Acoustic Technology Research Articles

An auditory virtual reality of meeting room acoustics using wave-based acoustic simulations: A content for intuitive understanding of room-acoustics control effect by sound absorbers

Recently, wave-based room acoustic simulation technologies are becoming a realistic option as a small-room acoustics design tool and a virtual indoor sound environment creation tool for research and education. The present paper shows an auditory VR meeting room content, which makes us easily understand how sound absorbers play an essential role in creating a better acoustic environment. Unity creates the 3D virtual reality model, and a binaural room-acoustic auralization is realized by a hybrid technique combined with Ambisonics and the head-related transfer function using RIRs computed by a high-speed parallel wave-based room acoustics solver. The VR meeting room is constructed under various acoustic treatments with sound absorber modeling by wave-based material models.

Acoustic emission characteristics of stainless steel reinforced geopolymer coral concrete beams under four-point bending

The fabrication of geopolymer coral aggregate concrete beams (GCACB) can effectively address the challenges associated with constrained concrete raw materials and structural erosion in island construction. Acoustic emission technology (AE) presents an appealing solution for non-destructive evaluation and structural health monitoring. In this study, 6 specimens were conducted to examine the flexural behavior of GCACB accounting for variation in the reinforcement ratios under the four-point bending test, simultaneously recording the corresponding AE data. Then, the effect of the AE parameters on crack development was analyzed. By utilizing the GMM algorithm, the crack pattern classification was investigated. Finally, the GCACB damage was evaluated based on two different AE b-value analysis methods. The findings indicate that the cracks within GCACB predominantly occur along the coral coarse aggregate with low strength and high brittleness. The presence of reinforcement ratio has an enhancement on both the flexural capacity and deformation capacity of GCACB while impeding the crack width. It seems that a positive correlation between increasing crack damage and cumulative hits and AE energy occurs. Based on the enhanced GMM model, the cracks are categorized into tensile crack, shear crack, and mixed crack, with tensile crack predominating. A probabilistic division line is established for the RA-AF relationship that progressively leans towards the AF axis as the reinforcement ratio increases. In contrast to the b-value obtained from the GBR method, the Aki method demonstrates enhanced predictive capability for GCACB damage.

A framework to simulate and to auralize the sound emitted by aircraft engines

In civil aviation, the well-established Effective Perceived Noise Level (EPNL) has remained, so far, a simple but reliable psycho-acoustic metric, representing the backbone of noise regulation politics and leading to quieter aircraft turbofan engines. However, the recent changes induced by further acoustic optimization of engines, or the introduction of innovative designs, suggest that a more refined assessment than the sole EPNL metric is needed, which is based on sound auralization. The paper presents a framework of simulation tools that are currently being developed at the DLR Engine Acoustics Department with the goal of assessing novel designs at a very early development stage. This framework allows to simulate acoustically an engine flyover and to produce audible signals as perceived by a virtual observer standing on the ground. The source calculation is performed by the tool PropNoise and relies on analytical physics-based models for the fan noise sources, and Stone's semi-empirical jet noise model. The subsequent tool VIOLIN simulates the propagation of sound through the atmosphere and the ground reflection effects. Finally, the spectrograms of the broadband and tonal noise components are converted to audible sound by the auralization tool CORAL. The procedure is applied to a realistic engine test case and compared with experimentally recorded sound.

Ecology Health Evaluation System Based on Fish Movement Behavior Response

Using fish as indicator organisms to monitor water quality can accurately reflect the pollution status of aquatic environments in real time. Currently, there are limited quantitative and empirical studies on fish movement behavior. An experimental study on the fish movement behavior response during water quality change was conducted using an aquatic environment model. Advanced acoustic tag monitoring technology was used to qualitatively and quantitatively assess fish movement. Using the temporal and spatial distributions of fish motion behavioral trajectories during water quality change, the fish behavior response indicators were the distance between the fish and the source of pollution, the distance between the fish and the water surface, and fish swimming speed. The fish were sensitive to water quality factors, including dissolved oxygen (DO) content, microcystin aeruginosa toxin (MC-LR), and non-ionic ammonia (NH3). The correlations between indicator pairs were analyzed. A new water ecological health evaluation system based on these indicators was constructed, and aquatic ecological health in the field was evaluated using the new system. The evaluation showed a sub-healthy state in spring and a slightly morbid to morbid state in summer, which was consistent with the results based on water quality indices. The accuracy of the proposed assessment system was verified. This showed that the assessment method and grade division of the assessment system were reasonable and feasible and could reflect the health status of the aquatic ecological environment in real time. This study provides a basis for the assessment of the health and restoration effects of the aquatic ecological environment.

