Design of Ultra low noise cooling tower and air cooled Generator

Active noise control (ANC) effectively reduces tonal noise in industrial ducts, particularly at low frequencies, which is crucial for maintaining a safe and compliant working environment. However, traditional algorithms, such as filtered-x least mean squares (FXLMS), struggle to handle well-known operational constraints, including actuator saturations. Conversely, model predictive control (MPC) effectively manages these constraints but encounters computational challenges, particularly in fast dynamic systems like ANC. This study presents an innovative MPC framework that explicitly addresses operational constraints while ensuring effective noise attenuation. Unlike conventional MPC applications, which treat primary noise as a disturbance in ANC, our framework utilizes primary path modeling to estimate future reference values, thereby enhancing control performance in this fast dynamic system. The methodology is validated through numerical experiments, utilizing identified primary and secondary path models in an active noise control test setup. Results demonstrate the proposed MPC framework’s practical feasibility and significant performance advantages over traditional FXLMS methods, including improved noise attenuation and robust handling of operational constraints.

<sec>Fluid-structure interaction pipeline systems are extensively adopted to transfer matter, energy and momentum, which are widely used in various fields. Due to the fluid-structure interaction effect, the pipe wall proves to produce strong vibration and noise under fluid action, which has a serious influence on the safety and concealment of the equipment, even leading to serious damages. Therefore, it is of great significance to study the vibration characteristics of fluid-structure interaction pipeline and methods to reduce the vibration of pipeline both in theory and in practice. </sec><sec>Phononic crystal can suppress the propagation of elastic waves in a specific frequency range by their special band-gap characteristics, which have wide application prospects in the field of vibration and noise reduction. Especially, the band gap characteristics of phononic crystal pipeline used to design fluid-structure interaction pipeline system have been widely studied, thus providing a new technical approach to reducing the vibration and noise of the pipeline. </sec><sec>In this paper, based on the theory of phononic crystal, the vibration transfer characteristics of the Bragg phononic crystal pipeline under fluid-structure interaction are studied. Combining the transfer matrix method and the finite element method, the band structure and band gap characteristics are calculated. Using the finite element method, the vibration characteristics of the phononic crystal pipeline under fluid-structure interaction effect, the shock excitation of pipe wall and the shock excitation of the fluid are considered. The influence of the fluid-structure interaction on the vibration transmission characteristics of the phononic crystal pipeline is also analyzed. </sec><sec>The research results indicate that when the fluid velocity in the fluid-structure interaction pipeline system is small the Bragg phononic crystal pipeline has a good attenuation effect on the shock excitation of pipe wall in the band gap range, and that when the fluid velocity increases the fluid-structure interaction effect becomes significant, the attenuation effect becoming weaker. Bragg phononic crystal pipeline has a certain attenuation effect on the pipe wall vibration caused by the fluid shock excitation near the band gap. The research results are expected to be able to provide a technical reference for the vibration control of pipeline systems under fluid-structure interaction conditions. </sec>

