Acoustic Control Research Articles

Wind power prediction through acoustic data-driven online modeling and active wake control

Accurate online prediction of wind power is essential for the reliable operation of power systems. However, the precision of wind turbine power forecasts is often hindered by wake effects and inadequate online modeling capabilities. To tackle this issue, this paper proposes a data-driven online prediction method for wind turbine power, leveraging acoustic data for training. The approach involves a neural network that learns acoustic feature changes related to wind output power, by enhancing the kernel extreme learning machine (KELM) technique and applying data augmentation. Additionally, to address the wake effects in real wind fields, active wake control is integrated, considering that most wind turbines operate in the wake of upstream turbines. Experiments using actual wind tunnel measurement data were conducted to assess the performance of the proposed method. The findings demonstrate that this method surpasses other techniques without increasing computational costs. The mean absolute error (MAE) of the proposed method was only 0.4111 and 0.4302, and the root mean square error (RMSE) was just 0.4868 and 0.5195, respectively, in both experiments. Moreover, the proposed acoustic data-driven online power prediction method proves stable in high background noise environments and achieves accurate wind power prediction with just a 10% data sample following the implementation of the active wake control strategy. This work significantly contributes to the efficient utilization of wind energy resources.

Coupled topological edge and corner states in two-dimensional phononic heterostructures with nonsymmorphic symmetries

The exciting discovery of topological phononic states has aroused great interest in the field of acoustic wave control. However, conventional topological edge states and corner states localized at the interface and corner of the two-phase domain wall structures are limited by single channel transmission characteristics, which decreases the flexibility of designing multi-channel acoustic wave devices. Here, we propose a two-dimensional (2D) topological phononic heterostructure with nonsymmorphic symmetries to realize the multiple interface topological multimode interference effect based on the coupling of topological edge and corner states. Topological phase transitions are achieved by altering the rotation angle of the split-ring scatterers in a square lattice. The coupled edge states are generated by the coupling between the edge states of ordinary-topological-ordinary (OTO) interfaces. Moreover, the higher-order topology of the square phononic crystals (PCs) is characterized by nontrivial bulk polarization, the topological and coupled corner states splitting into two pairs appear in the square OTO bend structure owing to the nonsymmorphic PC lack of mirror symmetries. Finally, the topological robustness of the multimode interference effect of coupled edge and corner states against defects is demonstrated. Our results pave the way for guiding and trapping acoustic waves in topological nonsymmorphic heterostructures, whose multi-channel transmission capability can be employed for designing topological phononic filters, couplers and multiplexers.

Sound transmission loss and bending properties of sandwich structures based on triply periodic minimal surfaces

Four types of triply periodic minimal surfaces sandwich structures (TPMS-SS), namely, G-SS, D-SS, D1-SS, and IWP-SS, have been proposed. The bending properties were evaluated by experiments and numerical simulations, and their sound insulation performance was investigated using theoretical, numerical and experimental methods. Firstly, the bending performance of four TPMS-SS was compared. Then, the acoustic vibration control equation of TPMS-SS was established and the theoretical solution for the sound transmission loss (STL) was derived based on Reissner's theory combined with the fluid-solid coupling condition. Next, experimental study was conducted on the STL performance of TPMS-SS using the impedance tube method, and the numerical model was verified using theoretical and experimental results. Finally, parametric studies were carried out to investigate the effects of parameters such as relative density (RD), panel thickness (hf), and sound incidence elevation angle (φ), as well as the type of structure, on the STL performance. The results show that TPMS-SSs can achieve >30 dB of STL in the frequency range of 1 Hz to 10 kHz. The STL value increases with relative density (RD), panel thickness (hf), and sound incident elevation angle (φ), while the location of the dips in the STL curves is affected by relative density and panel thickness. G-SS has the best bending performance, while D1-SS has the best acoustic performance. The results could be used for the optimization design of lightweight sandwich structures.

Optimized PI-PDF active structural acoustic control of smart FG GPL-reinforced closed-cell metallic foam sandwich plate

This study investigates Active Structural Acoustic Control (ASAC) applied to sandwich plates featuring Functionally Grade (FG) porous Graphene-Platelet-Reinforced Piezoelectric (GPLRP) materials. These plates incorporate a core layer with internal pores and GPLs dispersed in a metal matrix, along with piezoelectric sensors and actuators. Using a spatial state-space formulation based on linear 3D piezoelasticity theory, a semi-analytical solution is derived for the vibroacoustic response of these sandwich plates. The mechanical properties of the porous core are modeled using a closed-cell metal foam. The effects of various parameters, including porosity distributions, porosity coefficient, weight fractions of nanofiller, and geometric parameters on the radiation efficiency and radiated sound power have been investigated. Then, the validation of the proposed model is examined by comparing the natural frequencies calculated in the present study to those from the literature. This comparison allows us to assess the accuracy and reliability of our model against established findings. Radiated sound power reduction from mechanically excited structures is achieved by employing a dual-stage Proportional Integral–Proportional Derivative with Filter (PI-PDF) controller, optimized using Grey Wolf Optimization (GWO). Finally, several numerical simulations are conducted to validate the effectiveness and accuracy of the proposed active control strategy.

