Sound Control Research Articles

Study on Electrical Services and Control for Heating, Ventilation and Air-conditioning in Buildings

In modern age of technology, the concept of energy saving and environmental comfort raise the building services and controls as a significant issue during the design, installation, operation and management. Proper electrical services and sound control systems, especially for Heating, Ventilation and Air-conditioning (HVAC) sections, can not only make our lives more convenient and pleasant, but also increase the energy efficiency in the view of sustainable development.

Active noise control at low frequencies for outdoor live music events using the conjugate gradient least square method

Sound field control can be applied to the problem of reducing noise emissions from outdoor live music events. One method employed in this type of applications is pressure matching. Different approaches can be used to find a solution to this problem. Many of these methods can provide reduction of more than 10 dB in the frequency range of a subwoofer, between 30 and 120 Hz, thus reducing the loudness to half the original. Such a performance is adequate, but it comes with drawbacks and/or practical limitations such as side lobes that can create new problems in new areas, computational cost, difficult parameter selection, etc. The method proposed here uses the conjugate gradient least square to compute a solution while providing an easier way to find a suitable regularization and at the same time controlling the radiation pattern of the solution to reduce the possibility of side lobes. In addition, the use of an active set-type methods allows to include explicit constraints on the amplitude of the solution to avoid amplification and non-linear behavior of the transducers. After introducing the theory, the performances are compared to other more established methods through simulations and outdoor measurements performed at a 2:1 scale to show properties and practical aspects of the method proposed. These experiments show that 10 dB insertion loss are achieved over a broad frequency range with peaks larger than 20 dB. We investigate the difference in performance between the different methods and use simulated versus measured transfer functions to derive the filters. We also analyze the numerical properties of the solutions provided by the different methods and relate them to the spatial properties of the corresponding sound fields. Furthermore, we present a convergence study to evaluate the effect that grids of different resolutions used in the simulations have on the insertion loss for different degrees of regularization. Finally, we present also a sensitivity analysis of the proposed method to uncertainties in the speed of sound and show how the regularization directly affects the robustness of the method against such inaccuracies.

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.

Recent Advancements in Topical Anti-Psoriatic Nanostructured Lipid Carrier-Based Drug Delivery.

Psoriasis is linked with unusual differentiation and hyperproliferation of epidermal keratinocytes that significantly impair the quality of life (QoL) of patients. The present treatment options only provide symptomatic relief and are surrounded by various adverse effects. Recently, nanostructured lipid carriers (NLCs) have emerged as next-generation nanocarriers with better physicochemical characteristics. The current manuscript provides background information on psoriasis, its pathophysiology, existing treatment options, and its limitations. It highlights the advantages, rationale, and mechanism of the permeation of NLCs for the treatment of psoriasis. It further gives a detailed account of various NLC nanoformulations for the treatment of psoriasis. In addition, tabular information is provided on the most relevant patents on NLCs for treating psoriasis. Lastly, light is shed on regulatory considerations related to NLC-like nanoformulations. In the treatment of psoriasis, NLCs display a sustained release drug profile, an ability to incorporate both hydrophobic and hydrophilic drugs, an enhancement in skin hydration, penetrability, retention, and bioavailability of the drug, along with reduced staining potential as compared to conventional ointments, and decreased side effects of drug molecules. This affirms the bright future of NLC nanoformulations in the treatment of psoriasis. However, academic industry collaboration and more sound regulatory controls are required to commercialize the NLC nanoformulations for psoriasis treatment.

A review of techniques and challenges in outdoor sound field control

The application of sound field control to outdoor live events at low frequencies is a recent one due to increased concerns regarding noise pollution and stronger regulations. Here is presented an overview of the techniques being recently investigated based on model, data or hybrid approaches. The approaches presented here provide encouraging results but they all deal with the problem at relatively short distances (approximately 100m). Translating these results to larger distances is going to be a challenge as a new set of problems needs to be addressed. An overview of the most relevant issues encoutered in long range applications such as un-even terrain, properties of the medium, ground and obstacles interacions is also presented.

