Narrow-band Noise Research Articles

Modelling impulsive noise in indoor powerline communication systems

Powerline communication (PLC) is an emerging technology that has an important role in smart grid systems. Due to making use of existing transmission lines for communication purposes, PLC systems are subject to various noise effects. Among those, the most challenging one is the impulsive noise compared to the background and narrowband noise. In this paper, we present a comparative study on modelling the impulsive noise amplitude in indoor PLC systems by utilising several impulsive distributions. In particular, as candidate distributions, we use the symmetric alpha -Stable (Salpha S), generalised Gaussian, Bernoulli Gaussian and Student’s t distribution families as well as the Middleton Class A distribution, which dominates the literature as the impulsive noise model for PLC systems. Real indoor PLC system noise measurements are investigated for the simulation studies, which show that the Salpha S distribution achieves the best modelling success when compared to the other families in terms of the statistical error criteria, especially for the tail characteristics of the measured data sets.

Installation and Performance of the Albuquerque Seismological Laboratory Small-Aperture Posthole Array

AbstractThe Global Seismographic Network (GSN) has been used extensively by seismologists to characterize large earthquakes and image deep earth structure. Although the network’s original design goals have been met, the seismological community has suggested that the incorporation of small-aperture seismic arrays at select sites may improve performance of the network and enable new observations. As a pilot study for this concept, we have created a 500 m aperture, nine-element broadband seismic array around the GSN station ANMO (Albuquerque, New Mexico) at the U.S. Geological Survey Albuquerque Seismological Laboratory (ASL). The array was formed by supplementing the secondary borehole seismometer (90 m depth) at ANMO with eight additional 2.6 m posthole sites. Each station’s seismometer was oriented using a fiber optic gyroscope to within 2.0° of north. Data quality, particularly on the vertical components, is excellent with median power levels closely tracking the secondary sensor at ANMO at frequencies lower than 1 Hz. Horizontal component data are more variable at low frequencies (<0.02 Hz), with the type of installation and local geography appearing to strongly influence the amount of tilt-induced noise. Throughout the article, we pose several fundamental questions related to the variability and precision of seismic wavefield measurements that we seek to address with data from this array. In addition, we calculate the array response and show a few examples of using the array to obtain back azimuths of a local event and a continuous narrowband noise source. The apparent velocity of the event across the array is then used to infer the local P-wave velocity at the ASL. Near-real-time data collected from the array along with collocated meteorological, magnetic, and infrasound data are freely available in near-real time from the Incorporated Research Institutions for Seismology Data Management Center.

Spatial specificity in attentional modulation of prepulse inhibition of the startle reflex in rats.

Prepulse inhibition (PPI), the suppression of the startle reflex when the startling stimulus is shortly preceded by a weaker non-startling sensory stimulus (prepulse), can be enhanced by selective attention to the prepulse with a marked prepulse-feature specificity. To determine if the attentional modulation of PPI in rats can also be perceptual location specific, this study investigated whether fear-conditioning of a prepulse perceived at a location can enhance PPI only when the conditioned prepulse is perceived at that conditioned location. A continuous narrowband noise (NBN) was delivered by each of the two spatially separated loudspeakers in the frontal azimuth with a silent gap embedded in each NBN. The inter-loudspeaker interval was 1ms (either left or right loudspeaker leading). Due to the precedence effect, both the NBN and gap images were perceived at the leading loudspeaker. The perceptually fused gap was used as the prepulse. To fear-condition one gap prepulse, which was perceived at one loudspeaker, the prepulse was paired with footshock in a temporally precise manner and the other gap (the conditioning-control prepulse) perceived at the other (opposite) loudspeaker was paired with footshock in a random manner. Compared to PPI before conditioning, PPI induced by the fear-conditioned gap perceived at the fear-conditioned loudspeaker, but not that by the conditioning-control gap, was significantly enhanced. Thus, attentional modulation of PPI can be not only prepulse-feature specific, but also perceptual location specific, and involves combined central processes for content and location information.

Cortical Activation Patterns of Different Masking Noises and Correlation With Their Masking Efficacy, Determined by Functional Near-Infrared Spectroscopy.

