Total Noise Reduction Research Articles

Ecological Motorcycle Taxi, incorporation of an electrolyzer as an alternative for the suppression of pollutants and noise reduction

Environmental pollution from transportation has been a fundamental challenge for humanity throughout history, with conventional fuels contributing significantly to environmental degradation. This project seeks to suppress pollution and reduce noise generated by motorcycle taxis, whether for personal and/or private use. The main objective of the research work was to implement an electrolyzer in the combustion system of a motorcycle taxi to suppress environmental pollution and reduce noise. Methods included vehicle preparation, electrolyzer installation, battery adjustment, hydrogen generation, emissions measurement, safety, and data collection. As a result, the electrolyzer was implemented in the single-cylinder motorcycle taxi; The noise limit allowed at work in Peru is 85 dB, which is equivalent to 100 % noise at most; When using gasoline, a value of 76.4 dB was obtained, equivalent to 89.88 % noise, and when using hydrogen, a value of 71.7 dB was obtained, equivalent to 84.35 % noise, therefore, the total noise reduction was 4.70 dB (5.53 %) than established. The discussion highlighted that hydrogen is a clean fuel, with zero emissions and only emitting water vapor instead of polluting gases [5]. The conclusion highlights the critical importance of the research, supported by the total reduction of 5.53 % of noise with this new technology and in turn external sources support that using hydrogen produced a smoother and quieter combustion; Regarding the useful life of the engine, due to the cleaner and more efficient combustion, the accumulation of waste was reduced, which benefits reducing the wear of internal components and the need for costly maintenance.

Experimental investigation into the acoustical superiority of ogee serrations in reducing leading edge noise

An experiment is conducted to study the leading-edge noise reduction characteristics of ogee serrations and their performance compared to conventional serrations under various operating conditions in an aeroacoustic wind tunnel. Both the acoustic source contours and far-field noise spectra are examined. It is shown that ogee serrations are superior to the conventional sawtooth serrations within the entire frequency range of interest under all the Reynolds numbers tested in the experiment. It is found that the noise from the turbulence grid used to generate the required inflow turbulence becomes important when the frequency is close to and above 2 kHz, and therefore must be excluded in the examination of the leading-edge noise spectra. In addition to their effect on turbulence interaction noise, it is shown that the use of ogee serrations may result in weaker trailing-edge noise than that of sawtooth serrations at certain frequencies. The additional noise reduction due to the use of ogee serrations generally increases as λ, the wavelength of the serration, decreases. Furthermore, like sawtooth serrations, the total noise reduction also increases as the λ decreases. Narrow ogee serrations therefore prove to be more desirable when used for reducing leading-edge noise.

THE EFFECT OF USING MULTI LAYER MATERIAL ON DIESEL ENGINE SOUND ABSORBER CASE

Indonesia as a maritime and archipelagic country, makes ships the only option for people to travel outside their territory to meet their daily needs. Ship routes that operate are usually from morning to evening with an average sailing time of 2-3 hours each way where these ships are generally small in size so that the engine and passengers seem to be in the same room. As a result, like it or not, the noise generated by engine noise cannot be avoided and the noise that arises will certainly greatly affect people's health if this noise exceeds a predetermined threshold value if it occurs continuously for a long time. The threshold value (NAV) of noise (caused by engine noise etc.) has been determined by local standards, namely the Regulation of the Minister of Manpower and Transmigration Number PER.13/MEN/X/2011 concerning Threshold Values ​​for Physical and Chemical Factors in the Workplace and The Indonesian National Standard (SNI 16-7063-2004) concerning the Threshold Value of Noise and IMO Resolution of 85 decibel A (dBA). Based on the provisions above, an experiment was carried out to make Diesel engine casing from Plywood and Polyurethane and Glasswool capable of meeting the standards with an average total noise reduction of 5.5 dBA from before but an average temperature increases of 2.3 0C.

Quantitative evaluation of total variation noise reduction algorithm in CT images using 3D-printed customized phantom for femur diagnosis

Quantitative evaluation of total variation noise reduction algorithm in CT images using 3D-printed customized phantom for femur diagnosis

Feasibility of Total Variation Noise Reduction Algorithm According to Various MR-Based PET Images in a Simultaneous PET/MR System: A Phantom Study.