Technical aspects of physical implementation of an active noise control system: challenges and opportunities

Active noise control systems have become a subject of intensive worldwide research that have aroused considerable interest as being a promising solution to the problem of low-frequency noise control. Advanced real-time signal processing technologies offer opportunities that have been adopted in many active noise control industry applications, as well as in the modern urban environment where noise reduction is gaining priority status. Depending on the application, the concept of active sound control can be implemented using different control strategies. The development and application of such systems requires in-depth knowledge and theoretical analysis in the field of digital signal processing, sensor technology, adaptive control, understanding in hardware solutions for acquisition and data processing, as well as software capabilities for modeling, visualization and control of signals. Also, the construction of such a system must give an overview of the choice and characteristics of its components in terms of the impact of the elements that make it up on its accomplishment. This paper provides an insight into the engineering aspects for implementation of an active noise control system in a duct, emphasizing all technical requirements that need to be analyzed and might further affect the systems overall performance.

Vibrational damping properties of finite microperforated plates

Microperforated plates (MPP) are traditionally used to advantageously absorb acoustic waves in sound control technologies. However, less is known concerning the additional structural damping they can induce. The latter is activated through exchanges in the viscous and thermal boundary layers near the fluid-structure interface of the microperforations. MPPs therefore offer an alternative to, or can be used together with, viscoelastic materials, commonly implemented to damp vibrations at medium and high frequencies. In this work, the structural damping capabilities of MPP are investigated. To this end, the damping performance of a finite size MPP is explored analytically through an alternative form of the Biot model, classically devoted to porous plates, and considering energy dissipation through viscous friction mechanisms. Analytical results are compared to experimental measurements of structural damping factors on various MPP samples. The model is validated and confirms the damping effect added by the microperforations in the low frequency range. A sensitivity analysis on the perforation rate and perforation diameter provides a condition for which additional damping is maximized.

Incorporating random effects in biopharmaceutical control strategies

ObjectiveRandom effects are often neglected when defining the control strategy for a biopharmaceutical process. In this article, we present a case study that highlights the importance of considering the variance introduced by random effects in the calculation of proven acceptable ranges (PAR), which form the basis of the control strategy.MethodsLinear mixed models were used to model relations between process parameters and critical quality attributes in a set of unit operations that comprises a typical biopharmaceutical manufacturing process. Fitting such models yields estimates of fixed and random effect sizes as well as random and residual variance components. To form PARs, tolerance intervals specific to mixed models were applied that incorporate the random effect contribution to variance.ResultsWe compared standardized fixed and random effect sizes for each unit operation and CQA. The results show that the investigated random effect is not only significant but in some unit operations even larger than the average fixed effect. A comparison between ordinary least squares and mixed models tolerance intervals shows that neglecting the contribution of the random effect can result in PARs that are too optimistic.ConclusionsUncontrollable effects such as week-to-week variability play a major role in process variability and can be modelled as a random effect. Following a workflow such as the one suggested in this article, random effects can be incorporated into a statistically sound control strategy, leading to lowered out of specification results and reduced patient risk.

Validation of a potential-based active sound control methodology

This paper describes a global active sound control methodology based on difference potentials in a three-dimensional space. The proposed alternative method allows the reduction of a boundary value problem set in a complex domain to a boundary equation. The only input data needed by the methodology are the acoustic quantities at the perimeter of the protected region. By minimizing the number of input data, the characteristics of the method provide a practical and cost-effective control system. Moreover, these quantities may pertain to the overall acoustic field composed of both the unwanted and wanted components. The most distinctive feature of this methodology is its ability to automatically differentiates between the wanted sounds and unwanted noise within targeted domains. The proposed approach requires information of neither the wanted nor unwanted component separately, but the measurements of the total field on the boundaries of the shielded domain only. This capability can be very useful for the applications related to personal audio and building acoustics as it enables protection of the predefined personal space against the noise coming from the outside. In doing so, the controls will not interfere with the detectors' recognition of the wanted sound or communication among speakers in the room.

