High Frequency Noise Research Articles

Electrical manipulation of a single electron spin in CMOS using a micromagnet and spin-valley coupling

For semiconductor spin qubits, complementary-metal-oxide-semiconductor (CMOS) technology is a promising candidate for reliable and scalable fabrication. Making the direct leap from academic fabrication to qubits fully fabricated by industrial CMOS standards is difficult without intermediate solutions. With a flexible back-end-of-line (BEOL), functionalities such as micromagnets or superconducting circuits can be added in a post-CMOS process to study the physics of these devices or achieve proofs-of-concept. Once the process is established, it can be incorporated in the foundry-compatible process flow. Here, we study a single electron spin qubit in a CMOS device with a micromagnet integrated in the flexible BEOL. We exploit the synthetic spin orbit coupling (SOC) to control the qubit via electric fields and we investigate the spin-valley physics in the presence of SOC where we show an enhancement of the Rabi frequency at the spin-valley hotspot. Finally, we probe the high frequency noise in the system using dynamical decoupling pulse sequences and demonstrate that charge noise dominates the qubit decoherence in this range.

Study on sound absorption characteristic of porous asphalt mixture based on macroscale and mesoscale analysis

To explore the sound absorption characteristics of porous asphalt mixture, the effects of macroscopic parameters of asphalt mixture on sound absorption coefficient (SAC) were studied by the sound absorption coefficient test, and the mesoscopic void structure was investigated by industrial computed tomography (CT) and three-dimensional (3D) reconstruction techniques. The results show that the SAC can be increased by increasing the porosity or thickness and reducing the NMAS. The increase of porosity and the decrease of pavement thickness can better absorb high frequency noise (above 1000 Hz). Through the grey correlation analysis, it can be seen that the SAC of porous asphalt mixture is most affected by the porosity. There is a strong linear relationship between the microscopic void characteristic of porous asphalt mixture and the peak and mean value of SAC.

Non-cooperative underwater acoustic MFSK time-frequency representation optimization method based on sparse reconstruction

The performance of the traditional non-cooperative underwater acoustic (UWA) multiple frequency shift key (MFSK) recognition and parameter estimation method based on time-frequency representation (TFR) is affected by TFR energy divergence. Herein, a sparse TFR estimation model for UWA MFSK is presented. The model exploits the properties of MFSK TFR element sparsity and row sparsity, which can effectively reduce the impact of the channel and does not require any a priori information. To achieve better TFR performance, we propose an inversion fitting method that can effectively improve the frequency resolution, while keeping the time resolution unchanged. Simulation and experimental results show that the Peak Signal to Noise Ratio (PSNR) of the proposed method reaches 21dB with the increase of Signal to Noise Ratio (SNR), indicating that the proposed method has high carrier frequency reconstruction and noise suppression performance. The proposed method can continuously reduce the value of Average Carrier Frequency Offset (ACFO) under inversion fitting method, indicating that inversion fitting method can further reduce the energy divergence and improve frequency resolution.

Impression difference to vehicle interior sound between active and passive driving situation

In near future, autonomous vehicles are expected to be more popular due to the technology development. This transition from active to passive driving condition may change the driver’s impression to vehicle interior sound. And the interior sound improvement for autonomous vehicles should be done according to the difference. In this study, we investigated whether driver’s impression to interior sound changes or not according to the driving situation through subjective evaluation test using a driving simulator. In the test, an original driving simulator was prepared to reproduce identical sounds and conditions at both active and passive driving conditions. As the presented sounds, sound pressure level (SPL) decreased or increased sound at low, mid, or high frequency bands were reproduced with the original sound. Participants drove the simulator under various driving conditions including acceleration and deceleration and evaluated discomfort about the sound. As the result, low or high frequency SPL decreased sounds were evaluated to be more discomfort at passive condition than that at active condition. Especially this tendency became significant at the acceleration and deceleration condition. From these results, high or low frequency noise reduction was found to be important in the future autonomous vehicle development.