PreviousNext No AccessSEG Technical Program Expanded Abstracts 2010Noise attenuation methods for point‐receiver land seismic dataAuthors: Ying JiEd KraghClaudio BagainiYing JiSchlumberger Cambridge ResearchSearch for more papers by this author, Ed KraghSchlumberger Cambridge ResearchSearch for more papers by this author, and Claudio BagainiSchlumberger Cambridge ResearchSearch for more papers by this authorhttps://doi.org/10.1190/1.3513586 SectionsAboutPDF/ePub ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinked InRedditEmail Abstract Data quality from onshore seismic acquisition can be challenging because of near‐surface complexity combined with the high amplitude of source‐generated noise. The very large channel count of modern acquisition systems enables sampling the source‐generated noise. In this paper, we focus on one of the very first processing steps, attenuating the source‐generated noise by digitizing the signal recorded by every individual sensor: point‐receiver data. We outline the principles of three algorithms for noise attenuation in point‐receiver data and we apply them to two onshore datasets acquired in very different conditions: permafrost and desert. The data examples clearly demonstrate the effectiveness of the coherent noise attenuation combined with excellent signal preservation.Permalink: https://doi.org/10.1190/1.3513586FiguresReferencesRelatedDetailsCited ByNonlinear beamforming for enhancement of 3D prestack land seismic dataAndrey Bakulin, Ilya Silvestrov, Maxim Dmitriev, Dmitry Neklyudov, Maxim Protasov, Kirill Gadylshin, and Victor Dolgov31 March 2020 | GEOPHYSICS, Vol. 85, No. 3 SEG Technical Program Expanded Abstracts 2010ISSN (print):1052-3812 ISSN (online):1949-4645Copyright: 2010 Pages: 4453 publication data© 2010 Copyright © 2010 Society of Exploration GeophysicistsPublisher:Society of Exploration Geophysicists HistoryPublished: 21 Oct 2010 CITATION INFORMATION Ying Ji, Ed Kragh, and Claudio Bagaini, (2010), "Noise attenuation methods for point‐receiver land seismic data," SEG Technical Program Expanded Abstracts : 3545-3549. https://doi.org/10.1190/1.3513586 Plain-Language Summary PDF DownloadLoading ...

Fault seismic attribute volumes (such as volumetric coherence and curvature) represent an efficient and objective way to visualize and identify faults in seismic cubes. Fault geometric attributes such as length, height, and fault segmentation can be extracted from such fault seismic attribute volumes. We evaluate the strengths and pitfalls of using coherence volumes for characterization of fault geometry. The results are obtained using a database from the Barents Sea, which contains 35 3D seismic cubes, together with conceptual synthetic seismic models. A high signal-to-noise ratio is a requirement for the extraction of accurate fault geometric data. Noise attenuation methods improve fault visualization, but our results indicate that the effect of noise attenuation on the extracted fault geometric attributes is only clear in areas of low signal-to-noise ratios. The choice of coherence algorithm is important when extracting fault length data. Semblance-based coherence performs better than gradient structure tensor-based coherence in low-displacement areas near the fault tips, and it produces more accurate fault length data. Faults can appear segmented in coherence volumes if relatively similar reflectors are juxtaposed across a fault. In such areas, it is important that the interpreter does not overlook the fault. The size of the analysis window used in coherence calculations controls the resolution and continuity of the imaged faults. Our results support an optimal temporal window size of one to two times the dominant period of the seismic data (typically 7–17 samples in conventional 4 ms sampled 3D seismic data). Larger temporal window sizes can result in an overestimation of fault height, especially for small faults. A large spatial window can smear out segmentation along the fault and make the fault traces wider. Even though a large spatial window can have some positive effects, we recommend using a relatively small spatial window (five traces) when extracting subtle fault geometric attributes.

This paper describes the effect of excess attenuation of conventional railway noise due to detached houses. The excess attenuation due to detached houses were estimated by using both ASJ RTN-Model 2013, which is generally used for road traffic noise, and the noise prediction model of conventional railway. It is found that the overall trends are well-predicted in both the case of the level section and the viaduct section. In the case of the level section, slightly worse agreement is found at some points. This is due to the influence on acoustic reflection on the house behind the predicted point and the screening effect of houses. In the case of the viaduct section, agreement is poorer. This is because the effect of sound propagated over houses is not included in the ASJ model.

