Transient Noise Research Articles

Characterization of transient noise in Advanced LIGO relevant to gravitational wave signal GW150914

On 14 September 2015, a gravitational wave signal from a coalescing black hole binary system was observed by the Advanced LIGO detectors. This paper describes the transient noise backgrounds used to determine the significance of the event (designated GW150914) and presents the results of investigations into potential correlated or uncorrelated sources of transient noise in the detectors around the time of the event. The detectors were operating nominally at the time of GW150914. We have ruled out environmental influences and non-Gaussian instrument noise at either LIGO detector as the cause of the observed gravitational wave signal.

When, where and how to estimate persistent and transient efficiency in stochastic frontier panel data models

In this paper we examine robustness of a recently developed panel data stochastic frontier model that allows for both persistent and transient (also known as long-run and short-run or time-invariant and time-varying) inefficiency along with random firm-effects (heterogeneity) and noise. We address some concerns that the practitioners might have about this model. First, given that there are two random time-invariant components (persistent inefficiency and firm-effects) the concern is whether the model can accurately identify them, and if so how precisely can the model estimate them? Second, there are two time-varying random components (transient inefficiency and noise), and the concern is whether the model can separate noise from transient inefficiency, and if so how precisely can the model estimate transient inefficiency? Third, how well are persistent and transient inefficiency estimated under different scenarios, viz., under different configurations of the variance parameters of the four random components? Given that the model is quite complex, relatively new and becoming quite popular in the panel efficiency literature, we feel that there is need for a detailed simulation study to examine when, where and how one can use this model with confidence to estimate persistent and transient inefficiency.

Interplanetary space weather effects on Lunar Reconnaissance Orbiter avalanche photodiode performance

Space weather is a major concern for radiation-sensitive space systems, particularly for interplanetary missions, which operate outside of the protection of Earth's magnetic field. We examine and quantify the effects of space weather on silicon avalanche photodiodes (SiAPDs), which are used for interplanetary laser altimeters and communications systems and can be sensitive to even low levels of radiation (less than 50 cGy). While ground-based radiation testing has been performed on avalanche photodiode (APDs) for space missions, in-space measurements of SiAPD response to interplanetary space weather have not been previously reported. We compare noise data from the Lunar Reconnaissance Orbiter (LRO) Lunar Orbiter Laser Altimeter (LOLA) SiAPDs with radiation measurements from the onboard Cosmic Ray Telescope for the Effects of Radiation (CRaTER) instrument. We did not find any evidence to support radiation as the cause of changes in detector threshold voltage during radiation storms, both for transient detector noise and long-term average detector noise, suggesting that the approximately 1.3 cm thick shielding (a combination of titanium and beryllium) of the LOLA detectors is sufficient for SiAPDs on interplanetary missions with radiation environments similar to what the LRO experienced (559 cGy of radiation over 4 years).

Tackling excess noise from bilinear and nonlinear couplings in gravitational-wave interferometers

We describe a tool we improved to detect excess noise in the gravitational wave (GW) channel arising from its bilinear or nonlinear coupling with fluctuations of various components of a GW interferometer and its environment. We also describe a higher-order statistics tool we developed to characterize these couplings, e.g., by unraveling the frequencies of the fluctuations contributing to such noise, and demonstrate its utility by applying it to understand nonlinear couplings in Advanced LIGO engineering data. Once such noise is detected, it is highly desirable to remove it or correct for it. Such action in the past has been shown to improve the sensitivity of the instrument in searches of astrophysical signals. If this is not possible, then steps must be taken to mitigate its influence, e.g., by characterizing its effect on astrophysical searches. We illustrate this through a study of the effect of transient sine-Gaussian noise artifacts on a compact binary coalescence template bank.