Recently, the total variation (TV) algorithm has been used for noise reduction distribution in degraded nuclear medicine images. To acquire positron emission tomography (PET) to correct the attenuation region in the PET/magnetic resonance (MR) system, the MR Dixon pulse sequence, which is based on controlled aliasing in parallel imaging, results from higher acceleration (CAIPI; MR-ACDixon-CAIPI) and generalized autocalibrating partially parallel acquisition (GRAPPA; MR-ACDixon-GRAPPA) algorithms are used. Therefore, this study aimed to evaluate the image performance of the TV noise reduction algorithm for PET/MR images using the Jaszczak phantom by injecting 18F radioisotopes with PET/MR, which is called mMR (Siemens, Germany), compared with conventional noise-reduction techniques such as Wiener and median filters. The contrast-to-noise (CNR) and coefficient of variation (COV) were used for quantitative analysis. Based on the results, PET images with the TV algorithm were improved by approximately 7.6% for CNR and decreased by approximately 20.0% for COV compared with conventional noise-reduction techniques. In particular, the image quality for the MR-ACDixon-CAIPI PET image was better than that of the MR-ACDixon-GRAPPA PET image. In conclusion, the TV noise-reduction algorithm is efficient for improving the PET image quality in PET/MR systems.

Applicability of Aeroacoustic Scaling Laws of Leading Edge Serrations for Rotating Applications

The dominant aeroacoustic mechanisms of serrated leading edges, subjected to highly turbulent inflow conditions, can be compressed to spanwise decorrelation effects as well as effects of destructive interference. For single aerofoils, the resulting broadband noise reduction is known to follow spectral scaling laws. However, transferring serrated leading edges to rotating machinery, results in noise radiation patterns of significantly increased complexity, impeding to allocate the observed noise reduction to the underlying physical mechanisms. The current study aims at concatenating the scaling laws for stationary aerofoil and rotating-blade application and thus at providing valuable information on the aeroacoustic transferability of leading edge serrations. For the pursued approach, low-pressure axial fans are designed, obtaining identical serrated fan blade geometries than previously analyzed single aerofoils, hence allowing for direct comparison. Highly similar spectral noise reduction patterns are obtained for the broadband noise reduction of the serrated rotors, generally confirming the transferability and showing a scaling with the geometrical parameters of the serrations as well as the inflow conditions. Continuative analysis of the total noise reduction, however, constrains the applicability of the scaling laws to a specific operating range of the rotors and motivates for a devaluation of the scaling coefficients regarding additional rotor-specific effects.

Total Variation-Based Noise Reduction Image Processing Algorithm for Confocal Laser Scanning Microscopy Applied to Activity Assessment of Early Carious Lesions

The confocal laser scanning microscopy (CLSM) system has been widely used to analyze early carious lesions with fluorescent ligands in dental imaging. This system can be used to examine the physiological condition of cellular colonization in the tooth structure. However, the undesirable noise in CLSM images hinders accurate activity assessment of early carious lesions. To address this limitation, a total variation (TV)-based noise reduction algorithm with good edge preservation was developed, and its applicability to medical tooth specimen images obtained with CLSM was verified. To evaluate the imaging performance, the proposed algorithm was compared with conventional filtering methods in terms of the normalized noise power spectrum, contrast-to-noise ratio, and coefficient of variation. The results indicate that the proposed algorithm achieved better noise performance and fine-detail preservation, in comparison with the conventional methods.

Total variation noise reduction algorithm in computed tomography image with custom-built phantom using 3D-printer

Noise in computed tomography (CT) is unavoidable because of various factors such as patient-source-related errors, hardware error, and electrical interference, which lead to unwanted diagnosis errors. Therefore, to solve this problem, we model a noise reduction algorithm based on total variation (TV) and applied it to images acquired using simulation study and 3D printing technology. Moreover, the conventional noise reduction algorithms are applied to the same image for comparative evaluation. For quantitative evaluation of the algorithms, we use the parameters of the coefficient of variation, signal-to-noise ratio, contrast-to-noise ratio, and normalized noise power spectrum. Our results indicate that the proposed TV noise reduction algorithm affords greater improvement in all the evaluation parameters considered in the simulation and 3D-printed phantom study, over the conventional noise reduction algorithms. In conclusion, we believe that our approach can significantly contribute to CT study and application.