Monitoring and Automation System of Swiftlet House Using Internet Of Things (IoT) Based

This research aims to make a tool in the form of a technological engineering system that is integrated with its operation so that swiftlet farmers can use it. This research is expected to produce a more effective and efficient technology than partial tools and has not yet answered the needs of swallow farmers. The stages in this study used flowcharts consisting of literature studies, program design, making system blocks, system integration, tool testing, and analysis of the results. The system design consists of determining tools and materials and making a block diagram of the work system of the tool with the ESP32 microcontroller. In system settings, it is divided into several system blocks: sound control system block, temperature and humidity control, window opening and closing control, lighting control and streaming video monitoring in swiftlet houses. Based on the results of the study, it was obtained that monitoring and automation system tools for swallow houses use IoT-based Esp32. This tool can automatically regulate and automate sound, temperature, humidity, lighting, and windows in swiftlet houses and can be monitored remotely.

A metamaterial plate with magnetorheological elastomers and gradient resonators for tuneable, low-frequency and broadband flexural wave manipulation

Incorporating magnetorheological elastomers and multiple gradient resonators (MRE–MGRs), a novel metamaterial plate is proposed, which entails low-frequency, broadband and tuneable bandgap features. The proposed MRE-MGR design embeds an adaptive magnetic field adjustment mechanism to alter the elastic modulus of the MRE to modulate the local resonance bandgap frequency and bandwidth. A bandgap prediction model of the metamaterial plate is developed using the plane wave expansion (PWE) method. Integrated into the model through equivalent stiffness terms, the magneto-controlled modulus of the MRE can be estimated using the energy method and magnetic dipole theory. The established model allows for revealing the dispersion relation of the proposed metamaterial plate under various magnetic fields. The predicted tuneable bandgaps, vibration transmission loss and flexural wave modulation of the metamaterial plate are validated through comparisons with finite element simulations. Numerical analyses show the benefit of the gradient resonator design, which alongside the effective MRE tuning, entails broadening low frequency bandgaps at 92 Hz (relative band of 79.3% for the exponential gradient) and 72.7 Hz (relative band of 65.9% for the linear gradient). The mechanisms underpinning the observed bandgap widening phenomenon are analysed and attributed to the combined effects arising from the gradient design of the distributed resonators and the effective tuning of the MRE elastic modulus under magnetic field modulation. The proposed metamaterial plate functionally achieves simultaneous magnetron adjustment of the bandgap frequency and its width, thus holding great promise for applications such as flexural wave guiding as well as vibration and sound radiation control in planar structures.

Origami-based tunable mechanical memory metamaterial for vibration attenuation

Tunable metamaterials without the necessity to redesign parameters and remanufacture have received increasing interest in recent years due to their rich dynamic characteristics and wide potential applications in vibration and sound control. In this work, we propose and analyze a mechanical memory metamaterial with tunability based on the Kresling origami that can easily be reconfigured for vibration attenuation in a desired frequency range. Unlike previous Kresling origami metamaterials in which rotational motion is transferred along the origami chain, rotations are localized in the proposed tunable metamaterial, which avoids introducing rotations between the ends of the metamaterial. The static and dynamic characteristics of the metamaterial are theoretically analyzed based on the truss model of the origami. By utilizing the bi-stability of the Kresling origami module (KOM) with asymmetric stiffness, the metamaterial can achieve rich dynamic behaviour with various memories. Each memory represents a pattern of periodic repeating cells in the metamaterial by switching the stable states of KOMs. The transmissibility and bandgaps of the metamaterial are determined analytically and verified by numerical simulations. The results demonstrate the tunability of the proposed metamaterial by switching its memories. Besides, the parametric study shows that the bandgap frequency ranges of the metamaterial can be expanded by adjusting the mass moment of inertia of the KOMs’ middle planes, making the antiresonance frequency of the system close to one of its natural frequencies and/or introducing damping. Finally, the proposed Kresling origami metamaterial is implemented and tested, and the tunability of vibration attenuation by memory switching of the proposed origami metamaterial is demonstrated. The proposed origami-based mechanical memory metamaterial will promote the development of dynamics and vibration control technology and advanced mechanical metamaterials.