Speech Enhancement Using Multi‐channel Post‐Filtering with Modified Signal Presence Probability in Reverberant Environment

In this paper, a multi-channel post-filtering approach in reverberant environment based on detection and estimation scheme is presented. A modified Signal presence probability (SPP), which is in consideration of reverberation, is proposed with a novel estimator Direct-toreverberate ratio (DRR) to adapt to distant-talking scene. SPP is known a key estimator to instruct the updating of transient noise or residual directional interference and form gain function in the time-frequency domain, consequently a new desired signal detection scheme is proposed to improve its accuracy. Appropriate spectral enhancement technique is applied to the noisy speech signal taking advantage of the modified SPP estimator. The proposed multi-channel post-filtering is tested in different nonstationary noisy and reverberant environments. Experimental results show that it achieves considerable improvement on signal preservation of the desired speech with more noise reduction over the comparative algorithms.

New application of wavelets in magnetotelluric data processing: reducing impedance bias

Magnetotelluric (MT) data consist of the sum of several types of natural sources including transient and quasiperiodic signals and noise sources (instrumental, anthropogenic) whose nature has to be taken into account in MT data processing. Most processing techniques are based on a Fourier transform of MT time series, and robust statistics at a fixed frequency are used to compute the MT response functions, but only a few take into account the nature of the sources. Moreover, to reduce the influence of noise in the inversion of the response functions, one often sets up another MT station called a remote station. However, even careful setup of this remote station cannot prevent its failure in some cases. Here, we propose the use of the continuous wavelet transform on magnetotelluric time series to reduce the influence of noise even for single site processing. We use two different types of wavelets, Cauchy and Morlet, according to the shape of observed geomagnetic events. We show that by using wavelet coefficients at clearly identified geomagnetic events, we are able to recover the unbiased response function obtained through robust remote processing algorithms. This makes it possible to process even single station sites and increase the confidence in data interpretation.

Noise Reduction Techniques and Scaling Effects towards Photon Counting CMOS Image Sensors

This paper presents an overview of the read noise in CMOS image sensors (CISs) based on four-transistors (4T) pixels, column-level amplification and correlated multiple sampling. Starting from the input-referred noise analytical formula, process level optimizations, device choices and circuit techniques at the pixel and column level of the readout chain are derived and discussed. The noise reduction techniques that can be implemented at the column and pixel level are verified by transient noise simulations, measurement and results from recently-published low noise CIS. We show how recently-reported process refinement, leading to the reduction of the sense node capacitance, can be combined with an optimal in-pixel source follower design to reach a sub- read noise at room temperature. This paper also discusses the impact of technology scaling on the CIS read noise. It shows how designers can take advantage of scaling and how the Metal-Oxide-Semiconductor (MOS) transistor gate leakage tunneling current appears as a challenging limitation. For this purpose, both simulation results of the gate leakage current and noise data reported from different foundries and technology nodes are used.

Acute effects of aircraft noise on cardiovascular admissions – an interrupted time-series analysis of a six-day closure of London Heathrow Airport caused by volcanic ash

Acute noise exposure may acutely increase blood pressure but the hypothesis that acute exposure to aircraft noise may trigger cardiovascular events has not been investigated. This study took advantage of a six-day closure of a major airport in April 2010 caused by volcanic ash to examine if there was a decrease in emergency cardiovascular hospital admissions during or immediately after the closure period, using an interrupted daily time-series study design. The population living within the 55dB(A) noise contour was substantial at 0.7 million. The average daily admission count was 13.9 (SD 4.4). After adjustment for covariates, there was no evidence of a decreased risk of hospital admission from cardiovascular disease during the closure period (relative risk 0.97 (95% CI 0.75–1.26)). Using lags of 1–7 days gave similar results. Further studies are needed to investigate if transient aircraft noise exposure can trigger acute cardiovascular events.

High mobility and high stability glassy metal-oxynitride materials and devices.