Performance Evaluation of New Nonlocal Total Variation Noise Reduction Algorithm in Parallel Magnetic Resonance Imaging with Sensitivity Encoding Reconstruction

Parallel magnetic resonance imaging (pMRI) can acquire high temporal resolution to obtain anatomical images. Among the parallel-imaging techniques, sensitivity encoding (SENSE) is the most widely used. During the SENSE process, they are previously limited by signal-to-noise ratio degradation and aliasing artifacts owing to the subsampling effect. Therefore, the objective of this study was to develop and evaluate a novel nonlocal total variation (new-NLTV) noise reduction algorithm in pMRI with SENSE reconstruction in both simulation and experiments. According to the results, the proposed algorithm was able to achieve impressive results using quantitative evaluation factors in simulation and real phantom images. The contrast-to-noise ratio and coefficient of variation for the algorithm, in particular, were 8.24 and 7.15 times better, respectively, than those of the noisy image in the phantom study. In conclusion, this study successfully demonstrated the effectiveness of the new-NLTV noise reduction algorithm in pMRI with SENSE reconstruction.

Development of a total variation noise reduction algorithm for chest digital tomosynthesis

Chest digital tomosynthesis (CDT) is developed to solve the problem of overlapping and absence of depth information as seen in general X-rays applied in chest radiography and high-exposure dose problem of computed tomography. However, in CDT, noise can reduce the quality of the image and increase the rate of false diagnosis. Thus, noise removal is an important issue in the clinical application of CDT, and a total variation (TV)-based noise reduction algorithm is an excellent algorithm because of its high noise reduction efficiency. In this study, we demonstrate the superiority of the TV noise reduction algorithm by quantitative comparisons of analyses with conventional algorithms. The quantitative evaluation of the image quality, coefficient of variation (COV), contrast-to-noise ratio (CNR), and intensity profile are evaluated. The COV and CNR results in the TV noise reduction algorithm are 1.88 times lower and 1.54 times higher than those of the original image, respectively; the smoothest graph is also obtained in the intensity profile. In conclusion, it is expected that the quality of the CDT image processed using the TV noise reduction algorithm is better than that processed using conventional noise reduction methods and the use of our algorithm will increase in the clinical field in the future.

Preliminary study of total variation noise reduction algorithm with high-energy industrial X-ray imaging system in nondestructive testing field

Abstract Over the past years, many studies have evaluated the performance of nondestructive testing high-energy X-ray imaging methods. In these high-energy industrial X-ray imaging systems, the noise is very important when accurately assessing the nondestructive analysis of faults inside the object volume. A common way to improve the noise performance is the total variation (TV) noise reduction algorithm. Thus, the purpose of this study is to establish a high-energy industrial X-ray imaging system using 450 kVp energy and to confirm the feasibility of our designed TV noise reduction algorithm. We used an X-ray generator (including source, power supply, and cooler) and a flat panel detector made of an amorphous silicon material. In addition, we acquired the X-ray image for a battery and an air pump and then applied our designed TV noise reduction algorithm to these images. To evaluate the image performance, we used normalized noise power spectrum (NNPS), contrast to noise ratio (CNR), and coefficient of variation (COV). According to the NNPS result, the noise performance of our method was improved compared to conventional noise reduction methods. In addition, the CNR of our TV noise reduction algorithm was 1.58, 1.30, and 1.26 times greater than that achieved for the noisy image, median filter and Wiener filter, respectively. We also acquired excellent COV results for the high-energy X-ray imaging system (about 1.93 times higher than that of the noisy image). Our results suggest that a TV noise reduction algorithm can be constructed with an improved image performance in high-energy industrial X-ray imaging systems.