Signal-to-Interference-Plus-Noise Ratio Based Optimization for Sound Zone Control

Sound zone control is posed as an optimization problem where finite impulse response control filters are jointly optimized for low transmit power, while maintaining a sufficiently high signal-to-interference-plus-noise ratio (SINR) in all zones. This problem statement in particular allows the consideration of sound zone control under the additional influence of external noise, which is rarely taken into account and indeed necessitates an alternative problem statement. In addition, the spectral characteristics of the audio signals are taken into account, both for the transmit power minimization and computing the SINR. The optimization problem is shown to be solved optimally by semidefinite relaxation, but the computational cost is high. An alternate method is proposed, inspired by a duality between transmit and receive beamforming commonly exploited in digital communications. A virtual receive optimization problem for sound zone control is derived, and it is shown to have the same optimal solution as the original transmit optimization problem. The receive optimization problem is solved efficiently through a fixed point iteration algorithm. The two proposed methods are compared against acoustic contrast controlin a simulated reverberant environment, where it is shown that the proposed methods require less transmit power to produce similar SINRs.

Amplitude Matching for Multizone Sound Field Control

A multizone sound field control method, called amplitude matching, is proposed. The objective of amplitude matching is to synthesize a desired amplitude (or magnitude) distribution over a target region with multiple loudspeakers, whereas the phase distribution is arbitrary. Most of the current multizone sound field control methods are intended to synthesize a specific sound field including phase or to control acoustic potential energy inside the target region. In amplitude matching, a specific desired amplitude distribution can be set, ignoring sound propagation directions. Although the optimization problem of amplitude matching does not have a closed-form solution, our proposed algorithm based on the alternating direction method of multipliers (ADMM) allows us to accurately and efficiently synthesize the desired amplitude distribution. We also introduce the differential-norm penalty for a time-domain filter design with a small filter length. The experimental results indicated that the proposed method outperforms current multizone sound field control methods in terms of accuracy of the synthesized amplitude distribution.

Fraud Detection and Forensic Accounting in listed Manufacturing Firms in Nigeria

This study examines fraud detection and forensic accounting in listed manufacturing firms in Nigeria. Ordinary regressions analysis was used for the analysis of the data and pre-estimation tests were carried out. Data were obtained from the structured questionnaire. The findings of this study showed that all the explanatory variables (ICS, AC and WB) have significant positive relationships with dependent variable (FA) The study concluded that there is significant positive relationship between fraud detection and forensic accounting in listed manufacturing firms in Nigeria and recommends that management of manufacturing firms should establish sound internal controls system, effective audit committee and put in place whistle blowing mechanisms.

Violência sonora em viagens de ônibus

Abstract The article focuses on the recurring and conflicting case of musical performance on public transport, analyzing the forced musical experience as an act of violence entangled with several other forms of violence. It discusses how fear conditions the listening of musical experience in urban environments, shaped by shared values, ideas, and prejudices about music that is spread in public transport. The imposition of a certain musical repertoire on other passengers is configured as a political action that claims to be heard by individuals who suffer different types of oppression. However, at the same time, it contributes to the sedimentation of stigmatization reinforced by forced listening. Informed by interviews in Rio de Janeiro, the text seeks to deepen the debate on the uses of music in public spaces, incorporating the complexities and contradictions that permeate sound and musical control in public transport in Latin American metropolises.