In thin film technology, future semiconductor and display products with high performance, high density, large area, and ultra high definition with three-dimensional functionalities require high performance thin film transistors (TFTs) with high stability. Zinc oxynitride, a composite of zinc oxide and zinc nitride, has been conceded as a strong substitute to conventional semiconductor film such as silicon and indium gallium zinc oxide due to high mobility value. However, zinc oxynitride has been suffered from poor reproducibility due to relatively low binding energy of nitrogen with zinc, resulting in the instability of composition and its device performance. Here we performed post argon plasma process on zinc oxynitride film, forming nano-crystalline structure in stable amorphous matrix which hampers the reaction of oxygen with zinc. Therefore, material properties and device performance of zinc oxynitride are greatly enhanced, exhibiting robust compositional stability even exposure to air, uniform phase, high electron mobility, negligible fast transient charging and low noise characteristics. Furthermore, We expect high mobility and high stability zinc oxynitride customized by plasma process to be applicable to a broad range of semiconductor and display devices.

A 12-bit 3.4 MS/s Two-Step Cyclic Time-Domain ADC in 0.18- CMOS

Two two-step cyclic time-domain analog-to-digital converters (TADCs) in a 0.18- $\mu \text{m}$ CMOS process are presented. The proposed TADC uses a voltage-to-time converter (VTC) with a 12-dB gain amplifier, and a time amplifier to achieve a 12-bit resolution. Only linear gain calibration is needed for the TADC. The first TADC achieves a spurious-free dynamic range (SFDR) of 70.5-dB and a signal-to-noise-plus distortion ratio (SNDR) of 64.3 dB. Its power consumption and area are 3 mW and 0.61 mm2, respectively. The noise analysis for each TADC building block is presented. The calculated results are verified by the transient noise analysis tool in HSPICE. To verify the noise analysis further, a second TADC is fabricated using the VTC with the device size scaled down by a factor of 4 based on the noise analysis. The second TADC achieves an SFDR of 66.8 dB and an SNDR of 59.1 dB. Its power consumption and area are 2.9 mW and 0.61 mm2, respectively.

Data‐adaptive detection of transient deformation in geodetic networks

AbstractThe recent development of dense and continuously operating Global Navigation Satellite System (GNSS) networks worldwide has led to a significant increase in geodetic data sets that sometimes capture transient‐deformation signals. It is challenging, however, to extract such transients of geophysical origin from the background noise inherent to GNSS time series and, even more so, to separate them from other signals, such as seasonal redistributions of geophysical fluid mass loads. In addition, because of the very large number of continuously recording GNSS stations now available, it has become impossible to systematically inspect each time series and visually compare them at all neighboring sites. Here we show that Multichannel Singular Spectrum Analysis (M‐SSA), a method derived from the analysis of dynamical systems, can be used to extract transient deformations, seasonal oscillations, and background noise present in GNSS time series. M‐SSA is a multivariate, nonparametric, statistical method that simultaneously exploits the spatial and temporal correlations of geophysical fields. The method allows for the extraction of common modes of variability, such as trends with nonconstant slopes and oscillations shared across time series, without a priori hypotheses about their spatiotemporal structure or their noise characteristics. We illustrate this method using synthetic examples and show applications to actual GPS data from Alaska to detect seasonal signals and microdeformation at the Akutan active volcano. The geophysically coherent spatiotemporal patterns of uplift and subsidence thus detected are compared to the results of an idealized model of such processes in the presence of a magma chamber source.

A transient noise simulation model for the analysis of the optimal number of stages of the analog accumulator in TDI CMOS image sensors

In this paper, a fast transient noise simulation model is proposed to analyze the optimal number of stages for the maximum signal to noise ratio (SNR) of the analog accumulator in a fixed silicon area. The Transient Noise Simulation (TNS) is required to confirm the analysis of the optimal number of stages, which requires long simulation time. In order to accelerate our analysis, a fast transient noise simulation model (TNSM) is proposed based on the noise analysis and shown to be effective by TNS. Numerical analysis is verified by the TNSM, and it indicates that the optimal number of stages in a fixed area changes with the noise of the input signal.