Environmental noise pollution (30-8000 Hz, 50-90 dB) has become a central health concern due to its impact on human psychology and physiology. Acoustically, aesthetic architecture has recently been explored for noise control, where sonic crystals (SCs) offer both effective sound attenuation and seamless architectural integration. However, conventional SCs with circular scatterers remain limited in suppressing low-frequency noise because Bragg scattering requires lattice constants comparable to the acoustic wavelength, making large structures impractical for subwavelength regimes. Herein, we propose a Hexa-resonator SC, optimized, simulated, and experimentally validated for its noise attenuation performance. With band structure calculations and eigenfrequency mode analysis, the insertion loss (IL) was investigated over 20-1000 Hz. In the sub-kilohertz region, the SC exhibited two first-order resonance peaks around 150 and 200 Hz and a first-order Bragg band (255-410 Hz). It showed a maximum IL of approximately 36 dB at 303 Hz (in the Bragg region), confirming its effectiveness for low-frequency noise attenuation. The influence of cavity geometry on phase pressure variations and IL was analyzed, revealing hybridization and mode coupling effects. Experiments qualitatively follow the simulated trends.

To prevent SARS-CoV-2 transmission in designated quarantine hotel for travelers: Is the ventilation system a concern?

The prediction of upstream noise generated by aeroengine components including acoustic liners under realistic flight conditions is an important tool for the aircraft design process. In general, the acoustic absorbing properties of liners and the resulting noise mitigation are affected by the presence of the boundary layer. The main goal of this study is to compare the effect of liner attenuation in the far field for different boundary conditions representing the liners, including uniform and shear flows, and consider typical turbofan geometry and operating conditions. For uniform flow cases, a reference solution was obtained from a finite element method code and used to validate the analytical model, which is based on the in-duct mode-matching technique and an analytic radiation model. For shear flow cases, the Brambley boundary condition and the solution to the Pridmore–Brown equation were considered; and the power transmission and modal decay rate along the duct were compared for increasing boundary-layer thickness. The transmitted modes were coupled to the radiation model based on the Kirchhoff integral approximation. The results suggest that the influence of the boundary-layer thickness can lead to a significant reduction on liner attenuation in some conditions. Moreover, it was observed in some cases that modal scattering produced by liner discontinuities results in a complex behavior (with the redistribution of the acoustic energy onto cut-on modes) in terms of noise radiation.

Recently, active noise control technology has been used to increase the sound transmission loss of double-wall structures. Several approaches have been put forward and explored individually. However, no comparative study on those approaches has been conducted to show which approach is more effective for given circumstances. In this paper, three different approaches for controlling sound transmission through double-panel partitions into a room, i.e., applying acoustic control sources in the air gap between the two panels (cavity control), applying vibration control sources on the radiating panel (panel control), and applying acoustic control sources in the receiving room (room control), are studied and compared to each other experimentally. The mechanisms involved in each approach are illustrated and the conditions for effective noise attenuation are examined. The results show that the modal overlap of each subsystem (the cavity, the radiating panel, and the room) and the control mechanisms involved are the two most important factors that determine the effectiveness of each corresponding approach.

Seafloor seismic acquisition systems, such as ocean-bottom node (OBN) and cable (OBC) arrays, provide multi-component data essential for high-resolution imaging. Among them, vertical geophone recordings are often contaminated by shear-type noise (known as Vz noise), which arises from near-surface scattering and poor sensor coupling. This noise appears as incoherent energy in common shot gathers (CSGs) and as coherent hyperbolic events in common receiver gathers (CRGs), reducing data quality. We present a hybrid Radon transform-based method for attenuating shear noise in seafloor vertical geophone data. By combining linear and hyperbolic Radon transforms, the method enables effective separation of signal and noise. Two approaches are explored: (1) a geophone-only denoising in the CSG domain that reduces random noise and indirectly suppresses coherent noise in CRGs, and (2) a joint sparsity recovery method that incorporates hydrophone data as a reference to remove coherent noise in CRGs. Results on the Equinor Volve OBC dataset demonstrate effective noise attenuation and signal preservation, offering a practical solution for denoising multi-component seafloor seismic data.

