Impulse noise

About: Impulse noise is a research topic. Over the lifetime, 4816 publications have been published within this topic receiving 63970 citations.

Landsat-7 ETM+ on-orbit reflective-band radiometric characterization

Abstract: The Landsat-7 Enhanced Thematic Mapper Plus (ETM+) has been and continues to be radiometrically characterized using the Image Assessment System (IAS), a component of the Landsat-7 Ground System Key radiometric properties analyzed include: overall, coherent, and impulse noise; bias stability; relative gain stability; and other artifacts The overall instrument noise is characterized across the dynamic range of the instrument during solar diffuser deployments Less than 1% per year increases are observed in signal-independent (dark) noise levels, while signal-dependent noise is stable with time Several coherent noise sources exist in ETM+ data with scene-averaged magnitudes of up to 04 DN, and a noise component at 20 kHz whose magnitude varies across the scan and peaks at the image edges Bit-flip noise does not exist on the ETM+ However, impulse noise due to charged particle hits on the detector array has been discovered The instrument bias is measured every scan line using a shutter Most bands show less than 01 DN variations in bias across the instrument lifetime The panchromatic band is the exception, where the variation approaches 2 DN and is related primarily to temperature The relative gains of the detectors, ie, each detector's gain relative to the band average gain, have been stable to /spl plusmn/01% over the mission life Two exceptions to this stability include band 2 detector 2, which dropped about 1% in gain about 35 years after launch and stabilized, and band 7 detector 5, which has changed several tenths of a percent several times since launch Memory effect and scan-correlated shift, a hysteresis and a random change in bias between multiple states, respectively, both of which have been observed in previous Thematic Mapper sensors, have not been convincingly found in ETM+ data Two artifacts, detector ringing and "oversaturation", affect a small amount of ETM+ data

Nonauditory injury threshold for repeated intense freefield impulse noise.

Abstract: Exposure to impulse noise is an important occupational health concern. The risk of injury to auditory structures is well recognized and provides the cornerstone for present safety standards. For freefield impulse noise, nonauditory injury is dependent on peak pressure, positive phase duration (or impulse), and number of exposures. Trivial laryngeal petechiae are shown to precede nonauditory injury to more critical organs (ie, pulmonary and gastrointestinal systems). This study identifies the critical impulse noise thresholds causing trivial laryngeal petechial changes resulting from exposure to 5, 25, and 100 repetitions of specific levels of impulse noise. Because of anatomical differences, sheep should be slightly more susceptible to impulse noise laryngeal petechial changes than man; therefore, it seems reasonable to set the absolute limits for human occupational exposure levels below those causing laryngeal petechiae in sheep for persons wearing adequate hearing protection. This study does not address human auditory injury that may occur above or below these exposure limits even with proper hearing protection.

A novel approach for suppression of powerline interference and impulse noise in ECG signals

Abstract: One of the major problems encountered in recording ECG is the appearance of unwanted distortions induced by power line interference in the electrocardiogram. In addition, infections due to impulse noise leads to variations in the amplitudes which represent the abnormalities associated with the heart. This paper proposes a novel approach for addressing both the aforementioned issues in ECG signals employing sub-band decomposition using wavelets analysis. Morphological filtering is applied to the detail sub-bands for removal of impulse noise using one-dimensional structuring element. Further, the powerline interference is removed using IIR Butterworth filter providing significant reduction in power spectral density levels between 50 to 60 Hz. The finally reconstructed ECG signal yields reasonably good impulse noise as well as powerline suppression using the proposed approach.

Denoising images corrupted by impulsive noise using projections onto the epigraph set of the total variation function (PES-TV)

Abstract: In this article, a novel algorithm for denoising images corrupted by impulsive noise is presented. Impulsive noise generates pixels whose gray level values are not consistent with the neighboring pixels. The proposed denoising algorithm is a two-step procedure. In the first step, image denoising is formulated as a convex optimization problem, whose constraints are defined as limitations on local variations between neighboring pixels. We use Projections onto the Epigraph Set of the TV function (PES-TV) to solve this problem. Unlike other approaches in the literature, the PES-TV method does not require any prior information about the noise variance. It is only capable of utilizing local relations among pixels and does not fully take advantage of correlations between spatially distant areas of an image with similar appearance. In the second step, a Wiener filtering approach is cascaded to the PES-TV-based method to take advantage of global correlations in an image. In this step, the image is first divided into blocks and those with similar content are jointly denoised using a 3D Wiener filter. The denoising performance of the proposed two-step method was compared against three state-of-the-art denoising methods under various impulsive noise models.