Noise levels in a changing Arctic Ocean and its implications for security

Arctic Ocean is undergoing an “Atlantification” of its oceanographic properties. Sea ice retreat and reduction of sea ice age will affect its underwater soundscape, with anthropogenic noise expected to increase due to the exploitation of new maritime routes. The CMRE’s Environmental and Operational Effectiveness Programme conducted a study of the new Arctic oceanographic conditions and ambient noise by deploying in 2021 and in 2022 different moorings equipped with passive acoustic recorders and oceanographic sensors. Data did not show a clear relation between sea-ice concentration and noise levels in the marginal ice zone. However, noise levels indicate that the possible presence of transmissions ducts might increase high frequency noise in the subsurface area. Seasonality and variations in the overall soundscapes were also evident by the presence of sounds from biological sources. In 2023, with the support of the NATO Office of the Chief Scientist, CMRE started a long-term scientific endeavor to study how climate change might affect the Alliance’s security in the maritime domain. A significant research effort is focused on the Arctic, and in June–July 2023 CMRE deployed three deep moorings for monitoring the acoustic-oceanographic conditions in the long term. [Work supported by the NATO Allied Command Transformation.]

FECAM: Frequency enhanced channel attention mechanism for time series forecasting

Time series forecasting (TSF) is a challenging problem in various real-world scenarios, such as industry, energy, weather, traffic, economics, and earthquake warning. TSF demands the model to have a high prediction accuracy. Despite the promising performance of deep learning-based methods in TSF tasks, mainstream forecasting models may sometimes produce results that deviate from the actual ground truth. Our analysis suggests that this may be attributed to the models’ limited ability to capture the frequency information that is abundantly present in real-world datasets. Currently, the Fourier Transform (FT) is the most widely used method for extracting frequency information, but it has some issues that lead to poor model performance, such as high-frequency noise caused by the Gibbs phenomenon and computational overhead of the inverse transformation in the FT-IFT process. To address these issues, we propose a novel frequency enhanced channel attention mechanism (FECAM) that models frequency interdependencies between channels based on Discrete Cosine Transform (DCT), which inherently mitigates the high-frequency noise caused by problematic periodicity during Fourier Transform. This approach improves the model’s capability to extract frequency features and resolves computational overhead concerns that arise from inverse transformations. Our contributions are threefold: (1) We propose a novel frequency enhanced channel attention mechanism that models frequency interdependencies between channels based on DCT, which improves the model’s capability to extract frequency features and resolves computational overhead concerns that arise from inverse transformations; (2) We theoretically prove that our method mitigates the Gibbs phenomenon, which introduces high frequency noise during Fourier Transform. We demonstrate that the result of 1D GAP linearly varies with the lowest frequency component of 1D DCT; (3) We demonstrate the generalization ability of the proposed method FECAM by embedding it into other networks, resulting in significant performance improvements when compared to the original model, with only a minor increase in parameters. Furthermore, we conduct extensive experiments on six different real-world TSF datasets to validate the effectiveness of our proposed model and compare it with several existing state-of-the-art models. Our findings indicate that the FECAM model is superior to these models in terms of accuracy, making it a promising solution for TSF in diverse real-world scenarios. Our codes and data are available at https://github.com/Zero-coder/FECAM.

A quantitative evaluation of the 2nd derivative mode in electron energy loss spectroscopy

The second derivative mode of peak analysis in electron energy loss spectroscopy (EELS) in a Transmission Electron Microscope (TEM) has been quantitatively evaluated in terms of the accuracy of the method. This includes a demonstration of the importance of the second derivative peak width, the second order dependency of the accuracy upon that peak width and effect of high frequency noise in the spectra. It is shown that while the second derivative method is an efficacious and powerful mode of analysis, there are limitations in terms of the number of significant digits in both the spectral values and derived electronic quantities. The case of uranium N4,5 spectral peaks and the 5f population is presented as an example, with UO2 X-ray Absorption Spectroscopy used as a benchmark.