Three-point bending damage detection of GFRP composites doped with graphene oxide by acoustic emission technology

The incorporation of graphene oxide (GO) into composite materials can modulate their overall performance. To enhance the performance of acoustic emission (AE) signals, 3% GO was incorporated into glass fiber-reinforced polymer (GFRP) composites, resulting in the creation of GO-GFRP composite materials. The sentry function was first used to investigate the damage evolution of the material. Then, the AE signals were analyzed using multivariate mode decomposition (MVMD) and the generalized S transform to identify the damage mechanisms. Finally, scanning electron microscopy (SEM) was used to observe the fracture surfaces of the samples to confirm the material failure. The experiments identified four damage mechanisms: matrix cracking, fiber debonding, delamination failure, and fiber breakage. It was also found that GO-GFRP composites are more prone to fiber debonding compared to GFRP composites without added GO.

Directional and lattice engineering growth of sapphire fibers for ultrasonic ultra-high-temperature sensors

High-temperature sensors for extreme environments are in urgent demand with the rapid development of aerospace, nuclear energy, and advanced manufacturing. Ultrasonic temperature sensors (UTS) are widely used in high-temperature sensing due to their high working temperature that approaches the melting point of the acoustic waveguide. Al2O3 single-crystal fiber (SCF), also called sapphire fiber, is a promising candidate for ultrasonic thermometry due to its ultra-high melting point (∼2050 °C), high strength and oxidation resistance. Here, we report for the first time, to the best of our knowledge, large length-diameter ratio sapphire fibers with specific orientations (a-axis, m-axis, and c-axis) have been grown by laser-heated pedestal growth method and applied for ultrasonic temperature sensing. Sapphire fibers exhibit significant acoustic anisotropy, and a-oriented sapphire fiber has a lower acoustic velocity and a greater velocity-temperature variation, leading to higher sensitivity. Moreover, the acoustic velocity of sapphire fiber could be further decreased by doping with Cr ions owing to the enhanced lattice disorder and crystal density. As a result, an improved unit sensitivity of 28.98–52.88 ns°C−1m−1 and a superior resolution of 1.73–0.95 °C have been achieved in the range of 20–1200 °C via a-oriented Cr:Al2O3 SCF-UTS. More importantly, the sensor performance is positively correlated with ambient temperature, accompanied with the high working temperature (∼1800 °C) and excellent stability (∼20 h), demonstrating promising prospects for applications in high-temperature thermometry. This work provides a feasible approach for designing a high-performance UTS based on acoustic anisotropy and lattice engineering.

Bayesian acoustic emission time-difference method for locating the collision point of sweeping robot shell

The existing source localization based on acoustic emission technology often depends on the assumption of constant wave velocity inside the material. However, this assumption is hardly satisfied in actual engineering. The uncertainty of wave velocity can easily lead to low localization accuracy of sweeping robots. To overcome these deficiencies, a complete probability multi-directional measurement method based on the Bayesian inference mechanism is proposed. In the proposed method, based on the Bayesian probabilistic model, the extracted sensor time difference is subjected to probabilistic inference using the coordinate input model to determine the posterior distribution of the source’s position and wave velocity of the given arrival time. Compared with the traditional time-difference method, the proposed method achieves excellent results and outperforms the standard time-difference method in localization accuracy and anti-interference. In addition, the proposed method can conveniently, quickly, and effectively determine the location of the colliding point without considering the source emission time and wave velocity. The research in this paper provides an effective method for solving the collision localization problem of the sweeping robot shell under the acoustic emission time and wave velocity are unknown.

Fourier transformation for acoustic: Principle & applications

A The Fourier transform has a wide range of applications in daily life, including physics, signal processing, acoustics etc. The topic of this article is to demonstrate the principle and applications of the Fourier transform in acoustics through theoretical derivation. The paper first derived the basic formula of the Fourier Transform and the related seven theorems. Then the paper detailed the research of Fourier Transform in underwater acoustic pulse signal detection technology. Finally, the application of Fourier Transform in the defect detection algorithm of MEMS acoustic films was detailed. According to the analysis, the paper demonstrated the primary application of Fourier Transform in underwater acoustic pulse signal detection and defect detection algorithm of MEMS acoustic film. Based on the evaluations, this study demonstrated the general application scenario of Fourier Transform and offered theoretical basis of its application in acoustic field, which promotes its developmental potential in the acoustic field. Overall, these results shed light on guiding further exploration of acoustic research.

