags were eliminated, and changes to fish handling and tagging techniques were implemented (new tagging apparatus, addition of lubricant, and different fish orientation) survival was equal among treatment and control fish. X-ray images showed distinct differences in post-mortem tag positioning between the first experiment (misaligned tags) compared to the second and third experiments (tags horizontally aligned within intestinal tract). American shad are generally difficult to study experimentally and sensitive to collection, handling, and surgical implantation. Our study showed strong evidence that attaching two acoustic tags to one another to create a single, larger tag improved survival and reduced internal tag misalignment. Fine- and broad-scale acoustic telemetry studies can be achieved with aquatic animals, but care must be taken with all species, and particularly those susceptible to handing stress to minimize tagging effects (e.g., mortality, altered movement behaviors, and tag burden).

Acoustic Model for Leak Detection of Water Supply Pipeline

The leak detection of water supply pipelines is significant for the protection of water resources. Acoustic detection is a common method used to investigate water supply pipeline leaks. Although some acoustic methods for the leak detection of the water supply pipeline have been developed experimentally, the theoretical investigation of said acoustic methods is still limited. Compared with aeroacoustics, the development of quantitative jet acoustic theory towards flow field calculations of liquid pipeline leak has not been reported, and the characteristics of the liquid flow field cannot be quantitatively transformed into the acoustic model. In this paper, the liquid pipeline leak is combined with piston acoustics, and the acoustic model for the leak detection of the water supply pipeline is quantitatively studied for the first time. The acoustic pressure value can be directly calculated using pipe and liquid parameters, and the validity of the model can be verified experimentally. Based on theoretical and experimental investigations, it is found that the leak sound pressure increases significantly with increasing pipeline pressure and decreases with increasing detection distance. The material composition of the pipes has little influence on the leak sound pressure. The theoretical values based on the proposed acoustic model and the experimental values agree well, where the maximum difference between them is 8.5% and the average difference is 2.6%. This study presents a foundation for the development of acoustic leak detection technology of the liquid pipeline.

Research on modulation recognition of underwater acoustic communication signal based on deep learning

Marine information technology plays a important role in the development of marine resources development, marine climate early warning, and other industries. Underwater acoustic communication technology can help us better access marine information. The performance of the underwater acoustic signal modulation recognition algorithm depends on the accuracy of feature extraction. however, due to excessive underwater noise, many traditional algorithms can not recognize features well. For this reason, this paper proposes a modulation recognition network for aquatic communication signals based on deep learning. ResNet can capture the characteristics of deep features and combines ResNet with a modulation recognition network. Finally, the experiment proves the effectiveness of this method.

On the Physical Layer Security Performance Over RIS-Aided Dual-Hop RF-UOWC Mixed Network

Since security has been one of the crucial issues for high-yield communications such as 5G and 6G, researchers continuously come up with newer techniques to enhance the security and performance of these progressive wireless communications. Reconfigurable intelligent surface (RIS) is one of those techniques that artificially rearrange and optimize the propagation environment of electromagnetic waves to improve both spectrum and energy efficiency of wireless networks. Besides, in underwater communication, underwater optical wireless communication (UOWC) is a better alternative/replacement for conventional acoustic and radio frequency (RF) technologies. Hence, mixed RIS-aided RF-UOWC can be treated as a promising technology for future wireless networks. This work focuses on the secrecy performance of mixed dual-hop RIS-aided RF-UOWC networks under the intercepting effort of a probable eavesdropper. The RF link operates under generalized Gamma fading distribution; likewise, the UOWC link experiences the mixture exponential generalized Gamma distribution. The secrecy analysis subsumes the derivations of closed-form expressions for average secrecy capacity, exact and lower bound of secrecy outage probability, strictly positive secrecy capacity, and effective secrecy throughput, all in terms of Meijer's <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$G$</tex-math></inline-formula> functions. Capitalizing on these derivations, the effects of heterodyne and intensity modulation/direct detection systems, underwater turbulence resulting from air bubble levels, temperature gradients, and salinity gradients, are measured. Unlike conventional models that merely deal with thermally uniform scenarios, this proposed model is likely to be unique in terms of dealing with secrecy analysis of a temperature gradient RIS-aided RF-UOWC network. Lastly, the derivations are validated via Monte-Carlo simulations.

Acoustic Emission Characteristics and Damage Evolution Analysis of Sandstone under Three-Point Bending Test