Preface

12th International Scientific Conference of The Military Technical College 21-23 May, 2024 Conference Program of The 21St International Conference on Applied Mechanics and Mechanical Engineering, (AMME-21) Cairo 2024 The military Technical College has the pleasure to organize the 21St International Conference on Applied Mechanics and Mechanical Engineering, (AMME-21) which is sponsored by the Ministry of Defense in the period 21-23 May, 2024. The main objective of this conference is to bring together scientific researchers and engineers of Egyptian armed forces and their colleages in the international academic and industrial institutions. This occasion provides a chance to exchange information in the following designated fields of interest 1- Mechanical Power Engineering MP 2- Robotic, Automation and Control RC 3- Dynamics and Vibration DV 4- Material Science and Processing MS 5- Production Technology PT 6- Solid Mechanics SM 7- Mechanical Design MD 8- Automotive Engineering AE 9- Mechatronics MC 10- Ballistics BL 11- Acoustics and Noise Control AN From the manuscripts submitted to the conference secretary, 41 papers have been accepted. These selected papers will be presented during the conference interval 21-23 May 2024 in 10 sessions. Finally, the conference committee hopes that the conference will achieve its planed mission and would like to acknowledge all contributors, membes of scientific committees, chairman and board members of the conference sessions. Note: Please remember that you have only 15-h20 min. to present your paper and 5 min. for discussion Prof. Dr. Shawky A. Hegazy AMME-21 Conference Rapporteur List of Conference Committee, Contributors, Conference Program, Location of Conference Halls, Part I: Scientific Sessions, Part II: Seminars / Invited talk and Part III: Authors Index are available in this Pdf.

Focused ultrasound enables selective actuation and Newton-level force output of untethered soft robots

Untethered miniature soft robots have significant application potentials in biomedical and industrial fields due to their space accessibility and safe human interaction. However, the lack of selective and forceful actuation is still challenging in revolutionizing and unleashing their versatility. Here, we propose a focused ultrasound-controlled phase transition strategy for achieving millimeter-level spatially selective actuation and Newton-level force of soft robots, which harnesses ultrasound-induced heating to trigger the phase transition inside the robot, enabling powerful actuation through inflation. The millimeter-level spatial resolution empowers single robot to perform multiple tasks according to specific requirements. As a concept-of-demonstration, we designed soft robot for liquid cargo delivery and biopsy robot for tissue acquisition and patching. Additionally, an autonomous control system is integrated with ultrasound imaging to enable automatic acoustic field alignment and control. The proposed method advances the spatiotemporal response capability of untethered miniature soft robots, holding promise for broadening their versatility and adaptability.

Pars Opercularis Underlies Efferent Predictions and Successful Auditory Feedback Processing in Speech: Evidence From Left-Hemisphere Stroke.

Hearing one's own speech allows for acoustic self-monitoring in real time. Left-hemisphere motor planning regions are thought to give rise to efferent predictions that can be compared to true feedback in sensory cortices, resulting in neural suppression commensurate with the degree of overlap between predicted and actual sensations. Sensory prediction errors thus serve as a possible mechanism of detection of deviant speech sounds, which can then feed back into corrective action, allowing for online control of speech acoustics. The goal of this study was to assess the integrity of this detection-correction circuit in persons with aphasia (PWA) whose left-hemisphere lesions may limit their ability to control variability in speech output. We recorded magnetoencephalography (MEG) while 15 PWA and age-matched controls spoke monosyllabic words and listened to playback of their utterances. From this, we measured speaking-induced suppression of the M100 neural response and related it to lesion profiles and speech behavior. Both speaking-induced suppression and cortical sensitivity to deviance were preserved at the group level in PWA. PWA with more spared tissue in pars opercularis had greater left-hemisphere neural suppression and greater behavioral correction of acoustically deviant pronunciations, whereas sparing of superior temporal gyrus was not related to neural suppression or acoustic behavior. In turn, PWA who made greater corrections had fewer overt speech errors in the MEG task. Thus, the motor planning regions that generate the efferent prediction are integral to performing corrections when that prediction is violated.

