High Frequency Noise Research Articles

Visibility of Vegetation High-Impedance Fault Low-Frequency and High-Frequency Signatures

This letter exhibits the presence of High-Frequency (HF) current signatures of arcing in Vegetation High Impedance Fault (VeHIF) events. Zero-crossing arcing discontinuities are shown to have varying widths causing different levels of HF noise bursts depending on how aggressively the 50-Hz waveform gets distorted. The work has identified that the temporal growth in HF disturbances often occurs quicker than those linked to the third harmonic or the entire Low-Frequency (LF) spectrum. In 59.2 % of a dataset of 125 phase-to-earth (ph-to-e) faults, the growth in HF spectrum was identified to occur faster than the third-harmonic or the entire LF spectrum. The HF spectrum had an average lead time of 26.58 s over the LF spectrum. The LF indicator performed better in only 15 tests (12 %) with an average lead time of 9.6 s. In 13 tests (10.4 %), all three indicators concurrently reached the set normalized threshold.

Sound attenuation by acoustic metamaterials applied to kitchen hoods

In a society where the vast majority of people spend their time inside buildings or vehicles, the need to filter the air is essential to ensure a certain level of comfort. The integration of air exchanger systems in these enclosed spaces generates noise pollution which can deteriorate the quality of the air. Thus, controlling the noise generated by these systems becomes a major challenge for the construction industry. Recent traditional solutions such as acoustic sonic crystals only allow high frequency noise control. One solution is the incorporation of inner structured acoustic materials for the control of low frequency transmission. This paper proposes a coupling of sonic crystals and structural acoustic materials for the control of sound transmission at low and high frequencies. To achieve this, research and simulations of the acoustic properties of various metamaterial models under the COMSOL software were established as well as a system of the selected solutions, using the transfer matrix method. Experimental impedance tube analyses are being carried out for varying geometries, along with a fabrication method for prototyping.

Time–frequency multiresolution of fault-generated transient signals in transmission lines using a morphological filter

The ongoing transformation of electrical power systems highlights the weaknesses of the protection schemes of traditional devices because they are designed and configured according to traditional characteristics of the system. Therefore, this work proposes a new methodology to study the fault-generated high frequency transient signals in transmission lines through multiresolution analysis. The high frequency components are determined by a new digital filtering technique based on mathematical morphology theory and a spectral energy index. Consequently, wide spectra of signals in the time–frequency domain are obtained. The performance of this method is verified on an electrical power system modeled in ATP-Draw, where simulation and test signals are developed for different locations, fault resistances, inception angles, high frequency noises, sampling frequencies, types of faults, and shapes of the structuring element. The results show the characteristics of the fault such as the traveling wave frequency, location, and starting time.

Applying vertical greening systems to reduce traffic noise in outdoor environments: Overview of key design parameters and research methods

Vertical greening can be used to absorb and scatter sound, which may reduce noise levels in street canyons. In this paper, a literature review is presented, which combines results and methods from over 40 individual studies. The article describes the guiding principles behind the acoustic effects of vertical greening and provides an overview of the prevalent research methods. The article shows that vertical greenery is effective for the reduction of mid and high frequency noise, unless air cavities or resonators are introduced inside, or behind, the systems. The review also reflects on studies with an emphasis on the application of vertical greenery in streets and urban blocks. The aim of the article is to set out the key design parameters for noise reduction that can be achieved by vertical greening, focusing on designers and engineers.

High-Fidelity Reproduction of Visual Signals by Electrical Stimulation in the Central Primate Retina.