Effect of wavy leading edges on airfoil tonal noise

This work presents numerical studies on the effect of wavy leading edges on airfoil instability tonal noise. Large eddy simulations are conducted for NACA0012 (National Advisory Committee for Aeronautics) airfoils with straight and wavy leading edges. The far-field aerodynamic noise is predicted using the Ffowcs Williams and Hawkings acoustic analogy theory. The inflow Mach number is approximately 0.17 with an angle of attack of 4.3°, and the chord based Reynolds number is 600 000. The present numerical method is first validated by existing numerical results and a semi-empirical model for the straight baseline airfoil. Then, the effects of wavy leading edges on the aerodynamic performance, aeroacoustic performance, and noise reduction mechanisms are discussed in detail. The wavy leading edge is found to be detrimental to the mean aerodynamic performance with a decreased lift and increased drag. However, the lift fluctuations are significantly reduced. The instability tonal noise and its harmonic are totally removed by the wavy leading edges, while an extra broadband hump appears at the middle frequency. The low frequency and high frequency noise are also increased by the wavy airfoil. The laminar separation bubble is removed, and the flow separation is decreased by the wavy airfoil in the vicinity of the trailing edge. The pressure fluctuations around the trailing-edge are considerably diminished, and the spanwise coherence spectra are also significantly reduced by the wavy airfoil. Furthermore, it is noteworthy that the coherence reduction spectrum at the source is almost consistent with the far-field noise reduction spectrum.

High stability and low noise laser-diode end-pumped Nd: YAG ceramic passively Q-switched laser at 1123 nm based on a Ti3C2T x -PVA saturable absorber

We report a high repetition frequency, high power stability and low laser noise laser-diode (LD) end-pumped Nd: YAG ceramic passively Q-switched laser at 1123 nm based on a Ti3C2T x -polyvinyl alcohol (PVA) film as a saturable absorber (SA). A Brewster polarizer (BP) and a birefringent crystal (BC) are incorporated to enable frequency selection and filtering for the passively Q-switched 1123 nm pulsed laser to improve the power stability and reduce the noise. When the pump power is 5.1 W, an average output power of 457.9 mW is obtained, corresponding to a repetition frequency of 1.09 MHz, a pulse width of 56 ns, a spectral line width of 0.65 nm, a power instability of ±0.92%, and a laser noise of 0.89%. The successful implementation of the “Ti3C2T x -PVA film passively Q-switching” combined with “frequency selection and filtering of BP + BC” technology path provides a valuable reference for developing pulsed laser with high repetition frequency, high stability and low noise.

Stress recovery at home: Effects of the indoor visual and auditory stimuli in buildings

In order to explore the potential contribution of the visual and auditory environment on the mental stress recovery of people in indoor environment, the visual, auditory, and visual-auditory stimuli were selected to design 3 kinds of restorative environments, under which the subjects experienced the baseline stage, the stress-induction stage, and the recovery stage, in sequence. The stress was induced with the continuous high frequency noise at 70–80 dB. The Electrocardiogram (ECG) data of the subjects were recorded during the whole experiment, and the heart rate variability (HRV) analysis was conducted, producing the mean heart rate (HR), the root mean square successive difference (RMSSD), as well as the ratio of low to high frequency power (LF/HF). The stress level was evaluated with these indexes during the whole experiment. Results showed that mean HR and LF/HF were higher than that of the baseline after the stress-induction, while the mean RMSSD was significantly lower than the baseline level, which implied the stress rise was resulted from the stress-induction stage. In addition, it was found that the mean HR and LF/HF reduced after the participants experienced the visual, the auditory and the visual-auditory restorative environments, but the mean RMSSD increased, which suggested the attenuated stress level. Furthermore, it was observed that the RMSSD was the most sensitive to the stress. Based on that, the time for the stress-recovery was estimated with the mean RMSSD. Results showed that the visual and visual-auditory stimuli produced better acute recovery effect than that of the auditory, but in the long run the auditory stimulus could bring the most stress reduction, followed by the visual stimulus. This study produced a potential solution for the stress recovery at home, which could be important for the improvement of the mental health, cognitive performance and the productivity of the occupants.

Analysis of flow field and aerodynamic noise of marine gas turbine air intake system.