VGGish-based detection of biological sound components and their spatio-temporal variations in a subtropical forest in eastern China.

Passive acoustic monitoring technology is widely used to monitor the diversity of vocal animals, but the question of how to quickly extract effective sound patterns remains a challenge due to the difficulty of distinguishing biological sounds within multiple sound sources in a soundscape. In this study, we address the potential application of the VGGish model, pre-trained on Google's AudioSet dataset, for the extraction of acoustic features, together with an unsupervised clustering method based on the Gaussian mixture model, to identify various sound sources from a soundscape of a subtropical forest in China. The results show that different biotic and abiotic components can be distinguished from various confounding sound sources. Birds and insects were the two primary biophony sound sources, and their sounds displayed distinct temporal patterns across both diurnal and monthly time frames and distinct spatial patterns in the landscape. Using the clustering and modeling method of the general sound feature set, we quickly depicted the soundscape in a subtropical forest ecosystem, which could be used to track dynamic changes in the acoustic environment and provide help for biodiversity and ecological environment monitoring.

A challenge to the evidence behind noise guidelines for UK hospitals.

Teams assessing hospital noise against international guidelines regularly find that noise exceeds perceived safe levels in clinical settings. The care of sick people may be inherently noisy but recent efforts to tackle the problem propose a wider scope to identify sources and qualities of noise as well as more precision with noise recording. We sought to challenge the scientific evidence cited in the four major documents pertaining to hospital noise in the UK to clarify if evidence of harm from noise included in guidelines is available, contemporary and of high quality. Our team of hearing-health clinicians, acoustic scientists and acoustic engineers have conducted a narrative scoping review focused on critically appraising four of the most cited guidelines against which noise is measured in healthcare settings in the UK. There is a lack of high-quality evidence for commonly accepted consequences of noise cited in current guidelines. The current evidence base for noise guidelines in a healthcare setting is largely based on subjective heterogeneous and inconclusive research. Whilst reduced noise is not disputed as potentially beneficial for patient care, further hypothesis-driven research and interventions assessing the benefits or outcomes of any such intervention should be sought to produce high-quality evidence of relevance on the clinical coalface.

Study on Low-Temperature Performance Decay of Composite-Modified Porous Asphalt Mixture under Medium- and High-Temperature Water Erosion.

This paper studies the decay law of low-temperature crack resistance performance of rubber powder basalt fiber composite-modified porous asphalt concrete (CM-PAC) under medium- and high-temperature water erosion. Firstly, the prepared Marshall specimens were subjected to water erosion treatment at different temperatures of 20 °C, 40 °C, and 60 °C for 0-15 days. Then, the processed specimens were subjected to low-temperature splitting tests, and acoustic emission data during the splitting test process were collected using an acoustic emission device. It can be seen that the low-temperature splitting strength and low-temperature splitting stiffness modulus of CM-PAC gradually decrease with the increase in water erosion time. The maximum reduction rates of the two compared to the control group reached 72.63% and 91.60%, respectively. The low-temperature splitting failure strain gradually increases. Under the same erosion time, the higher the temperature of water, the more significant the amplitude of changes in the above parameters. In addition, it is shown that as the water erosion time increases, the first stage of loading on the specimen gradually shortens, and the second and third stages gradually advance. As the water temperature increases and the water erosion time prolongs, the acoustic emission energy released by the CM-PAC specimen during the splitting process slightly decreases. The application of acoustic emission technology in the splitting process can clarify the changes in the failure pattern of CM-PAC specimens during the entire loading stage, which can better reveal the impact of medium- to high-temperature water on the performance degradation of CM-PAC.