Electrical stimulation of retinal ganglion cells (RGCs) with electronic implants provides rudimentary artificial vision to people blinded by retinal degeneration. However, current devices stimulate indiscriminately and therefore cannot reproduce the intricate neural code of the retina. Recent work has demonstrated more precise activation of RGCs using focal electrical stimulation with multielectrode arrays in the peripheral macaque retina, but it is unclear how effective this can be in the central retina, which is required for high-resolution vision. This work probes the neural code and effectiveness of focal epiretinal stimulation in the central macaque retina, using large-scale electrical recording and stimulation ex vivo The functional organization, light response properties, and electrical properties of the major RGC types in the central retina were mostly similar to the peripheral retina, with some notable differences in density, kinetics, linearity, spiking statistics, and correlations. The major RGC types could be distinguished by their intrinsic electrical properties. Electrical stimulation targeting parasol cells revealed similar activation thresholds and reduced axon bundle activation in the central retina, but lower stimulation selectivity. Quantitative evaluation of the potential for image reconstruction from electrically evoked parasol cell signals revealed higher overall expected image quality in the central retina. An exploration of inadvertent midget cell activation suggested that it could contribute high spatial frequency noise to the visual signal carried by parasol cells. These results support the possibility of reproducing high-acuity visual signals in the central retina with an epiretinal implant.SIGNIFICANCE STATEMENT Artificial restoration of vision with retinal implants is a major treatment for blindness. However, present-day implants do not provide high-resolution visual perception, in part because they do not reproduce the natural neural code of the retina. Here, we demonstrate the level of visual signal reproduction that is possible with a future implant by examining how accurately responses to electrical stimulation of parasol retinal ganglion cells can convey visual signals. Although the precision of electrical stimulation in the central retina was diminished relative to the peripheral retina, the quality of expected visual signal reconstruction in parasol cells was greater. These findings suggest that visual signals could be restored with high fidelity in the central retina using a future retinal implant.

Hybrid-integrated wideband tunable optoelectronic oscillator.

As a photonic-based microwave signal generation method, the optoelectronic oscillator (OEO) has the potential of meeting the increasing demand of practical applications for high frequency, broadband tunability and ultra-low phase noise. However, conventional OEO systems implemented with discrete optoelectronic devices have a bulky size and low reliability, which extremely limits their practical applications. In this paper, a hybrid-integrated wideband tunable OEO with low phase noise is proposed and experimentally demonstrated. The proposed hybrid integrated OEO achieves a high integration level by first integrating a laser chip with a silicon photonic chip, and then connecting the silicon photonic chip with electronic chips through wire-bonding to microstrip lines. A compact fiber ring and an yttrium iron garnet filter are also adopted for high-Q factor and frequency tuning, respectively. The integrated OEO exhibits a low phase noise of -128.04 dBc/Hz @ 10 kHz for an oscillation frequency of 10 GHz. A wideband tuning range from 3 GHz to 18 GHz is also obtained, covering the entire C, X, and Ku bands. Our work demonstrates an effective way to achieve compact high-performance OEO based on hybrid integration, and has great potential in a wide range of applications such as modern radar, wireless communication, and electronic warfare systems.

PO-04-075 TRANSVENOUS CARDIAC DEFIBRILLATOR WITHOUT INTERACTION WITH THE MAGNETIC TITANIUM BEADS SYSTEM FOR GASTROESOPHAGEAL REFLUX DISEASE

Gastroesophageal reflux is increasingly treated with LINX®, a flexible bracelet of magnetic titanium beads (not MRI compatible) that is laparoscopically implanted to wrap around the gastroesophageal junction for providing tone/support aiding passive relaxation of a weak lower esophageal sphincter with peristalsis. The FDA currently cautions against concurrent use of the LINX® system with cardiac implantable electronic devices (CIEDs) given that the risk of electromagnetic interference (EMI) is unknown, and safety has not been established. We assessed the safety of a transvenous ICD in a patient with the LINX® system. Case Report 59 year old male who previously had the LINX® system implanted after hiatal hernia repair for refractory reflux. Shortly after, he was then diagnosed with apical hypertrophic cardiomyopathy with obstruction (NYHA Class I, genetic testing revealed VUS in CSRP3). Given non-sustained VT on cardiac event monitoring, family history of sudden cardiac death (SCD) and late gadolinium enhancement on cardiac magnetic resonance imaging with a calculated 5-year SCD risk 4.1%, he was recommended ICD implantation for primary prevention. Patient underwent an uneventful transvenous dual chamber defibrillator implantation. Although we do not routinely perform (DFT) testing at our institution, given the coexisting LINX® system in close proximity to the RV lead, we elected to proceed with DFT Testing, which was successful (1 induction: T-wave shock from sinus to VF, 30J delivered successfully to sinus with 7s charge time, no ATP, 70 ohms impedance). Patient underwent routine remote device interrogations and at 1-year follow up (which included an in-person device interrogation), continues to have normal lead parameters (sensing, impedance, threshold), minimal atrial or ventricular pacing, and no recurrent arrhythmias including NSVT (was started on verapamil). Specifically, patient received no inappropriate shocks, and no high frequency noise episodes were detected. We present the first case report of a patient who had a concomitant dual chamber ICD that was implanted shortly after a LINX device placement. We demonstrate normal DFTs at implant and no device interaction at 1 year follow-up, suggesting that ICD implantation without removal of the LINX device might be reasonable. Decision-making for cardiac device implantation decisions in such patients should consider additional theoretical risks until additional data with more patients is available.