Research on the technology of noise reduction in hybrid electric vehicle with composite materials

The noise source of hybrid electric vehicle is varied, which makes the frequency band from low-frequency to high-frequency distribution. Using a single material to control the hybrid electric vehicle interior noise to improve the performance of vehicle, noise, vibration, and harshness performance is limited. In this article, the composite noise reduction materials which have the function of damping and acoustic absorption are used to control the vehicle interior noise. First, the noise characteristics of the hybrid electric vehicle are analyzed. The distribution of the hybrid electric vehicle interior noise is obtained. Then, the sound-absorbing properties of polyester-polypropylene bi-component fiber are analyzed. The low-frequency noise reduction principle of butyl rubber damping material is also analyzed. Finally, the noise reduction materials consisting of polyester-polypropylene and butyl rubber are added to the hybrid electric vehicle roof and floor. After improving material, the hybrid electric vehicle interior noise is test. As the result, the car driver’s right ear A-weighting sound pressure levels have been greatly improved. The low-frequency noise below 400 Hz reduced 1.5 dB(A), and the high-frequency noise above 400 Hz reduced 5.2 dB(A). The total noise reduction reached 3.3 dB(A) near the driver’s right ear, which significantly improve the noise, vibration, and harshness performance of hybrid electric vehicle.

Wind-Turbine Trailing-Edge Noise Reduction by Means of Boundary-Layer Suction

Distributed boundary-layer suction has numerically and experimentally shown great potential to reduce flow-induced trailing-edge noise. The paper aims at the transfer of this potential to an industrial full-size wind turbine by means of a dedicated suction system design and, hence, is meant to point out whether the predicted, airfoil-related improvements carry over to wind turbines represented by the N117, not hitherto in liaison with active flow control. Guidance is given through the different design steps involving the suction-followed blowing of the fluid and being continually dictated by industrial constraints and requirements. Because the processes of trailing-edge noise reduction and effective power alteration are intimately bound together, great emphasis is put on an accurate prediction of pump power requirement, with the latter being based on a detailed suction hardware system implying pressure losses across each component. Exploiting the limited installation space, a total trailing-edge noise reduction of 3.6 dB is coupled with a net enhancement of total rotor power of 4.75%. As of a cross-over noise reduction level of 5 dB, the enhancement of aerodynamic power no longer compensates for the pump power requirement and, hence, aeroacoustic demands are implemented to the detriment of aerodynamic performance.

Evaluation of wearing course mix designs on sound absorption improvement of porous asphalt pavement

This paper describes a laboratory procedure to study the sound absorption characteristics of porous asphalt pavement wearing course mix designs, and estimate their contributions to tire-pavement noise reduction. The effects of the following mixture properties were considered: percent porosity of mixture, degree of clogging occurred, and layer thickness. Four porosity levels of porous asphalt were studied: 12%, 16%, 20% and 25%. The mix design with 20% porosity was tested for the effects of clogging and specimen thickness respectively. A dense graded mix was included to serve as a reference for comparison. The effectiveness of the sound absorption and tire-pavement noise reducing capability of the mixtures were evaluated using the laboratory data and field measurements of trial sections. An approximate noise reduction calculation based on laboratory sound absorption measurements is proposed for comparison of different mix designs. The study found that changing the percent porosity from 25% to 12% caused some changes in the frequency characteristics of sound absorption, but made negligible changes in their contributions to tire-pavement noise reduction. On the other hand, clogging of the pores in the mixtures resulted in noticeable decreases in both the sound absorption coefficients and tire-pavement noise reductions. The analysis estimates that about 23–33% of the total tire-pavement noise reduction achieved by the porous asphalt mixtures can be attributed to their sound absorption capability. Finally, changing the thickness of the asphalt mixture tested from 63mm to 200mm had no significant effect on sound absorption and tire-pavement noise reduction.