Leveraging waveform complexity for confident detection of gravitational waves

The recent completion of Advanced LIGO suggests that gravitational waves (GWs) may soon be directly observed. Past searches for gravitational-wave transients have been impacted by transient noise artifacts, known as glitches, introduced into LIGO data due to instrumental and environmental effects. In this work, we explore how waveform complexity, instead of signal-to-noise ratio, can be used to rank event candidates and distinguish short duration astrophysical signals from glitches. We test this framework using a new hierarchical pipeline that directly compares the Bayesian evidence of explicit signal and glitch models. The hierarchical pipeline is shown to have strong performance, and in particular, allows high-confidence detections of a range of waveforms at realistic signal-to-noise ratio with a two detector network.

Automated detection of latency tracks in microneurography recordings using track correlation

BackgroundThe marking technique in microneurography uses stimulus-induced changes in neural conduction velocity to characterize human C-fibers. Changes in conduction velocity are manifested as variations in the temporal latency between periodic electrical stimuli and the resulting APs. When successive recorded sweeps are displayed vertically in a “waterfall” format, APs correlated with the stimulus form visible vertical tracks. Automated detection of these latency tracks is made difficult by sometimes poor signal-to-noise ratio in recordings, spontaneous neural firings uncorrelated with the stimuli, and multi-unit recordings with crossing or closely parallel tracks. New methodWe developed an automated track-detection technique based on a local linearization of the latency tracks of stimulus-correlated APs. This technique enhances latency tracks, eliminates transient noise spikes and spontaneous neural activity not correlated with the stimulus, and automatically detects latency tracks across successive sweeps in a recording. ResultsWe evaluated our method on microneurography recordings showing varying signal quality, spontaneous firing, and multiple tracks that run closely parallel and cross. The method showed excellent detection of latency tracks in all of our recordings. Comparison with existing method(s)We compare our method to the commonly used track detection method of Hammarberg as implemented in the Drever program. ConclusionsOur method is a robust means of automatically detecting latency tracks in typical microneurography recordings.

Compact Modeling of Phase-Locked Loop Frequency Synthesizer for Transient Phase Noise and Jitter Simulation

Compact modeling of phase-locked loop (PLL) frequency synthesizer is proposed to reduce transient phase noise and jitter simulation time. Conventional small-signal noise assumption based frequency-domain simulation approach produces inaccurate results for nonlinear PLLs. Accurate analysis of nonlinear PLL are possible through time-domain, or transient noise simulation but time-domain simulation is computation-intensive and time-consuming. This paper presents a practical solution for transient phase noise and jitter analysis using compact modeling techniques. It features an autoregressive moving average process modeled voltage-controlled oscillator with fractional calculus and wavelet transform for phase noise decomposition and reconstruction, thereby reducing the phase noise and jitter simulation time to 25.8% of the transistor-level simulation with 0.4 dB @ 1 MHz phase noise error and 0.3 ps long-term jitter error for a 2 GHz PLL frequency synthesizer in a 65 nm CMOS process.

減衰比を指標としたヘルムホルツ共鳴器の設計法

Helmholtz resonators are used in many industrial products as devices for reducing low-frequency noise. An advantage of the Helmholtz resonator is that the structure is simple and applicable to low-frequency noise for its size. Further, an important feature is that the development costs and product costs are relatively low in actual product development. The optimum combination of the natural frequency and modal damping ratio of a Helmholtz resonator is dependent on the characteristic of the noise source. It is selected so as to minimize the sound pressure levels when the noise is stationary. In the case of a transient noise problem, the natural frequency and modal damping ratio is tuned for maximizing the modal damping ratios of the system consisting of the main system and a Helmholtz resonator. Noise reduction effects of Helmholtz resonators are generally predicted by 3D acoustic analysis. Recently, the effects are estimated by CFD at higher sound pressure levels exceeding 100dB, because they are greatly affected by eddies generated in the neck portion of resonators. However, there is no suitable method to predict the noise reduction effects of Helmholtz resonators that engineers can use easily in the early stages of design. This paper describes a simple method for estimating the optimum value of modal damping ratios of the acoustic system having a Helmholtz resonator. Here, two-degrees-of-freedom models similar to the mass-spring-damper models used in the design of tuned mass dampers are used. In addition, the differences between the optimum conditions of tuned mass dampers and Helmholtz resonators are described.