Personal noise exposure during daily commutes and subjectively reported stress: A trip stage level analysis of MobiliSense data

BackgroundThe auditory and non-auditory health effects of noise have long been established in the literature but previous studies have mainly been in the context of occupational risk. Recent research suggests that daily noise exposures occurring during social activities and commute may be associated with higher psychological stress. Our aim was to explore the association between modes of transportation and noise on the one hand and noise exposures and reported stress on the other hand. Although existing literature shows that noise exposure is especially high during commutes, studies on the topic have been sparse due to cost and logistic constraints; furthermore, sample sizes have been small. MethodsThe present study uses data collected on the daily commutes of 253 participants of the Mobilisense cohort study between 2018 and 2020. Personal dosimeters were used to measure noise exposure by frequency bands over a period of 4 days, resulting in a sample of 7800 trip stage windows. Participants reported trip stress levels during an a posteriori phone mobility survey on a scale from 1 (no stress) to 7 (significantly stressful conditions). Modes of transportation (metro, car, walking, etc.) were collected from the same mobility survey based on Global Positioning System (GPS) receivers. ResultsWhile all transport modes resulted in higher exposure to low frequency noise compared to walking, all modes but tramway and driving or being the passenger of a car were associated with an increased exposure to high frequency noise. The LAeq noise indicator (overall noise) was associated with reported stress: for every 10 dB(A) increase in LAeq, individuals reported experiencing 1.118 times (95% confidence interval: 1.067, 1.172) higher levels of stress. Multiple noise indicator models did not show evidence that specific frequency components were associated with stress beyond overall noise. ConclusionOur findings suggest that noise exposure during commutes vary according to modes of transportation. Given that noise exposure resulted in higher reported levels of stress, future research should examine transportation noise effects on physiological variables.

Vibration control of commercial vehicle drive axles based on modification of helical gears

High-frequency noise, which is called gear whine, is a common noise, vibration, and harshness (NVH) problem in the drive axles of commercial vehicles. Although this problem can be solved by gear modification, it is difficult to suppress gear whine effectively because of the difficulty in the selection of the modification parameters. In this paper, on the basis of the combination of the design of experiment (DOE) method and the artificial fish swarm algorithm (AFSA), a method for arriving at the optimal modification design to reduce the peak-to-peak transmission error (PPTE) of helical gear pair is proposed. The method is verified to be effective for reducing gear PPTEs and drive axle vibrations by vehicle road tests with optimized sample pieces. In addition, it is more efficient than the existing methods, as indicated by the results of the gear contact analysis of a coupled dynamic-finite element (FE) model and NVH performance in the tests.