Acoustic therapy in tinnitus treatment is poorly characterized, and efficacy assessment depends on subjective descriptions. Narrow-band noise, notched sound, and white noise have positive therapeutic effects on monotonous tinnitus. Considering the tonotopic characteristics of the auditory system and the spectral characteristics of these three masking sounds, the activation pattern of the auditory cortex and the mechanism of inhibiting tinnitus may be different. This study aimed to compare the activation patterns of three spectrally different masking noises and study the correlation between the masking effects and variational amplitude of oxygenated hemoglobin (HbO) in the corresponding cortical regions. We also assessed near-infrared spectroscopy brain function imaging (NIRS) as an objective assessment tool in acoustic therapy. Patients with persistent non-pulsatile tinnitus and control volunteers without tinnitus were enrolled in this study. The subjects were seated in a sound-proof room, with two optode arrays covering the bilateral temporal lobe. Auditory stimuli were presented; stimulation sequences followed the block design: different noises appeared randomly and repeated in five cycles. Tinnitus match and residual inhibition were performed in the tinnitus group. The data analyses were conducted using the NIRS_SPM toolbox. The group analysis results showed that the narrow-band noise caused a marginally significant decrease in HbO signal in the Brodmann 21 region (BA21), while white noise caused a significant increase in HbO signal in BA21. Notched sound did not cause significant changes in the HbO signal in the temporal cortex. And none of the three masking noises caused significant changes in the HbR signal in the temporal cortex. The depth of residual inhibition induced by the narrow-band noise and white noise significantly correlated with ΔHbO in the region of interest (ROI). However, neither the depth nor duration of the residual inhibition induced by notched sound correlated with the ΔHbO. Thus, NIRS showed three cortical activation patterns induced by three different masking noises, and correlations between residual inhibition effects and change of HbO amplitude were found. NIRS could therefore be applied in objective assessment of acoustic therapy.

High-frequency current oscillations in charge-density-wave 1T-TaS2 devices: Revisiting the “narrow band noise” concept

We report on the current oscillations in quasi-2D 1T-TaS2 charge-density-wave two-dimensional devices. The MHz-frequency range of the oscillations and the linear dependence of the frequency of the oscillations on the current closely resemble the narrow band noise, which was often observed in the classical bulk quasi-1D trichalcogenide charge-density-wave materials. In bulk quasi-1D materials, the narrow band noise was interpreted as direct evidence of charge-density-wave sliding. Despite the similarities, we argue that the nature of the MHz oscillations in 1T-TaS2 is different from the narrow band noise. Analysis of the biasing conditions and current indicates that the observed oscillations are related to the current instabilities due to the voltage-induced transition from the nearly commensurate to incommensurate charge-density-wave phase.

Improving the frequency response of Savitzky-Golay filters via colored-noise models

Savitzky-Golay (SG) filters are finite impulse response (FIR) realizations of least-squares polynomial regression and they are widely used for filtering (e.g. smoothing, interpolating, predicting, differentiating) and processing (e.g. detecting and classifying) non-stationary signals in non-Gaussian noise. For such inputs, the Wiener filter is biased and the Kalman filter is sub-optimal. Sequentially-correlated (i.e. ‘colored’) noise models are an integral part of the Wiener filter and an optional addition to the Kalman filter; however, their use in SG-filters has been overlooked in recent times. It is shown here that colored (wide-band and narrow-band) noise models are readily incorporated into a standard SG-filter and that this also addresses the well-known deficiency of their poor frequency-selectivity/configurability. A wide-band noise model sets the main-lobe/side-lobe width/height and provides physical justification for band-limited design procedures described elsewhere. The proposed narrow-band noise model, with arbitrarily placed side-lobe nulls, has the potential to outperform other SG filters when sinusoidal interferers of known frequency are present. The utility of these ‘whitened’ SG-filters is illustrated in a hypothetical pulse/peak-detection application using a test statistic that is shaped by the noise model.

A Mouse Model of Tinnitus Using Gap Prepulse Inhibition of the Acoustic Startle in an Accelerated Hearing Loss Strain.