Acoustic analysis and control measures for noise in university: a case study of Adrar University, Algeria

The purpose of this research is to investigate the complex dynamics of noise pollution at the University of Adrar-Algeria, with a particular emphasis on the impact that the dry desert climate has on the acoustic environment of the campus. With the goal of cultivating an environment that is characterised by tranquilly, comfort, and optimal conditions for attention, learning, and practical engagement, the research attempts to achieve the goal of enhancing the existing discourse on noise management inside academic institutions. The inquiry makes use of a methodical approach in order to investigate the many climatological characteristics that are unique to the desert climate and that lead to increased noise levels within the university grounds. In addition, the research investigates the ways in which noise emissions from various sources alter inside the confines of Adrar University, taking into account the ways in which the harsh desert climate influences the parameters that control these emissions. The investigation of human behaviour patterns is relevant to this investigation. In particular, the investigation will focus on instances of protracted assemblage in air-conditioned places, which correlates with increased noise levels. In light of the fact that noise control is an essential component of the academic environment, the research being conducted at the University of Adrar includes the collection of questionnaires, the administration of on-site sound measurements, and the creation of an all-encompassing noise map. The findings shed light on the climatic factors that are primarily responsible for the excessive amount of noise that exceeds the standards that are suggested by the World Health Organisation (WHO).

Acoustic Pressure Amplification through In-Duct Sonic Black Holes

Acoustic detection of machinery defaults from in-duct measurements is of practical importance in many areas, such as the health assessment of turbines in ventilation systems or engine testing in the surface and air transport sectors. This approach is, however, impeded by the low signal-to-noise ratio (SNR) observed in such environments. In this study, it is proposed to exploit the slow sound effect of Sonic Black Hole (SBH) ducted silencers to enhance the sensing of incident pulse acoustic signals with low SNR. It is found from transfer matrix and finite element modelling that fully opened SBH silencers with perforated skin interfaces are able to substantially enhance an incident pulse amplitude while channeling an air flow. We demonstrate that the graded depths of the SBH cavities provide rainbow spectral decomposition and amplification of the incident pulse frequency components, provided that impedance matching, slow sound, and critically coupled conditions are met. In-duct experiments showed the ability of a 3D printed SBH silencer to simultaneously enhance acoustic sensing and fully trap the pulse spectral components in the SBH cavities in the presence of a low-speed flow. This study opens up new avenues for the development of dual-purpose silencers designed for acoustic monitoring and noise control in duct systems without obstructing the air flow.

Numerical investigation of acoustic streaming vortices in cylindrical tube arrays

Abstract Acoustic streaming has a significant effect on accelerating material mixing and flow field disturbance. To explore the characteristics of acoustic streaming in the cylindrical tube array field under the action of an acoustic wave, we derive the dimensionless acoustic streaming control equation and establish a numerical calculation model of acoustic streaming. The effects of acoustic incidence angle, acoustic Reynolds number, and Strouhal number on the acoustic streaming vortex flow field in the tube array were investigated. The numerical results show that with the change in acoustic parameters, the acoustic streaming in the tube array presents rich changes in the vortex flow field, and there are flow field phenomena such as shrinking, merging, tearing, and splitting of the vortex structure. Toward the walls of each tube, there is a strong acoustic streaming flow velocity. Besides, there is also a large streaming velocity on the interface of the adjacent acoustic streaming vortices. The inner streaming vortex structure in the acoustic boundary layer decreases with the increase in the acoustic Reynolds number, but the intensity of the inner streaming vortex and outer streaming vortex increases rapidly, and the disturbance effect of the flow field is enhanced. With the increase in the dimensionless acoustic frequency (or Strouhal number), although the structure and intensity of the inner streaming vortex decrease, the velocity gradient on the wall of the cylindrical tube increases, which is beneficial to destroy the flow boundary layer of the cylindrical tube wall and accelerate the instability of the wall flow field.