MOSFET gate induced time domain noise simulation accuracy benchmarking

Analysis of MOSFET gate induced transient noise simulation accuracy was performed and the limitation on accurately estimating MOSFET noise performance in the high frequency wireless communications region was identified, validating transient noise simulation against AC noise. The gate noise source is the only one that increases with frequency and this behaviour cannot be simulated accurately using SPECTRE/RF. To enable the design community to accurately simulate gate induced noise in nonlinear circuits, a simple and practical methodology to overcome this limitation is provided, using a highpass filtering-based white noise source approach.

自由振動と強制振動におけるヘルムホルツ共鳴器の最適減衰比の検討

Helmholtz resonators are used in many industrial products as devices for reducing low-frequency noise. An advantage of the Helmholtz resonator is that the structure is simple and applicable to low-frequency noise for its size. Further, an important feature is that the development costs and product costs are relatively low in actual product development. The optimum combination of the natural frequency and modal damping ratio of a Helmholtz resonator is dependent on the characteristic of the noise source. It is selected so as to minimize the sound pressure levels when the noise is stationary. In the case of a transient noise problem, the natural frequency and modal damping ratio is tuned for maximizing the modal damping ratios of the system consisting of the main system and a Helmholtz resonator. Noise reduction effects of Helmholtz resonators are generally predicted by 3D acoustic analysis. Recently, the effects are estimated by CFD at higher sound pressure levels exceeding 100dB, because they are greatly affected by eddies generated in the neck portion of resonators. However, there is no suitable method to predict the noise reduction effects of Helmholtz resonators that engineers can use easily in the early stages of design. This paper describes a simple method for estimating the optimum value of modal damping ratios of the acoustic system having a Helmholtz resonator. Here, two-degrees-of-freedom models similar to the mass-spring-damper models used in the design of tuned mass dampers are used. In addition, the difference between the optimum condition of the maximization problem of modal damping ratios and the minimization problem of sound pressure levels are described.

Research on Speech Enhancement Algorithm Based on EMD in Noisy Environments

This paper presents a new technique for speech enhancement in a noisy environment based on the empirical mode decomposition (EMD) algorithm and spectral subtraction. With the EMD, the noise speech signals can be decomposed into a sum of the band-limited function called intrinsic mode functions (IMFs), which is a zero-mean AM-FM component. Then spectral subtraction of the IMF components with noise can be used to eliminate the effect of the noise for speech enhancement. Experimental results demonstrate the advantage of using the proposed simultaneous detection and estimation approach with the proposed algorithm, which facilitate suppression of transient noise with a controlled level of speech distortion.

Managing Test Coverage Uncertainty due to Random Noise in Nano-CMOS: A Case-Study on an SRAM Array

Static random access memories (SRAM) are a major constituent in high performance microprocessors and systems-on-a-chip. With scaling of technology, manufacturing process variations in SRAMs are of significant concern. SRAM cells that are marginal due to process variations suffer from stability issues where random thermal noise and random telegraph noise (RTN) become determinant in memory state. This introduces uncertainty in testing, where passing a test does not necessarily mean that SRAM is good. A marginal cell may pass testing, but fail during operation. To address this problem, we introduce a new metric for probabilistic fault coverage. We present simulation methods for measuring such coverage and propose N-detect and multilevel wordline (WL) voltage techniques to increase the detection probability of marginal cells. We demonstrate the benefit of these testing approaches on a sample SRAM array, designed in 32 nm predictive technology models. To simulate marginal cells, we oversample the tail of the process variations distribution. Transient noise simulations show that thermal noise can lead to a fault coverage loss of 20% and RTN can lead to a maximum fault coverage loss of up to 75%. N-detect technique achieves close to a 100% fault coverage at ${n}\,\, {=} 100$ for thermal noise and ${n}\,\,{=} 70$ for RTN. Multilevel WL technique requires 20–30 mV boost in WL voltage during read test to achieve near ideal fault coverage at minimal yield loss. A combination of these techniques is shown to be effective in increasing fault coverage with a tradeoff between test time and yield loss.