To develop a mouse model for temporary and persistent tinnitus using the gap startle paradigm. Behavioral animal models for tinnitus are classified into conditioning- and reflex-based types. Gap prepulse inhibition of the acoustic startle (GPIAS) is based on the acoustic startle modification by a silent gap and gap detection deficit caused by tinnitus gap filling. We used C57BL/6J mice inherently susceptible to hearing loss and potentially predisposed to tinnitus. They were divided into the control, salicylate-induced tinnitus, and noise-induced tinnitus groups. Mice were tested with the auditory brainstem response at four frequencies (8, 16, 24, and 32 kHz) and GPIAS in three carrier conditions, 16 and 24 kHz narrow band noises (NBNs) and broadband noise, at multiple time points before and after treatment. The ratio between the gap startle and no-gap startle amplitudes was analyzed by a repeated measures design. In addition, the number of tinnitus-positive mice meeting a specified criterion was counted. Salicylate/unilateral noise trauma resulted in temporary/permanent tinnitus evidenced by GPIAS reduction. GPIAS reduction was the most significant at 16 kHz NBN among the three carriers in both tinnitus groups. Control mice also showed good gap detection performance at 16 kHz NBN, which is in the most sensitive hearing range in mice. The GPIAS test in C57BL/6J mice was very reliable at 16 kHz NBN. This tinnitus model developed in the mouse strain of accelerated hearing loss can be used with two options of temporary and persistent tinnitus.

Study the Passage of a Mixture of Radio Impulse and Narrow-Band Noise through Frequency Detector

Study the Passage of a Mixture of Radio Impulse and Narrow-Band Noise through Frequency Detector

Acoustic metamaterial capsule for reduction of stage machinery noise

Noise mitigation of stage machinery can be quite demanding and requires innovative solutions. In this work, an acoustic metamaterial capsule is proposed to reduce the noise emission of several stage machinery drive trains, while still allowing the ventilation required for cooling. The metamaterial capsule consists of c-shape meta-atoms, which have a simple structure that facilitates manufacturing. Two different metamaterial capsules are designed, simulated, manufactured, and experimentally validated that utilize an ultra-sparse and air-permeable reflective meta-grating. Both designs demonstrate transmission loss peaks that effectively suppress gear mesh noise or other narrow band noise sources. The ventilation by natural convection was numerically verified, and was shown to give adequate cooling, whereas a conventional sound capsule would lead to overheating. The noise spectra of three common stage machinery drive trains are numerically modelled, enabling one to design meta-gratings and determine their noise suppression performance. The results fulfill the stringent stage machinery noise limits, highlighting the benefit of using metamaterial capsules of simple c-shape structure.

Method for Estimating the Latent Correlation of Narrowband Noise Signals

The concept of hidden correlation of noise signals is introduced. Theoretically, the existence of a hidden correlation between narrow-band noise signals extracted simultaneously from a broadband band-limited noise is proved. A method for estimating the latent correlation of narrow-band noise signals has been developed and experimentally investigated. An experiment was conducted where a temporal fragment of band-limited noise was used as the signal under investigation, the basis of which is shot noise. It was found that when applying the Pearson criterion between the signal at the center frequency and the sum of the signals at the mirror frequencies, virtually no correlation is found, and when using the proposed method for analyzing the same signals, a strong hidden correlation is found. The proposed method is useful for specialists involved in digital signal processing, as well as developers of measuring tools using a new technology for extracting a useful signal from noise – the method of mirror noise images.

Identifying cues for tone-in-noise detection using decision variable correlation in the budgerigar (Melopsittacus undulatus).

Previous studies evaluated cues for masked tone detection using reproducible noise waveforms. Human results founded on this approach suggest that tone detection is based on combined energy and envelope (ENV) cues, but detection cues in nonhuman species are less clear. Decision variable correlation (DVC) was used to evaluate tone-in-noise detection cues in the budgerigar, an avian species with human-like behavioral sensitivity to many complex sounds. DVC quantifies a model's ability to predict trial-by-trial variance in behavioral responses. Budgerigars were behaviorally conditioned to detect 500-Hz tones in wideband (WB; 100-3000 Hz) and narrowband (NB; 452-552 Hz) noise. Behavioral responses were obtained using a single-interval, two-alternative discrimination task and two-down, one-up adaptive tracking procedures. Tone-detection thresholds in WB noise were higher than human thresholds, putatively due to broader peripheral frequency tuning, whereas NB thresholds were within ∼1 dB of human results. Budgerigar average hit and false-alarm rates across noise waveforms were consistent, highly correlated across subjects, and correlated to human results. Trial-by-trial behavioral results in NB noise were best explained by a model combining energy and ENV cues. In contrast, WB results were better predicted by ENV-based or multiple-channel energy detector models. These results suggest that budgerigars and humans use similar cues for tone-in-noise detection.