Use of dual planar jets for the reduction of flow-induced noise

The planar jet has been proposed to reduce the flow-induced noise. However, the self-noise emission from a single planar jet is a limiting factor on the performance based characteristics of this technology. Therefore, this research paper reports an alternative dual planar jets geometry in an attempt to minimize the self-noise of the single planar jet, thus, further enhancing total noise reduction in the application. Tandem cylinders are considered as the generic bluff body, which represents the source of flow-induced noise. Tests are conducted to capture noise reduction effects when using a single planar jet geometry. Subsequently, two different configurations of the dual planar jets geometry were tested in comparison. It is observed that the dual jets geometry achieves more noise reduction when compared to the single jet. Moreover, conclusions are made on the most efficient configuration in the dual jets geometry.

Supply Noise Suppression by Triple-Well Structure

This brief discusses the impact of twin- and triple-well structures on power supply noise, and a substrate model for simulating the power supply noise. We observed <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ss</sub> noise reduction by the resistive network of the p-substrate and <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dd</sub> noise reduction by the junction capacitance of a triple-well structure on a 90-nm test chip. Measurement results also showed that the total noise reduction of a triple-well structure is superior to that of a twin-well structure. The measurement results correlate well with the results obtained from the power supply noise simulation using a hierarchical resistive mesh model. Our simulation-based verification indicates that in common CMOS design, a triple-well structure can reduce the power supply drop by 10%-40% or the decoupling capacitance area by 5%-10%. We also verified that supply drop sensitivity to variation of the well junction capacitance is sufficiently small and that supply noise reduction using a triple-well structure is robust to process variation.

Synthetic mammalian transgene negative autoregulation

Biological networks contain overrepresented small-scale topologies, typically called motifs. A frequently appearing motif is the transcriptional negative-feedback loop, where a gene product represses its own transcription. Here, using synthetic circuits stably integrated in human kidney cells, we study the effect of negative-feedback regulation on cell-wide (extrinsic) and gene-specific (intrinsic) sources of uncertainty. We develop a theoretical approach to extract the two noise components from experiments and show that negative feedback results in significant total noise reduction by reducing extrinsic noise while marginally increasing intrinsic noise. We compare the results to simple negative regulation, where a constitutively transcribed transcription factor represses a reporter protein. We observe that the control architecture also reduces the extrinsic noise but results in substantially higher intrinsic fluctuations. We conclude that negative feedback is the most efficient way to mitigate the effects of extrinsic fluctuations by a sole regulatory wiring.

Active noise control in a forced-air cooling system

This paper discusses the design methodology for the active noise control of sound disturbances in a forced-air cooling system. The active sound cancellation algorithm uses the framework of output-error based optimization of a linearly parametrized filter for feedforward sound compensation to select microphone location and demonstrate the effectiveness of active noise cancellation in a small portable data projector. Successful implementation of the feedforward based active noise controller on a NEC LT170 data projector shows a 20–40 dB reduction per frequency point in the spectrum of external noise of the forced-air cooling system can be obtained over a broad frequency range from 1 to 5 kHz. A total noise reduction (unweighted) of 9.3 dB is achieved.

Aerodynamic Noise Reduction in Pantographs by Shape-smoothing of the Panhead and Its Support and by Use of Porous Material in Surface Coverings

To reduce the aerodynamic noise generated by a pantograph, which is one of the dominant noise sources in high speed trains, the authors have proposed a set of noise reduction techniques, namely, shape-optimization of the panhead, relaxation of aerodynamic interference between the panhead and the articulated frame, and the use of porous material for surface covering. To evaluate the total noise reduction effect of these techniques, they were applied to a prototype pantograph which was tested in a wind tunnel. Test results showed that the prototype pantograph lowered the noise level from the current low-noise pantograph by about 4dB. Furthermore, they also confirmed that the prototype pantograph had sufficient aerodynamic stability against change of attack angle.

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To reduce aerodynamic noise generated by a pantograph, the authors have already proposed some techniques, that is, shape-optimization of a panhead, relaxation of aerodynamic interference between panhead and articulated frame and porous material covering on the surface. To evaluate total noise reduction effect of them, wind tunnel testing was performed with a Shinkansen pantograph to which these techniques were applied. As a result, it was found that noise level of the improved pantograph is lower than that of the currently-used pantograph by about 4dB.