Acoustic Signal-Based Robotic Cutting Depth Control Under Uncertain Bone Layer Distribution

Acoustic Signal-Based Robotic Cutting Depth Control Under Uncertain Bone Layer Distribution

The architecture design checklist of classrooms for children with cochlear implant in rehabilitation centers

Children with cochlear implants (CI) have unique physical, psychological, and behavioral needs compared to typically developing children, thus they go through a rehabilitation process for education and activity purposes in a rehabilitation center (RC). The provision of specialized support for children with CI reflects a nation's commitment to inclusivity and care for all segments of society. This study investigates the research gab of the needs of children with CI (aged 1–6) to identify the fundamental design requirements in order to develop an architectural design checklist for their classrooms. Through literature review and comparisons with standard preschool designs for typically developed children, the research identifies key design elements affecting these children's learning and integration. This study establishes a framework for optimizing RC's classroom design for children with CI. Following a methodological discussion addressing pertinent research considerations, a comprehensive user experience questionnaire was conducted. The questionnaire included participants from various stakeholder groups: parents, educators, medical professionals (psychiatrists and doctors), and design experts (architectural and acoustic engineers). The findings inform the identification of essential design elements encompassing layout, materials selection, ventilation strategies, lighting systems, acoustic control measures, and color palettes. Following analysis, the research concludes with a design checklist outlining optimal ranges (100 % = sub-optimum, 50 % = optimum, 0 % = over design) for each element, including furniture layout, color schemes, materials, classroom shape, lighting, and ventilation. This checklist ensures RC classrooms effectively cater to the specific needs of children with CI.

Tunable acoustic transmission control and dual-mode ventilated sound insulation by a coupled acoustic metasurface

Tunable acoustic transmission control and dual-mode ventilated sound insulation by a coupled acoustic metasurface

Analyzing the impact of flexible shells and sound absorbent lining on acoustic wave behavior in ducts

This study focuses on investigating the propagation of acoustic waves in a cylindrical waveguide with higher‐order derivative‐based boundary conditions and a sound absorbent lining. The mode‐matching method is employed to solve the governing boundary value problem, utilizing continuity conditions for pressure and velocity at waveguide interfaces. The objective is to establish a theoretical framework for analyzing and optimizing the acoustic performance of the waveguide, considering the influence of crucial parameters. The study's findings hold significant practical implications in acoustic engineering and noise control, enabling accurate prediction of acoustic wave behavior and facilitating the design of effective noise reduction measures and optimized sound‐absorbing materials in various applications. Additionally, the numerical techniques developed here can be extended to address more complex waveguide geometries and boundary conditions.

Toward Fatigue-Tolerant Design of Additively Manufactured Strut-Based Lattice Metamaterials

Abstract The advent of additive manufacturing (AM) has enabled the prototyping of periodic and non-periodic metamaterials (a.k.a. lattice or cellular structures) that could be deployed in a variety of engineering applications where certain combinations of performance features are desirable. For example, these structures could be used in a variety of naval engineering applications where lightweight, large surface area, energy absorption, heat dissipation, and acoustic bandgap control are desirable. Furthermore, combining the multifunctional design optimization of these structures with progressive degradation due to cyclic loading could lead to fatigue-activated attritable systems with potentially tailorable performances not yet in reach by current conventional systems. Nevertheless, in order to deploy these complex geometry structures their multiphysics response has to be well understood and characterized. The objective of the current effort is to describe an initial approach for designing a uniaxial metamaterial specimen for fatigue testing as the first step toward the design of multi-axial fatigue test coupons. In order to compare bending- and stretching-dominated structures, two strut-based lattices made of Ti-6Al-4V alloy consisting of the octet and tetrakaidecahedron (or Kelvin) cells are examined. The specimens are designed to fail in the central area of the specimen where edge effects are minimized. Finite element results of the relevant structural mechanics are implemented and exercised to compare the performance of the eight relevant geometries and to evaluate the effect of relative density on fatigue life.

Phase transition of GvpU regulates gas vesicle clustering in bacteria.

Gas vesicles (GVs) are microbial protein organelles that support cellular buoyancy. GV engineering has multiple applications, including reporter gene imaging, acoustic control and payload delivery. GVs often cluster into a honeycomb pattern to minimize occupancy of the cytosol. The underlying molecular mechanism and the influence on cellular physiology remain unknown. Using genetic, biochemical and imaging approaches, here we identify GvpU from Priestia megaterium as a protein that regulates GV clustering in vitro and upon expression in Escherichia coli. GvpU binds to the C-terminal tail of the core GV shell protein and undergoes a phase transition to form clusters in subsaturated solution. These properties of GvpU tune GV clustering and directly modulate bacterial fitness. GV variants can be designed with controllable sensitivity to GvpU-mediated clustering, enabling design of genetically tunable biosensors. Our findings elucidate the molecular mechanisms and functional roles of GV clustering, enabling its programmability for biomedical applications.