Research on Partial Discharge De-Noising for Transformer Based on Synchro-Squeezed Continuous Wavelet Transform

Traditional time-frequency methods for partial discharge (PD) de-noising have some limitations such as low time-frequency resolution, single de-noising type and poor readability. In this paper, a novel de-noising algorithm based on synchro-squeezed continuous wavelet transform (CWT) is adopted to filter out narrowband noise and white noise. The synchro-squeezed CWT algorithm is designed to redistribute the time-frequency domain and to distinguish the signal from the noise carefully as a high-rate time-frequency analysis. High-order statistics is employed to pre-process the polluted PD signal. The generalized cross-validation (GCV) threshold is combined with the adaptive trimmed threshold of synchro-squeezing (SS) domain to deal with the subsequent signals. The proposed algorithm can effectively suppress two kinds of noise, and the signal distortion is lower.

Altered functional connectivity of the thalamus in tinnitus patients is correlated with symptom alleviation after sound therapy.

Altered functional connectivity (FC) of the thalamus has been proven to be an important finding in tinnitus patients. Tinnitus can be effectively desensitized by sound therapy. However, it is still unclear whether and how sound therapy affects the FC of the thalamus. Resting-state functional magnetic resonance imaging data and anatomical data were longitudinally collected from 25 idiopathic tinnitus patients before and after 12weeks of sound therapy by using adjusted narrow band noise and from 25 matched healthy controls at the same time interval without any intervention. The FC of bilateral thalami were analyzed by setting the left and right thalamus as the regions of interest. Significant main effect of group on the FC of the thalamus were found mainly in the key components of the default mode network, limbic network, salience network, cognitive control network, auditory network and occipital region. FC values between the thalamus, inferior frontal gyrus (IFG), and anterior cingulate cortex (ACC) featured higher values in the tinnitus group at baseline compared to the healthy controls and restoration in tinnitus patients after treatment. Decreased Tinnitus Handicap Inventory (THI) scores and decreased FC values between the right thalamus and right IFG were positively correlated (r = 0.476, P = 0.016). Abnormal FC of the thalamus is associated with multiple brain networks. Sound therapy has a normalizing effect on the enhanced FC of the thalamus-IFG and thalamus-ACC, representing decreased tinnitus attention control and less involvement of the noise-canceling system.

Leak Location Based on PDS-VMD of Leakage-Induced Vibration Signal Under Low SNR in Water-Supply Pipelines

Leak location in water-supply pipelines is of great significance in order to preserve water resources and reduce economic losses. Cross-correlation (CC) based leak location is a popular and effective method in water-supply pipelines (WSP). However, with a decrease of signal to noise ratio (SNR), the errors of time-delay estimation (TDE) based on CC will become larger making it almost impossible to determine a leakage position. Hence, this work proposes leak location based on a combination of phase difference spectrum and variational mode decomposition (PDS-VMD) of leakage-induced vibration signal under low SNR for WSP. Firstly, the leakage-induced vibration signal is decomposed into several intrinsic mode functions (IMFs) by VMD, where the characteristic frequency band is determined by PDS of cross spectrum of two leakage signals. Then, the energy ratio of leakage signal in characteristic frequency band serves as a guideline to select effective IMF components from the decomposed IMFs. Finally, the selective IMFs are reconstituted into a new signal which can be used to determine a leak position using CC based TDE. In order to verify the effectiveness of the proposed leak location algorithm, the method based on PDS-VMD is compared with that using CC, combination of CC coefficient and VMD (CCC-VMD) using both simulation and experiment. The simulation and experimental results demonstrate that the proposed PDS-VMD method is more suitable for leak location in WSP, which provides immunity to both broadband and narrow band noise under low SNR.

Objective Verification of Acute Tinnitus and Validation of Efficacy of Systemic Steroids in Rats.