In order to study the prevention of roadway roof bending, sinking, and breaking and the prevention of dynamic disasters such as the appearance of rock bursts, three-point bending experiments of sandstone under different spans were carried out. By using stress loading system and acoustic emission technology, the acoustic emission characteristic parameters of the sandstone fracture process were analyzed, the precursory information of rock bending fracture was explored, and the evolution law of sandstone damage based on acoustic emission characteristics was obtained. The results showed that according to the variation of acoustic emission ringing count, the load-time curve was divided into four typical stages: the first stage showed an overall increasing trend; the second stage showed an obvious increasing trend; the third stage showed obvious accelerated growth and the acoustic emission ringing count reached the maximum at the moment of rupture. In the fourth stage, the amplitude and frequency of the ringing count are large and high. With the increase in span, the cumulative ringing counts of AE decreased, and the rate of change gradually decreased. The fracture process of three-point bending sandstone can reflect the precursor information of rock fracture from time domain, frequency domain, and R value (ratio of cumulative acoustic emission ringing count to cumulative energy count). In time domain, the evolution characteristics of AE cumulative ringing count stage II can be used to predict the three-point bending fracture of sandstone. The peak frequency shows a linear increase after a spike and then an accelerated increase to a rupture, and the boundary point between the spike and the linear and nonlinear can be obtained. The decrease in R value can indicate that the main crack is growing in the specimen. According to the damage rate, the characteristics of the damage variables can be divided into five stages: stationary and low, gradually increasing, gradually decreasing, main crack coalescence, and complete fracture. With the increase in span, the fracture damage shows a decreasing trend. The residual damage fluctuates between 0.38 and 0.40 due to the difference in crack propagation trajectory. It has theoretical research value for revealing the internal mechanism of rock bending and fracture and has engineering guiding significance for mine pressure and rock strata control and dynamic disaster prevention.

Resolving clashes between net-zero energy and acoustics engineering specifications, to enhance low-carbon building performance, regulatory compliance and future skills. Laws and standards comparison between Italy and UK

Under the CNR (Italy) and RSE (Scotland) joint scientific cooperation agreement, the present project deals with the development and enhancing understanding of the technical clashes and engineering solutions required to deliver net-zero outcomes across diverse construction systems both in new build and retrofit. This paper relates to the comparison between the two research groups about the acoustic and energy standards and low carbon measures in force in the both countries. The sound insulation requirements for residential buildings are mandatory in both Scotland and Italian building regulations. Sound insulation performance compliance is undertaken via on-site testing after completion of construction works whether new build or conversion/change of use. Importantly the specification for energy efficiency changes (and improvements) to the fabric of buildings often clash in terms of the material properties and performance functions for sound insulation. Thus, it is critically important for the specification changes in building materials for energy efficiency do not negatively impact noise and vibration sound insulation and vice versa. This can lead to non-compliance resulting in noise disturbance complaints by building occupants or loss of performance for energy efficiency. The paper characterises some of the regulatory factors, clashes in material outcomes and recommends the importance of multi-factor knowledge and understanding across building performance measures.

High Signal-to-Noise Ratio MEMS Noise Listener for Ship Noise Detection

Ship noise observation is of great significance to marine environment research and national defense security. Acoustic stealth technology makes a variety of ship noise significantly reduced, which is a new challenge for marine noise monitoring. However, there are few high spatial gain detection methods for low-noise ship monitoring. Therefore, a high Signal-to-Noise Ratio (SNR) MEMS noise listener for ship noise detection is developed in this paper. The listener achieves considerable gain by suppressing isotropic noise in the ocean. The working principle and posterior end signal processing method of the listener are introduced in detail. A gain of 10 dB over the sound pressure detector is obtained by detecting the standard sound source. In addition, the traffic vessel noise monitoring experiment verifies that the listener can detect the ship noise. The results show that the listener has a very broad application prospect in the field of low-noise ship observation.

Mechanical failure analysis of pultrusion glass fiber pipe based on acoustic emission technology

AbstractIn this study, the mechanical properties and damage modes of pultruded glass fiber/unsaturated polyester composite square pipe for automotive parts were investigated. The pipe structure, fiber mass content, dynamic mechanical analysis, tensile, and bending properties and acoustic emission detection damage mechanism of pultruded glass fiber composite pipe were studied. The structure of the cross‐section of the pultrusion pipe is like a sandwich composed of mat layers on both surfaces and a unidirectional fiber layer in middle. Based on the failure analysis of pipe by acoustic emission signal technology, it is found that the tensile damage process was considered into four stages, initial damage, mat layer fracture, intermediate damage, and fiber fracture; while the bending damage process can be divided into two stages as initial and overall damages.

Impurity-induced multi-bit acoustic topological system

Acoustic topological insulators (ATIs) are known to own topologically protected properties similar to their electronic and optical counterparts. However, for the topological insulators (TIs) with intact time-reversal symmetry (TRS), some severe defects can also induce strong backscattering. Many works try to avoid the effects of defects on topological wave transport, merely works explore the functions of the defects. Here, based on the interactions between the impurity and topological edge states, we investigate and experimentally demonstrate the capability of impurity to control and switch the valley Hall edge modes in acoustic systems. The results show the acoustic transmission spectrum is sensitive to the rotation angle of the impurity, which can be regarded as a potential platform for switchable acoustic devices or filters. Based on these discoveries, a multi-bit acoustic transmission system is designed by introducing multiple impurities into a multichannel structure, where the acoustic flows to a designated channel can be controlled by rotating impurities. Our experimental measurements match well with simulation results. The results demonstrated in this paper add a new degree of freedom in controlling ATIs and will expedite the progress of programmable acoustic information processing technology. The method of controlling topological wave transmission by impurity operations can also be applied to other systems.