Experimental comparisons of speech transmission index prediction methods

Good speech intelligibility is the primary goal of acoustic environment control in lecture rooms and auditoria. The speech transmission index (STI) is the primary objective evaluation metric for speech intelligibility. Therefore, accurate prediction of the STI during the design stage is important for acoustic environment control in lecture rooms and auditoria. Two types of STI prediction methods based on simulated impulse responses and statistical are recommended by the IEC standard. In this study, the prediction accuracy and influencing factors of these two types of prediction methods were systematically analysed using STI measurements collected at 25 receiver positions in six rooms. The results reveal the following. (1) When the influence of the signal-to-noise ratio (SNR) is not considered, for the STI prediction method based on simulated impulse responses, the prediction accuracy is in an acceptable range with the average predicted STI discrepancy of the 25 receiver positions being −0.004 and the maximum discrepancy being 0.046. For the STI prediction method based on statistical, the average predicted STI discrepancy of the 25 receiver positions was −0.015, and the maximum discrepancy was −0.091. STI prediction based on statistical exhibited a larger prediction error at the receiver positions close to the sound source and smaller prediction error at the receiver positions farther away from the sound source. (2) When the influence of the SNR was considered, the errors of both prediction methods increased significantly. For the STI prediction method based on simulated impulse responses, the average predicted STI discrepancy of the 25 receiver positions was −0.035 and the maximum discrepancy was −0.088. For the STI prediction method based on statistical, the average predicted STI discrepancy of the 25 receiver positions was −0.030 and the maximum discrepancy was −0.112. (3) Using a sound source that is different from the onsite measurement sound source can induce noticeable errors in both methods. (4) For the STI prediction method based on statistical using the actual Q value of the sound source, the prediction accuracy of receiver positions close to the sound source can be significantly improved and the effect on receiver positions farther away from the sound source is relatively small. (5) Both methods require significant technical expertise from users, rendering it difficult to obtain accurate prediction results during the design stage.

Sound field of subway platforms with complex forms

While the sound field characteristics of idealised long enclosures have been demonstrated, this study aimed to reveal the sound field of subway platforms with complex forms. The sound fields of ten actual subway platforms with complex forms were simulated, and the sound pressure level (SPL) attenuation and reverberation time (RT 30) were analysed. The results indicated that the average SPL attenuations of actual platforms with complex forms were 3.0 ∼ 7.7 dB greater than that with a corresponding idealised long enclosure, and the average RT 30 was 0.1 ∼ 0.5 s shorter. Regarding the receivers along the length, with the source-receiver distance increasing, the SPL attenuation showed an approximately logarithmic curve, and RT 30 presented a slightly increasing trend. The distance from the centre of each protruding space to the source was linearly correlated to both the average SPL attenuation and average RT 30 in each space. The geometrical parameters of ground perimeter, ground area, and average width were negatively correlated with the average SPL attenuation, and they were not significantly correlated with the average RT 30 for the actual subway platforms with complex forms. These results are expected to provide a reference for the design of underground subway platforms, acoustic environment controls, and soundscapes.

Discrimination and sensorimotor adaptation of self-produced vowels in cochlear implant users.

Humans rely on auditory feedback to monitor and adjust their speech for clarity. Cochlear implants (CIs) have helped over a million people restore access to auditory feedback, which significantly improves speech production. However, there is substantial variability in outcomes. This study investigates the extent to which CI users can use their auditory feedback to detect self-produced sensory errors and make adjustments to their speech, given the coarse spectral resolution provided by their implants. First, we used an auditory discrimination task to assess the sensitivity of CI users to small differences in formant frequencies of their self-produced vowels. Then, CI users produced words with altered auditory feedback in order to assess sensorimotor adaptation to auditory error. Almost half of the CI users tested can detect small, within-channel differences in their self-produced vowels, and they can utilize this auditory feedback towards speech adaptation. An acoustic hearing control group showed better sensitivity to the shifts in vowels, even in CI-simulated speech, and elicited more robust speech adaptation behavior than the CI users. Nevertheless, this study confirms that CI users can compensate for sensory errors in their speech and supports the idea that sensitivity to these errors may relate to variability in production.

An investigation of the effect of randomness in trunk size and location on the attenuation of sound through forests generated by Lindenmayer systems

This presentation provides an overview of what is known about the influence of randomness in trunk size and location on the attenuation of sound through forests. It also provides an explanation of the Lindenmayer system (L-system) approach to modeling plants and trees in addition to the multiset L-system approach to modeling the dynamics of forest ecosystems, investigating its applicability to the problem of optimizing sound attenuation through forests. This project was completed in partial fulfillment of the requirements for the Diploma in Acoustics and Noise Control, Institute of Acoustics, Milton Keynes, UK, under the mentorship of Dr. Keith Attenborough.