BackgroundThis study was performed to identify acute tinnitus and evaluate the efficacy of steroids for noise-induced acute tinnitus by measuring the gap-prepulse inhibition of the acoustic startle (GPIAS) value in an animal model.MethodsNineteen rats (the noise group [n = 7] and the noise + dexamethasone [DEX] group [n = 12]) were exposed to narrow-band noise centered at 16 kHz from a sound generator for 4 hours. The noise + DEX group received intraperitoneal steroid administration daily for 5 days (1.5 mg/kg/day) after completing noise exposure. Auditory brainstem response and GPIAS value were measured just prior to, and 1 day after noise exposure and on days 1 and 10 days after completing steroid administration. The changes in cochlear structure were evaluated by histological analysis.ResultsThe threshold shift was checked 1 and 10 days after intraperitoneal steroid injection, and no differences in threshold shift were observed between the two groups in each frequency except for 32 kHz 1 day after steroid injection. The mean GPIAS value in the noise + DEX group (36.4% ± 14.1%) was significantly higher than that in the noise group (16.4% ± 18.8%) 10 days after intraperitoneal steroid administration (P = 0.017). There were no pathological changes associated with noise trauma in the two groups as determined on hematoxylin and eosin and immunohistochemical staining.ConclusionAn acute tinnitus model with minimal structural changes by noise exposure was set up, and used to verify tinnitus objectively by measuring the GPIAS value. Steroid therapy for control of tinnitus was validated in this animal model.

An Efficient Narrowband Active Noise Control System for Accommodating Frequency Mismatch

The conventional narrowband active noise control (ANC) is a popular method for reducing narrowband noise generated from rotating machines like engines, fans, blowers, and power transformers. The narrowband active noise control works efficiently only when the internal reference frequency of the controller and the frequency of the primary noise remains the same. Any change in the frequency of the primary noise from that of the reference is termed as frequency mismatch (FM), which degrades the narrowband ANC performance. In this paper, a filtered-x weighted-frequency Fourier linear combiner least mean square (FX-WFLC-LMS) algorithm is developed for narrowband ANC system. This algorithm is capable of adapting to both frequency and amplitude variations in the primary noise. To reduce the computational burden of the proposed FX-WFLC-LMS algorithm, a computationally efficient filtered-error weighted-frequency Fourier linear combiner least mean square (FE-WFLC-LMS) algorithm is also proposed. The comparative performance of these proposed algorithms is evaluated through extensive simulation and real-time experiments. It was found that both these proposed algorithms are capable of correcting any amount of frequency mismatch and are suitable for narrowband ANC systems.

Disparity in interaural time difference improves the accuracy of neural representations of individual concurrent narrowband sounds in rat inferior colliculus and auditory cortex.

The central mechanisms underlying binaural unmasking for spectrally overlapping concurrent sounds, which are unresolved in the peripheral auditory system, remain largely unknown. In this study, frequency-following responses (FFRs) to two binaurally presented independent narrowband noises (NBNs) with overlapping spectra were recorded simultaneously in the inferior colliculus (IC) and auditory cortex (AC) in anesthetized rats. The results showed that for both IC FFRs and AC FFRs, introducing an interaural time difference (ITD) disparity between the two concurrent NBNs enhanced the representation fidelity, reflected by the increased coherence between the responses evoked by double-NBN stimulation and the responses evoked by single NBNs. The ITD disparity effect varied across frequency bands, being more marked for higher frequency bands in the IC and lower frequency bands in the AC. Moreover, the coherence between IC responses and AC responses was also enhanced by the ITD disparity, and the enhancement was most prominent for low-frequency bands and the IC and the AC on the same side. These results suggest a critical role of the ITD cue in the neural segregation of spectrotemporally overlapping sounds.NEW & NOTEWORTHY When two spectrally overlapped narrowband noises are presented at the same time with the same sound-pressure level, they mask each other. Introducing a disparity in interaural time difference between these two narrowband noises improves the accuracy of the neural representation of individual sounds in both the inferior colliculus and the auditory cortex. The lower frequency signal transformation from the inferior colliculus to the auditory cortex on the same side is also enhanced, showing the effect of binaural unmasking.