Study on Denoising Method of Vibration Signal Induced by Tunnel Portal Blasting Based on WOA-VMD Algorithm

Because of the impact of the complex environment of tunnel portals, the measured blasting vibration signals in a tunnel portal contains a lot of high-frequency noise. To achieve effective noise reduction, a novel method of noise reduction for blasting vibration signals based on the whale optimization algorithm (WOA) optimized with the variational mode decomposition (VMD) algorithm was proposed. The WOA algorithm is used to optimize globally for the mode number K and penalty factor α of VMD for measured signals and to determine the optimal parameters of [K, α], and to obtain the intrinsic mode function (IMF). Multi-scale permutation entropy (MPE) was used to identify and remove noise components in IMF, and then the reserved IMF was reconstructed to achieve a denoised signal. The method is applied to the blasting vibration analysis of the Xiali tunnel of the Jixin expressway in the Henan Province. Results indicate that the novel method can acquire the optimal decomposition mode number and identify the high frequency noise. Its denoising effect is better than the conventional VMD algorithm and the complete ensemble empirical mode decomposition with adaptive ability (CEEMDAN), which verifies the self-adaptivity and effectiveness of the WOA-VMD denoising method.

Dental drill noise reduction using a commercially-available earplug device.

The dental handpiece noise in a dental surgery is concerning to both patients and staff as a major cause of dental phobia in patients and potential hearing loss in clinical staff. High-frequency noise generated by dental handpieces is considered to be the worst of the many noises in a dental clinic. Methods to reduce this noise have been proposed and either passive or active noise reduction headphones are often suggested. However, in a dental surgery environment, the need for good verbal communication with the patient needs to be maintained. As a result, this paper aims to evaluate one proprietary anti-noise device considered suitable for this specific purpose. Lab-based experiments were set up and carried out to evaluate QuietOn, using GRAS 43AG-1 Ear and Cheek Simulator to mimic a section of the human head and ear to represent the acoustic characteristics of an actual ear. Two types of dental drill noise recordings, one for electric motor-driven and another one for air turbine-driven, were played back through high-definition speakers. Sound data captured by the simulator are then visualised and plotted using MATLAB for analysis. QuietOn is effective at low frequencies (< 1kHz). However, when dealing with high-frequency noise such as dental handpieces it is ineffective yet subdues verbal communication. Further development of passive or active noise cancellation earplugs is still needed to target dental handpiece noise while maintaining verbal communication.

Spectrum Shape Based Roller Bearing Fault Detection and Identification

This article describes a combination of numerical methods of automated fault detection and identification in rolling bearings, even when there is a limited knowledge about inspected bearings and their characteristic frequencies in particular. The most important feature is global approach to solving the stated problem using several rolling bearing diagnostic methods and techniques which work simultaneously and complement each other. These include the well-known Hilbert-based envelope, Discrete Wavelet Transform and Fourier Transform as well as new Outer Envelope Filtering, Pulse Train Scanning, spectrum shape analysis and novel application of known signal processing tools like Fuzzy Logic and Continuous Wavelet Transform. Combination of partial results obtained by each path allows for judging the probabilities of different fault types (outer-race, inner-race and roller). Two techniques additionally used here are spectrum scanning by a train of harmonic pulses (Pulse Train Scanning) and an outer envelope filter which removes high frequency noise, but enhances the most important short time diagnostic symptoms, which are often removed by standard filtering. A combination of such solutions allows for unambiguous and precise localization of characteristic fault frequencies in a spectrum without initial knowledge about their expected values.

Research on ICG Signal Preprocessing and Feature Recognition Method Based on CEEMDAN

A method based on Complete Ensemble Empirical Mode Decomposition with Adaptive Noise (CEEMDAN) combined with differential, threshold iterative processing and signal segmentation is proposed to preprocess the impedance cardiogram (ICG) signal and identify multiple feature points. First, CEEMDAN decomposes the ICG signal to obtain multiple modal function components (IMF). According to the highfrequency and low-frequency noise frequencies existing in the ICG, the correlation coefficient method is used to remove the interference noise, and then the ICG signal after noise removal is differentiated and segmented. Looking for feature points B, C, X, and perform the above processing on the signals of 20 volunteers collected clinically to evaluate the accuracy of the algorithm. The final results show that the method can locate the feature points with an accuracy rate of 95.8%, the feature positioning effect is good.