Preparation of NCh-B and NCh-B-Ti nanocomposites and their ignition and combustion performances

To overcome the agglomeration and insufficient combustion of nano-boron (n-B) powders, this study successfully prepared two novel types of boron-based nanocomposites using the acoustic resonance technology, namely high-substitute nitrochitosan/nano-boron (NCh-B) with ratios of 1:3, 1:5, 1:7 and 1:9, and nitrochitosan/nano-boron powder/nano-titanium (NCh-B-Ti) with Ti contents of 5 wt%, 10 wt%, 15 wt% and 20 wt%. The structural morphologies, laser ignition and combustion properties of the composites were systematically investigated. The results suggest that the addition of NCh can significantly improve the dispersion of n-B. NCh-B exhibited a higher combustion performance than n-B, as evidenced by their ignition delay and flame areas. When the laser power density was 81 W, NCh-B5-Ti15% exhibited a combustion time and an ignition delay of 240 ms and 5.5 ms respectively, which were higher and lower than those of NCh-B5 (199 ms and 17 ms, respectively). Furthermore, NCh-B5-Ti15% displayed a lower ignition delay than both n-B powders (12 ms) and NCh-B (11 ms), as well as brighter flames and a larger combustion area. Therefore, the addition of n-Ti can promote the combustion of n-B powders, with the combustion products of NCh-B-Ti including H3BO3, B2O3, TiB2, and TiO. This study provides a new method for improving the ignition performance and combustion efficiency of n-B powders.

Analysis of High-Frequency Communication Channel Characteristics in a Typical Deep-Sea Incomplete Sound Channel

Deep-sea acoustic communication has attracted widespread attention in recent years. Research on deep-sea acoustic communication channel characteristics is essential for the development and system design of deep-sea acoustic communication technologies. However, the structural and spatiotemporal characteristics of deep-sea high-frequency acoustic communication channels (unlike those of shallow-water acoustic communication channels) are poorly understood. Based on a channel measurement experiment in a typical deep-sea incomplete sound channel environment in the South China Sea, this paper analyzes the structural and spatiotemporal characteristics of high-frequency underwater acoustic channels in the direct-arrival and shadow zones. The channel multipath vertical structure, amplitudes of different path clusters, root mean square (RMS) delay spread, and channel temporal coherence are investigated at different depths. The randomness of different path clusters is quantified as the coefficient of variation. The channels in the shadow zone are characterized by a complex multi-path structure, high RMS delay spread, and low temporal coherence. On the contrary, the channels of the direct-arrival zone show multi-path convergence, low RMS delay spread, and high temporal coherence. Understanding the dynamic changes in these parameters can guide the statistical modeling of channels and the design of communication algorithms in different zones in deep-sea high-frequency acoustic communication scenarios.

Use of Resonant Acoustic Mixing Technology for Ultra-Low-Dose Blending in a Single-Step Mixing Process.

To evaluate the use of resonant acoustic mixing (RAM) technology for homogenous blending of a morphologically challenging model API in low-dose concentrations (<0.1% w/w), and assess the potential for blend uniformity (BU) optimization. Caffeine (CAF) mixing was carried out using a LabRAM I benchtop mixer. Uniformity was assessed under a range of mixing conditions and sample preparation procedures in order to optimize system performance. The capacity for microscale mixing was evaluated from final parameters for 0.05% and 0.0125% CAF blends. Upon optimization, RAM was able to accurately prepare homogeneous mixtures of <0.1% CAF in dilutions of up to 1 part per 8,000. Results from a 0.05% blend targeting 125 μg CAF dosage amounts revealed an AV score of 8.8 while a 0.0125% w/w blend accurately prepared 25 μg of CAF with 99.3% accuracy (98.7% label claim) and AV of 10.1. Microscale mixing in the 0.05% w/w blend was confirmed from plots of BU data against sample size demonstrating a slope of 0.05 within the range of 250-10 mg sample (125-5 μg CAF). L1 BU criteria only failed at the level of 2 μg CAF, despite target precision to 26 nanograms (98.7% label claim). This study presents the first instance of a homogenously mixed <0.1% (w/w) blend using RAM technology and demonstrate the suitability for reproducible dosing of single-digit microgram drug amounts. Uniformity is documented for API amounts 60x smaller than a recent report has shown and 10,000x smaller than achieved previously with CAF.

Multiple broadband gaps and vibration suppression mechanisms for innovative star shaped metamaterial structures with triangular characteristics

Metamaterials have received extensive attention due to their special properties in the fields of wave attenuation and acoustic engineering. Many researchers have designed metamaterials with different band gap frequency ranges. In this paper, a star shaped metamaterial structure with triangular characteristics is proposed to attenuate mid and low frequency elastic waves in practical applications. The band gap and dispersion characteristics of the structure are numerically studied. The results show that the structure generates ultra-wide band gaps in the frequency range of 6000 Hz, accounting for up to 69.14%. Interestingly, by adding a support structure to the original structural unit, the bandwidth of the improved structure reached 73.89%, and multiple band gaps were opened within 2000 Hz. Finally, the vibration transmission loss of the structure is analyzed by finite element method, and the control performance of vibration transmission in periodic structures is simulated, demonstrating its potential in practical applications.