Summary Random noise is unavoidable in seismic exploration especially in complex surface and deep exploration environments. With development of full-azimuth high-density acquisition, random noise attenuation is to deal with the nonstationary characteristics while handling the large-scale data with limited computational cost. In this paper, we propose a new f -x-y adaptive prediction filter to attenuate random noise based on the streaming framework. Instead of using iterative optimization algorithm, we directly derive the analytical solution for the overdetermined least-squares problem in the frequency domain and use snaky processing order to improve the effectiveness of prediction filter. Numerical experiments show that the 3D f -x-y streaming prediction filter (SPF) is suitable for large-scale seismic data with the advantages of low computational cost, reasonable nonstationary signal protection, and effective random noise attenuation.

Three active noise control (ANC) systems, which incorporates different arrangements of the secondary loudspeaker, have been examined experimentally, based on the analysis of the characteristics of sound wave propagation in a duct. Measured transfer functions of the plant and the error paths show good agreement with the theoretically derived transfer functions in the acoustic modal frequencies of the systems. Real-time experiments showed a more effective noise attenuation with a tree-shaped configuration than with the traditional T-shaped ANC system. The symmetric arrangement of two secondary speakers in the tree-shaped system helps in compensating the node observed at 200 Hz in the error path. This compensation can also be achieved by using an equalizer.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The tunable acoustic properties are possessed by acoustic metamaterials (AMMs) with internal configurable structures. Nine samples(B1-B9) were designed in SOLIDWORKS and then fabricated using 3D-printed photopolymer resin featuring an internal Simple Expansion Chamber (SEC) structure. SEC length varied from 2 to 18 mm, maintaining a constant area expansion ratio (m) of 16. Sound Absorption Coefficient (SAC) and Sound Transmission Loss (STL) were measured through the Impedance Tube Apparatus (ITA). The sample with a 4 mm SEC length exhibited a maximum SAC of 0.99 at 4.8 kHz. As SEC length increased peak SAC and peak absorption frequency linearly decreased. Across all samples, STL ranged from 1- 41 dB (0.5-2.4 kHz) and 20-36 dB (2.4-6 kHz) revealing a periodic pattern in the tested frequency range. With SEC increasing from 2 to 18 mm Peak STL decreased from 41.2 to 38.8 dB. This research contributes valuable insights into the design of acoustic materials for effective noise attenuation showcasing the potential for achieving at least a 20 dB reduction in the 2.4-6 kHz range.

Traffic noise transmission through the open windows of naturally-ventilated classrooms can reduce speech intelligibility and can negatively impact academic performance. The findings of a numerical study are presented. Software was used to assess effective noise attenuation solutions for naturally-ventilated classrooms exposed to traffic noise. A typical situation in urban schools in Gauteng, South Africa, is considered in which classrooms are ventilated by large open windows in accordance with national building regulations and norms and standards for school design. The aim of the study was to establish a heuristic framework for early design decisions regarding how far from the road a classroom building should be set, and the effective height and position of a solid noise barrier to ensure a suitable ambient noise level inside a classroom with open windows. Efficacy was measured with reference to an indoor ambient sound level of 40 dBA. The findings show that with the insertion of barriers, the required ambient level was achieved for a classroom at least 68 m from the road, if the barrier is at least 3.5 m high. However, it was found that a significant insertion loss (&gt;6 dB) and an improved signal to noise ratio could be achieved for classrooms as close as 17 m from the road with a barrier of at least 2 m high. Though not broadly generalizable, the findings provide a heuristic guide applicable for designing new schools or selecting attenuation interventions in existing city schools that are similar to those used in the study.

In the search for more effective noise attenuation methods, a number of candidate materials for road noise barriers and partition walls were tested at the Cooper Union Acoustics Research Center in a specially constructed enclosure divided into two sections by a wall constructed of these materials. The transmission losses of cinder blocks filled with various recycled materials constitute the acoustical property of principal interest. Three tests were executed for each type of material: (1) transmission loss measurements; (2) absorption coefficient measurements; and (3) diffraction effects. The intended applications of the designed materials are as noise barriers for urban highways and subway stations, and as partition walls for factories, classrooms, libraries, etc. Recycled materials experimented with would normally end up in land fills or incinerators. [See NOISE-CON Proceedings for full paper.]