Multiple ECG segments denoising autoencoder model.

Denoising autoencoder (DAE) with a single hidden layer of neurons can recode a signal, i.e., converting the original signal into a noise-reduced signal. The DAE approach has shown a good performance in denoising bio-signals, like electrocardiograms (ECG). In this paper, we study the effect of correlated, uncorrelated and jittered datasets on the performance of the DAE model. Vectors of multiple concatenated ECG segments of simultaneously recorded Einthoven recordings I, II, III are considered to establish the following dataset cases: (1) correlated, (2) uncorrelated, and (3) jittered. We consider our previous work in finding the optimal number of hidden neurons receiving the input signal with respect to signal quality and computational burden by applying Akaike's information criterion. To evaluate DAE, these datasets are corrupted with six types of noise, namely mix noise (MX), motion artifact noise (MA), electrode movement (EM), baseline wander (BW), Gaussian white noise (GWN) and high-frequency noise (HFN), to simulate real case scenario. Spectral analysis is used to study the effects of noise whose power spectrum may overlap with the power spectrum of the wanted signal on DAE performance. The simulation results show (a) that the number of hidden neurons to denoise multiple correlated ECG is much lower than for jittered signals, (b) QRS-complex based ECG alignment preferable, (c) noises with slightly overlapping power spectrum, like BW and HFN, can be easily removed with sufficient number of neurons, while the noise with completely overlapping spectrum, like GWN, requires a very low-dimensional and thus coarser reduction to recover the signal. The performance of DAE model in terms of signal-to-noise ratio improvement and the required number of hidden neurons can be improved by utilizing the correlation among simultaneous Einthoven I, II, III records.

Influence of contact parameters on the radiated noise from an automotive drum brake

Drum brakes are the major source of noise and vibrations in the automobile as the drum acts as a significant source of the noise. High-frequency noises are generated at the interfacial contact between the brake shoe and brake drum. Hence, the variation in the contact parameters (friction, contact stiffness, and contact damping) will significantly affect the vibro-acoustic noise emanating from the drum brake. The current work quantifies the variation in vibro-acoustic noise due to an asymmetry in the contact of leading and trailing shoes with the drum. The overall sound pressure level is estimated numerically using a finite element model of the drum brake. Multiple spring-like components in parallel between the brake shoe and the drum imitate the contact in real drum brakes. The numerical model predicts the noise generated by a symmetric system (without any asymmetry defects) and a system with controlled asymmetric defects introduced into the model. The results show that the overall sound pressure level is a strong function of the contact parameters. The current research is envisioned to better the selection of contact parameters and hence the drum and shoe properties.

Analysis of high frequency noise sources on air conditioning variable speed compressors

The improvement on energy consumption requires application of new technologies in existing products. On the past decades, optimization of power consumption on variable speed rotary compressors for air conditioning applications was achieved by replacing induction motors to brushless DC (BLDC) motors driven by a frequency inversor. Besides the positive behavior of the motor type change on compressor efficiency, acoustic problems on the compressor became more complex. This article makes a revision of the main noise generation mechanism by BLDC motors of an air conditioning compressor via numerical finite element and experimental analysis aiming a noise reduction on a tonal component around 8 kHz band. Results indicate harmonic components on the forces exciting some specific resonance frequencies of the stator. The harmonic components show up in the force signals via pulse width modulation of the inverter electronic controller. The structure-born noise is radiated through the compressor shell. Among the possibilities to mitigate the noise issues, it was chosen to optimize the electronic control reduced the excitation levels of the stator and the tonal component of 8 kHz band in about 10 dB improving the sound quality of the compressor.

A Study on the Noise Optimization through the Analysis of Electric Vehicle Noise Paths

Since an internal combustion engine is not required for electric vehicle, the electric vehicle's noise is much lower than that of conventional internal combustion engine based vehicle. However, a road noise and wind noise that used to be masked by engine noise became the critical noise factors. Moreover, the electric vehicle generates a specific current conversion noise and motor high frequency noise that provides an unpleasant sound environment for drivers and passengers. In this study, therefore, the noise path of the electric vehicle was identified through Power Based Noise Reduction (PBNR) and Acoustic Transfer Function (ATF) tests. As a result of analyzing the noise path, it was confirmed that the rear side of vehicle was weak in terms of noise. As a countermeasure against this, it was confirmed that interior noise level could be improved by reinforcing the luggage side.