Whole-lake acoustic telemetry to evaluate survival of stocked juvenile fish

Estimates of juvenile survival are critical for informing population dynamics and the ecology of fish, yet these demographic parameters are difficult to measure. Here, we demonstrate that advances in animal tracking technology provide opportunities to evaluate survival of juvenile tagged fish. We implemented a whole-lake telemetry array in conjunction with small acoustic tags (including tags < 1.0 g) to track the fate of stocked juvenile cisco (Coregonus artedi) as part of a native species restoration effort in the Finger Lakes region of New York, USA. We used time-to-event modeling to characterize the survival function of stocked fish, where we infer mortality as the cessation of tag detections. Survival estimates revealed distinct stages of juvenile cisco mortality including high immediate post-release mortality, followed by a period of elevated mortality during an acclimation period. By characterizing mortality over time, the whole-lake biotelemetry effort provided information useful for adapting stocking practices that may improve survival of stocked fish, and ultimately the success of the species reintroduction effort. The combination of acoustic technology and time-to-event modeling to inform fish survival may have wide applicability across waterbodies where receiver arrays can be deployed at scale and where basic assumptions about population closure can be satisfied.

Opportunistic Hybrid Routing Protocol for Acoustic-Radio Cooperative Networks

The ocean contains abundant resources and has high scientific and economic values. Increasing underwater communication scenarios stimulates many research efforts on underwater wireless ad-hoc networks. Underwater acoustic communication technology supports medium to long-range wireless communication. However, it suffers from low transmission data rates and long link delays. This paper introduces an Acoustic-Radio Cooperation Network (ARCNet) model for more efficient maritime information transmission. Under this ARCNet, we propose a new Radio-Acoustic Opportunistic Hybrid (RAOH) routing protocol composed of a neighbor discovery mechanism and a hybrid routing strategy. In the neighbor discovery stage, we explore the surface radio links to aid in selecting the shortest delay path between an underwater node and the surface nodes. In the route establishment stage, we combine the advantages of opportunistic routing and on-demand routing and design an opportunistic hybrid routing strategy, which improves the success rate of data forwarding and reduces the time spent on route establishment. Simulation results show that the proposed RAOH protocol outperforms traditional terrestrial and underwater routing strategies in routing response speed, packer delivery rate, throughput, end-to-end delay, and energy efficiency.

Fracture behaviour characterisation of FRP-reinforced concrete based on digital image correlation and acoustic emission technology

In order to identify the dynamic fracture characteristics of fibre-reinforced polymer (FRP)-reinforced concrete, three-point bending fracture tests of FRP-reinforced concrete with five different strain loading rates (10−1/s, 10−2/s, 10−3/s, 10−4/s and 10−5/s) are carried out. The fracture behaviour of FRP-reinforced concrete is analysed using digital image correlation (DIC) and acoustic emission (AE) techniques. Crack propagation in FRP-reinforced concrete beams during the fracture process is observed and a quantitative relationship is established between the AE parameters and the load level before the ultimate load is reached. Test results on the variation of the AE parameters can characterise the internal damage behaviour of the FRP-reinforced concrete beams and monitor the distribution characteristics of any cracks. The crack propagation trajectory of the FRP-reinforced concrete beams can be observed using the DIC technique and quantitative analysis of the crack opening displacement (COD) can be achieved.

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Simulation and discussion of typical radio frequency filters

The demand for filters is increasing as the frequency bands for 5G expand. RF filters become the segment with the largest market share of RF front-end chips. More crowded frequency bands, as well as thinner and lighter communication equipment, necessitate higher filter performance. In this paper, several technologies for the implementation of Radio Frequency filter are presented. Essentially three types are considered: (i) Lumped Element (LC) Filter and Integrated Passive Devices (IPD) technology; (ii) Acoustic Wave Filter; and (iii) a composite filter design that combines acoustic and IPD technologies. Benefits and drawbacks of these diverse configurations in terms of their technical performance and current applications are examined, and several models are presented and simulated using ADS software.