Bayesian geoacoustic parameters inversion for multi-layer seabed in shallow sea using underwater acoustic field

Seabed geoacoustic parameters play an important role in underwater acoustic channel modeling. Traditional methods to determine these parameters, for example, drilling, are expensive and are being replaced by acoustic inverse technology. An inversion method based on Bayesian theory is presented to derive the structure and geoacoustic parameters of a layered seabed in a shallow sea. The seabed was considered a layered elastic medium. The objective of this research was to use the sound pressure detected by underwater acoustic sensors at different positions and to use nonlinear Bayesian inversion to estimate the geoacoustic parameters and their uncertainties in the multi-layer seabed. Specifically, the thickness, density, compression wave speed, shear wave speed, and the attenuation of these two wave speeds were determined. The maximum a posterior (MAP) model and posterior probability distribution of each parameter were estimated using the optimized simulated annealing (OSA) and Metropolis-Hastings sampling (MHS) methods. Model selection was carried out using the Bayesian information criterion (BIC) to determine the optimal model that thoroughly explained the experimental data for different parameterizations. The results showed that the OSA is much more capable of delivering high-accuracy results in multi-layer seabed models. The compression wave speed and shear wave speed were less uncertain than the other parameters, and the parameters in the upper layer had less uncertainty than those in the lower layer.

Flow current field observation with underwater moving acoustic tomography

Underwater environment observation with underwater acoustic tomography has been considerably developed in recent years. Moving sound transmission can obtain the observation of entire spatial area with sound station moving. Various internal structures, unique surface and submarine boundaries and changing environment constitutes a complex acoustic propagation channel. This paper focus on the inversion method and signal resampling for sound moving transmission. Also, the current field in three-dimensional (3D) scale is also studied. A five-station sound transmission experiment with four moored station and one moving station that conducted in range of 500m×500m at Huangcai reservoir, Changsha, China is presented. Signal resampling is performed to get correlation of received acoustic data. The vertical layer-averaged flow current results between moving station and moored station are inversed with 2D grid method. 3D flow current field result is composed by grid-averaged inversion current of vertical profile via moving station at different moment. The received results of reciprocal signal transmission between two moored stations and one moving station were used for layer-averaged current variations at vertical scale and grid-averaged current. The feasibility of the method in underwater moving acoustic tomography research is proved and its applicability is discussed. The proposed underwater acoustic tomography technology develops an innovative idea for the further development of temporal- spatial grided tomography observation.

Listening for change: quantifying the impact of ecological restoration on soundscapes in a tropical dry forest

Ecological restoration is crucial to mitigate climate change and conserve biodiversity, and accurately monitoring responses to restoration is imperative to guide current and future efforts. This study examines the impact of ecological restoration of a tropical dry forest in Central India. Here, the state forest department and a nongovernmental organization work with local communities to remove an invasive shrub, Lantana camara, in the forest, to assist natural regeneration, primarily for the purpose of improving access to forest resources for forest‐dependent people. We used acoustic technology to examine the bird community composition and the acoustic space used (ASU) across comparable restored, unrestored (with L. camara), and naturally low L. camara density (LLD) sites. We found no significant difference in the cumulative number of bird species detected between the site types (median in restored and LLD = 38, unrestored = 41). We found a significant difference in bird community composition across sites (r2 = 0.049, p ≤ 0.001). ASU differs between site types (r2 = 0.023, p ≤ 0.10), with restored sites positively associated with ASU compared to unrestored and LLD sites, which could represent a temporary increase in ASU as animal communities are reorganized after the complete removal of L. camara. Our results suggest that small‐scale restoration efforts that aim to help meet livelihood needs have the potential to contribute to ecological goals in this landscape. However, it is necessary to continue to monitor the regeneration trajectory in restored sites and the possible changes in the ASU.

Inversion of shallow seabed structure and geoacoustic parameters with waveguide characteristic impedance based on Bayesian approach

Underwater acoustic technology is essential for ocean observation, exploration and exploitation, and its development is based on an accurate predication of underwater acoustic wave propagation. In shallow sea environments, the geoacoustic parameters, such as the seabed structure, the sound speeds, the densities, and the sound speed attenuations in seabed layers, would significantly affect the acoustic wave propagation characteristics. To obtain more accurate inversion results for these parameters, this study presents an inversion method using the waveguide characteristic impedance based on the Bayesian approach. In the inversion, the vertical waveguide characteristic impedance, which is the ratio of the pressure over the vertical particle velocity, is set as the matching object. The nonlinear Bayesian theory is used to invert the above geoacoustic parameters and analysis the uncertainty of the inversion results. The numerical studies and the sea experiment processing haven shown the validity of this inversion method. The numerical studies also proved that the vertical waveguide characteristic impedance is more sensitive to the geoacoustic parameters than that of single acoustic pressure or single vertical particle velocity, and the error of simulation inversion is within 3%. The sea experiment processing showed that the seabed layered structure and geoacoustic parameters can be accurately determined by this method. The root mean square between the vertical waveguide characteristic impedance and the measured impedance is 0.38dB, and the inversion results accurately represent the seabed characteristics in the experimental sea area.