The aerodynamic noise of air intake system is one of the main noise sources of a gas turbine power plant. In this study, large eddy simulation in conjunction with acoustic finite element method were used to simulate the flow field and acoustic field of the air intake system of marine gas turbine. Based on the acoustic analogy methods, the internal sound source distributions and inlet radiated noise characteristics of the air intake system under different working conditions and wind speeds were analyzed. The simulated flow fields show that the highest vorticity magnitude occurs around the output shaft as the flow largely separates when passing through. The total pressure loss across the intake system increases with the increasing of the air mass flow rate and the ambient wind speed. The acoustical results show that the low frequency noise of the intake system is more prominent than the high frequency noise. The far field sound pressure level increases quadratically with the intake mass flow rates. The introduction of the ambient wind speed at the inlet boundaries reduces the high frequency aerodynamic noise of the intake system, but the overall sound pressure level of the aerodynamic noise increases with the wind speeds.

Underwater Acoustic Noise Cancellation Scheme Combining Kalman Filter With Adaptive FxNLMS

Underwater environments are more challenging than that of terrestrial. The performance of a controller or the augmented system as a whole depends on the real measured data, so noise on data readings can be fatal. To effectively and adaptively control lower and higher frequency noise, the Active Noise Cancellation (ANC) was developed. Designing a system and the parameter of modified FxLMS for reducing noise, and disturbance of sensor data is the primary focus of this paper. The required equation will be analyzed and discussed briefly. Moreover, the system will be simulated in MATLAB and then the filtered result will be analyzed. Based on the simulation results, the proposed model can filter out signals with noise, particularly when there is a significant variation in the data and no knowledge of the noise frequency that might affect sensor readings.

The Effects and Mechanisms of Periodic-Carrier-Frequency PWM on Vibrations of Multiphase Permanent Magnet Synchronous Motors

High-frequency vibration and noise induced by pulse width modulation (PWM) deteriorate the acoustic performance of permanent magnet synchronous motor (PMSM) drives. Periodic-carrier-frequency PWM (PCFPWM) is an effective method that can disperse the high-frequency harmonics to a wider frequency band, thereby suppressing the peak harmonic. This paper presents a detailed study on how exactly PCFPWM affects both the low-frequency and high-frequency vibrations of PMSMs. It is revealed that PCFPWM actually deteriorates low-frequency vibrations of the motor, due to unwanted side effect of additional AC components in d- and q-axis currents and thus increased torque pulsations. But this can be remedied by quasi-proportional resonant control of corresponding current harmonics. For high-frequency vibrations, the paper thoroughly studies the effects of PCFPWM on current harmonics and the zero-order electromagnetic (EM) force acting on motor stator teeth. Compared with the experimental vibration results, it is found that high-frequency zero-order EM force is the direct and major cause of EM vibrations induced by PCFPWM. This paper provides the theoretical basis for future optimization of PCFPWM based on the zero-order EM force as a direct vibration metric.

High-frequency Noise Removal of Vintage Songs in Audio Cassettes using Signal Processing Techniques


 From 1960 to the early 2000s, the audio cassette was one of the three most used storage devices for prerecorded music, alongside gramophone records (LPs) and compact discs (CDs). A compact cassette consists of two miniature spools, between which a magnetic tape is passed and wound. The tape head in tape recorders and cassette players is used to store and play audio tracks in these magnetic tapes by converting the electric signal to a magnetic fluctuation and vice versa. The sound quality of an audio track recorded on a compact cassette is decent. However, as these cassettes are stored in the Earth’s magnetic field for longer periods, the effect from it influences magnetic particles to change their orientation and distort the recorded audio signal. As a result, high-frequency noise is generated in the audio signal, resulting in a great disturbance when listening to songs and other audio recordings on vintage cassettes.
 168Therefore, the removal of such noises while minimizing the impact on the original audio signal will make sure the listener gets to enjoy the original quality of the vintage audio recordings. Fourier transform of a given distorted audio file (in “wav” format) was obtained to identify the high-frequency noise using Wolfram Mathematica 12.3. Then a variable “m” was introduced to the program to identify magnitudes of high-frequency components and remove their effect on the original audio recording. A trial-and-error approach was taken to identify the adequate “m" value for each channel of a given audio signal. Vintage songs were used to evaluate the accuracy of the developed method in this study. It was identified that the suitable “m” value changes for each channel in each song. Therefore, it is impossible to state a constant value for the variable “m”. However, the accuracy of the output also depends on the hearing frequency of the person, and the audio equipment being used. As an application, this technique can be used to conserve vintage songs that were originally stored in compact cassettes and spools, because it allows the user to control the number of high-frequency components removed from the distorted audio signal.
 Keywords: Signal Processing Techniques, Fourier Transforms, Mathematica, Noise Removing,Audio Cassettes