Flat Fresnel-spiral acoustic metamaterials composed of several arms ventilated metamaterials for simultaneous broadband sound absorption and air circulation

With a steep rise in the urban population requiring an increased number of buildings, public and private transport systems, urban noise is posing a serious environmental problem affecting health. To attenuate the effect on the well-being of human health, a variety of conventional sound-absorbing materials suitable at mid and higher-frequency noise absorption are commonly being used but low and mid-frequency noise remains a challenge. These applications are further limited by the acoustic performance and ventilation efficiency in conventional noise barrier limits of their fields. Acoustic metamaterial presents a unique solution as an artificially designed material showing low-frequency noise mitigation. A novel subwavelength device having thickness of 15mm (&lt;2 cm) ,with potential application in noise mitigation and air ventilation solution is presented herein. In this study, the design and fabrication of a small prototype based on a Fresnel-spiral shape composed of several arms are performed. Numerical and experimental investigations were carried out to determine the acoustical properties of the proposed ventilated metamaterial in terms of sound absorption and sound transmission loss. The experimental investigation shows significant sound absorption with a high bandwidth (more than one octave in the range of &gt; 900 Hz ), acoustic properties leading to potential applications in urban noise control for low and mid-frequency ranges.

A Fitted empirical demodulation for low frequency electrical signal evaluation

Empirical Demodulation (ED) is a technique used to build a discrete signal, called an empirical envelope, from a modulated time sequence. For example, in three-phase induction motors, this envelope can carry fault frequency data that allows the machine health status to be evaluated during a spectral analysis. However, due to mathematical reasons, the method is very sensitive to the amplitude oscillations within the signal. When these oscillations are unwanted, as in the presence of measurement noise, the results can be strongly affected. This work proposes an iterative and adjustable version of the ED that considerably reduces its sensitivity to the presence of high frequency noise, thus eliminating the need for signal pre-filtering. To prove the effectiveness of the Fitted Empirical Demodulation, the authors applied the new tool in motor current signals for analysis of the rotor bars conditions.

TRPV4-induced Neurofilament Injury Contributes to Memory Impairment after High Intensity and Low Frequency Noise Exposures

ObjectiveExposure to high intensity, low frequency noise (HI-LFN) causes vibroacoustic disease (VAD), with memory deficit as a primary non-auditory symptomatic effect of VAD. However, the underlying mechanism of the memory deficit is unknown. This study aimed to characterize potential mechanisms involving morphological changes of neurons and nerve fibers in the hippocampus, after exposure to HI-LFN. MethodsAdult wild-type and transient receptor potential vanilloid subtype 4 knockout (TRPV4-/-) mice were used for construction of the HI-LFN injury model. The new object recognition task and the Morris water maze test were used to measure the memory of these animals. Hemoxylin and eosin and immunofluorescence staining were used to examine morphological changes of the hippocampus after exposure to HI-LFN. ResultsThe expression of TRPV4 was significantly upregulated in the hippocampus after HI-LFN exposure. Furthermore, memory deficits correlated with lower densities of neurons and neurofilament-positive nerve fibers in the cornu ammonis 1 (CA1) and dentate gyrus (DG) hippocampal areas in wild-type mice. However, TRPV4-/- mice showed better performance in memory tests and more integrated neurofilament-positive nerve fibers in the CA1 and DG areas after HI-LFN exposure. ConclusionTRPV4 up-regulation induced neurofilament positive nerve fiber injury in the hippocampus, which was a possible mechanism for memory impairment and cognitive decline resulting from HI-LFN exposure. Together, these results identified a promising therapeutic target for treating cognitive dysfunction in VAD patients.