Index modulation aided multi carrier power line communication employing rank codes from cyclic codes

In a multi-carrier power line communication (mPLC) with dominant Narrowband and Impulse noise, crisscross errors can be clearly observed. In this work, mPLC employing Rank codes with Index modulation (mPLC-IM) has been considered to provide a reliable high data rate communication over the powerline channel. The rank codes required for this implementation have been derived from cyclic codes over GF(qm) viewed as m×n matrices over GF(q). Encoding has been performed by employing the Galois Field Fourier Transform (GFFT) domain description of cyclic codes. This scheme is able to correct a variety of crisscross errors in mPLC-IM The GFFT approach provides an additional degree of freedom that is offered by choice of free transform component indices. It can be used to design an index key scheme which can enhance the physical layer security of an mPLC system. In the absence of knowledge of the index key, it is observed that the probability of error reaches an error floor of ≈10−2, highlighting the need for index key for appropriate decoding. Further, a novel check matrix construction is proposed and used in devising a decoding strategy. It is observed that the proposed decoder is capable of correcting any errors of rank ≤⌊m−12⌋. In mPLC-IM with OFDM, the proposed codes over GF(24) provide an asymptotic gain of approximately 3 dB when compared to the uncoded system. For mPLC-IM with multi-tone Frequency Shift Keying (FSK), the proposed RC over GF(24) provides a 25% improvement in symbol error rate (SER) at lower values of p (probability of occurrence of narrowband noise) when compared to Reed-Solomon (RS) based Constant Weight (CW) CW(13,6,5)2∘RS[15,14,2]16 codes. Further, a SER improvement of around 30% is achieved using rank codes (RCs) over GF(28) when compared with CW(9,4,4)2∘RS[15,14,2]16. In the presence of dominant background noise, the BER graphs show that the proposed codes are equivalent (slightly superior) in performance as that of Low Rank Parity Check (LRPC)/Gabidulin based designs. In the presence of dominant impulse noise, the proposed system is providing significant gain when compared with the Linearly Pre-coded Orthogonal Frequency Division Multiplexing (LP-OFDM) system and LRPC based scheme. Additionally, simulation results show that, in the absence of an index key, the probability of error reaches the error floor, highlighting the need for index key for appropriate decoding. This can be viewed as the code capable of providing an additional layer of security.

Dynamic properties of a one-dimensional charge density wave compound in the presence of uncondensed-carriers: Insights from numerical experiences

In the present Letter, a numerical study of the dynamic properties of one-dimensional (1D) incommensurate charge density wave (CDW) compound in the presence of free carriers (not affected by the Peierls transition) is carried out. The results obtained showed that the CDW sliding state is very sensitive to this local effect. The CDW depinning threshold field, excess current normalized and amplitude of Narrow-Band-Noise (NBN) are affected by these single particle’s excitations. This latter can be viewed as a screening effect of the applied electrical field by free carriers which relax in order to reduce the CDW polarization and generate a homogeneous system response.

Human Auditory Detection and Discrimination Measured with the Pupil Dilation Response

In the standard Hughson-Westlake hearing tests (Carhart and Jerger 1959), patient responses like a button press, raised hand, or verbal response are used to assess detection of brief test signals such as tones of varying pitch and level. Because of its reliance on voluntary responses, Hughson-Westlake audiometry is not suitable for patients who cannot follow instructions reliably, such as pre-lingual infants (Northern and Downs 2002). As an alternative approach, we explored the use of the pupillary dilation response (PDR), a short-latency component of the orienting response evoked by novel stimuli, as an indicator of sound detection. The pupils of 31 adult participants (median age 24 years) were monitored with an infrared video camera during a standard hearing test in which they indicated by button press whether or not they heard narrowband noises centered at 1, 2, 4, and 8 kHz. Tests were conducted in a quiet, carpeted office. Pupil size was summed over the first 1750 ms after stimulus delivery, excluding later dilations linked to expenditure of cognitive effort (Kahneman and Beatty 1966; Kahneman et al. 1969). The PDR yielded thresholds comparable to the standard test at all center frequencies tested, suggesting that the PDR is as sensitive as traditional methods of assessing detection. We also tested the effects of repeating a stimulus on the habituation of the PDR. Results showed that habituation can be minimized by operating at near-threshold stimulus levels. At sound levels well above threshold, the PDR habituated but could be recovered by changing the frequency or sound level, suggesting that the PDR can also be used to test stimulus discrimination. Given these features, the PDR may be useful as an audiometric tool or as a means of assessing auditory discrimination in those who cannot produce a reliable voluntary response.