Audio Management: Enhancing Wireless Sound Control through Hand Gestures

This research paper presents research conducted to control the sound level of the system using hand gestures. The proposed system is designed using Python programming language and OpenCV library. The development of programs that can be controlled using natural gestures is an important area of research in the field of human-computer interaction. The system captures the video feed from the camera and analyzes it to detect the hand gestures. The captured frames are preprocessed to remove noise and simplify processing. The image is then converted to grayscale, thresholded to separate the hand from the background, and contours are found in the thresholded image. The detected gestures are then mapped to control the sound level of the system. The proposed system is implemented and tested on a laptop computer with satisfactory results. The program is tested on a range of operating systems and environments to ensure compatibility and functionality. To optimize for speed and efficiency, the program can be parallelized and/or implemented using GPU acceleration.

CHALLENGES AND PROSPECTS OF FINANCIAL MANAGEMENT IN LOCAL GOVERNMENT COUNCILS IN NIGERIA

Globally, government pursued various form of public Financial Management (FM) reforms to
 enhance Local Government (LG) performance. A poor FM has contributed to the failure and inefficiency of LG in achieving substantial development, while most LG faces the problems of wide gap between citizens’ needs and the financial resources. It is against this background that the study examined FM in LG with a view to determining its contribution to the economy, efficiency and effectiveness of LG administration. The study employed an exploratory research design with focus on relevant literatures. The study concluded that LG administrators should act in the same manner as their counterparts in the private sectors based on modern FM practices, this will increase efficiency, financial capability, transparency and accountability in goods and services delivery. In addition, a sound internal control system should be put in place to minimise the level of fraud, corruptions and wastages affecting LG. Besides, LG should always prepare accurate and reliable annual budget, while financial planning and control should be seen as an important aspect of an effective FM.

Determination of shear behavior of magneto-rheological elastomers under harmonic loading

Magneto-rheological (MR) materials can respond reversibly and quickly under the effect of an external magnetic field. MR materials contain micron-sized iron particles. These iron particles are typically dispersed in an elastomer or a liquid. These materials due to their properties constitute a kind of smart material in terms of engineering material. Such materials are used as isolators in various engineering applications, structures, and sound control subsystems. This study aimed to determine the mechanical properties for shear behavior of MR materials for under harmonic loading. Parameters such as matrix materials with different hardness values, powder types, magnetic field, frequency, and deformation were studied. The parameters related to the MR material itself were analyzed with the obtained data. The present study reveals that considering the sensitivity to magnetic field parameter, composite materials having the most suitable properties were produced with Shore 2 hardness value and SQ magnetic powder. It had been observed on increase about 200% at the rate of Shore A10 and A2 as a result of comparing the hardness scale. Also according to the powder rate while there was an increase on worth effect of relative MR, it is seen that the biggest increase had been in SQ powder with 199% worth. When looked some studies in literature, about comparing different hardness values such as matrix materials powder types etc. there aren’t any studies. The state of magnetic field thinks that features such as MR effect, Storage, and Loss modulus haven’t been examined yet.

Multifunctional acoustic metamaterial for air ventilation, broadband sound insulation and switchable transmission

Noise reduction and other manipulation of sound waves has been a major concern in science and engineering. Here, we propose a ventilated soundproof acoustic metamaterial consisting of resonant cavities arranged around a central air passage. This metamaterial can accomplish strong sound insulation performance. The transmission loss is larger than 30 dB within a wide frequency range (625–1695 Hz) due to the prohibited band. More intriguingly, we discover that rotating the opening, somewhat like an acoustic switch, can directly control the sound transmission of the deaf band. This is particularly useful for opening a narrow but high transmission window at the frequency of interest, which provides a new degree of freedom for sound control. Through band structure analysis and effective parameter calculation, we discover the sound insulation mechanism of the ventilated metamaterial and reveal the underlying mechanism of the switchable narrow-band sound transmission. Beyond the 1D study, the proposed acoustic metamaterial is expanded to a 3D soundproof metacage. We find that the sound insulation performance and switchable sound transmission phenomena are still retained for the metacage. The results reported here may inspire more exploration of sound barriers and multifunctional applications, such as innovative building facades for noise reduction and logic components for acoustic circuits.