An inverse Q filtering method with adjustable amplitude compensation operator

The generalized stable inverse Q filtering method can flexibly select the intensity and frequency bandwidth of amplitude compensation operator according to the signal-to-noise ratio (SNR) of seismic data. When processing noisy seismic data, the method can avoid enhancing some noise energy by adjusting parameters. However, this method still faces the problem of noise amplification when the SNR of seismic data is low. In order to solve this problem, this paper proposes an adjustable amplitude compensation operator, which can suppress part of the high frequency noise energy effectively without affecting the intensity of the amplitude compensation by introducing a dynamically adjustable amplitude compensation curve. Combining this operator with the generalized stable inverse Q filtering algorithm, an inverse Q filtering method with adjustable amplitude compensation operator is developed. Compared with the generalized stable inverse Q filtering method, this method has the ability of adjustable amplitude compensation and adjustable noise suppression. When inverse Q filtering is performed on the seismic records, the compensation strategy can be more flexible according to its quality and processing requirements. In addition, this method almost not introduce extra calculation cost, and has the characteristics of simplicity and high efficiency. Theoretical and practical seismic records show that the proposed method can further improve the SNR and resolution of seismic records after inverse Q filtering.

A quartz crystal microbalance (QCM)-based easy setup device for real-time mass change detection under high-power RF plasma.

Sensing technologies serve a crucial role in monitoring and testing surface properties in biosensors, thin films, and many other industries. Plasma treatments are routinely used in most of these technologies to modify the surfaces of materials. However, due to the high radio frequency (RF) noise in plasma processes, real-time surface tracking is still rather difficult. In this study, we aim to construct an easy-to-set up mass change detection system capable of operating under RF plasma conditions. For this purpose, we have presented a novel technique that utilizes the quartz crystal microbalance sensor to detect mass changes in different plasma environments. The constructed device was then tested under 13.56MHz, 100W plasma atmosphere. The results showed that the resonance frequency of a crystal was successfully measured with 1.0Hz resolution under the impact of plasma-induced high power of RF noise. Moreover, as a preliminary study, we used ethylenediamine (EDA) to track changes in resonance frequency under plasma conditions and observed noise-free signals in frequency-voltage curves. Furthermore, the system's sensitivity was found to be 3.8 ng/Hz, with a test molecule (EDA) deposition of about 380 ng in the RF plasma atmosphere. Overall, this study focused on creating a relatively new approach for detecting the real-time mass change in a strong RF environment, which we believe could be an improved and easy-to-set up technique for plasma-based processes such as surface coating, etching, and activation.

Conducted Noise Prediction for DC–DC Converter by Noise Source Model Accounting for Switching Fluctuation

The switching fluctuation of a dc–dc converter causes jitter and makes the conducted noise time-variant. Averaging-mode measurement with an oscilloscope or other instruments partially removes higher-frequency noise. Therefore, switching fluctuation affects the accuracy of noise prediction in using a black-box noise source model with measurement-based parameter identification. To address this issue, we proposed an approach to address the switching fluctuation effect on conducted emissions from the dc–dc converter. First, we investigate the effect of switching fluctuation by studying the difference between noise signals with and without fluctuation and estimating the reduction due to fluctuation. Then, to facilitate model parameter identification, we focus on the peak detected noise signal and improve the prediction accuracy of the peak detected noise by decomposing the measured noise signal into ripple noise and turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> and turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> spike noises. As a result, the peak detected noise spectrum after removing switching fluctuation can be predicted within a 3-dB error up to 200 MHz. Our experimental results show that the noise spectrum predicted by accounting for the reduction due to switching fluctuation agrees well with the spectrum obtained by averaging-mode measurement.

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.