Showing papers on "Impulse noise published in 1991"

The HDSL environment (high bit rate digital subscriber line)

Abstract: The author presents a tutorial on the physical environment in which high bit rate digital subscriber line (HDSL) transceivers will have to evolve and succeed. Special attention is given to the most damaging impairments that are encountered in subscriber lines, such as propagation loss, linear distortion, crosstalk, bridged taps, and impulse noise. Somewhat less important impairments, such as change of gauge, temperature variation, and thermal noise, are also briefly described. The author concludes with a discussion of the capacity of a twisted-pair channel in a crosstalk-dominated environment. >

Impulse noise: Some definitions, physical acoustics and other considerations

Abstract: An overview of the impulse noise (blast wave) stimulus is presented with an emphasis on examining those parameters that have been traditionally used to quantify the stimulus for the purpose of understanding its effects on hearing.

Apparatus and method for reducing errors in data caused by noise

Abstract: In a power line communications apparatus an improvement for blanking or snubbing impulse noise. The impulse noise is detected and used to snub the detected signal. The duration of the snubbing pulses is controlled to assure complete blanking of noise including the trailing noise signals following a main noise pulse which may not otherwise be detectable. Also, the number of snubbing pulses which can occur are limited to prevent too much energy from being snubbed during any given baud period.

Delayed temporary threshold shift induced by impulse noises (weapon noises) in men.

Abstract: Most of the available information on the effects of impulse noise on hearing is derived from temporary threshold shift (TTS2) measurements performed 2 min after a single exposure to small-weapon noises. TTS is known to recover as a linear function of the logarithm of time when it is induced by a continuous noise of moderate intensity. Following the exposure to impulse noise, several investigators have reported individual exceptions to the log-time relation, e.g. increases in TTS during the first hour of recovery. These authors observed a ‘rebound recovery function’ for most of the exposed men, and they conclude that this phenomenon … has implications for the use of TTS in the construction of damage risk criteria for hazardous noise exposure …, a single measure, such as the widely used TTS2 may not be an adequate index of the magnitude of the TTS'. In order to thoroughly investigate in man the existence of ‘delayed’ TTS following the exposure to actual weapon noises, the ‘French Committee on Weapon Noises’...

Forward error correction for asymmetric digital subscriber lines (ADSL)

Abstract: The application of two types of forward error correction codes to the DS1 rate asymmetric digital subscriber line (ADSL) channel is examined: interleaved Reed-Solomon codes used for compact disc, and Iwadare burst error correction codes. A model is derived for the distribution of burst errors that impulse noise causes with ADSL. This model is used to analyze the performance of the codes in the presence of impulse noise. The bit error rate with crosstalk or Gaussian noise is also determined and results are compared to those for uncoded transmission. It is found that the compact disc codes are very effective for ADSL. >

Adaptive threshold suppression of impulse noise

Abstract: Impulse noise suppression upstream of digital processing circuitry contains a sample and hold mechanism which samples the input signal and stores a plurality of sequential sample values respectively representative of the amplitude of the input signal at successive sample times. The contents of the sample and hold mechanism are compared with an input signal sample to determine whether or not the there are abnormal amplitude variations which potentially constitute impulse noise. In one embodiment the comparison is referenced to the average magnitude of the input signal. In another embodiment the input signal is coupled to a cascaded arrangement of sample and hold circuits which sample and store a plurality of sequential sample values. The time differentials between successive sampling times are such there is little likelihood of occurrences of impulse noise spikes during any two successive sample intervals. The contents of the last sample and hold circuit of the cascaded plurality are compared with the contents of each of selected other sample and hold circuits of the cascaded chain. If the (earliest in time) sampled value stored in the last sampled and hold circuit is determined to be larger (by a system thermal noise offset) than the sampled value of any of the selected samples, then this sample is identified as being a potential noise impulse sample and is prevented from being coupled to downstream processing circuitry. Otherwise it is coupled through a downstream lowpass filter for subsequenty signal analysis.

Effects of peak pressure and energy of impulses.

Abstract: Peak pressure has been one of the key parameters of impulse noise used to assess the hazard to hearing. It is used in most international noise exposure limits. France uses an A‐weighted energy limit. There is a rough correspondence between peak pressure and the hazard to hearing for a given type of impulse noise. However, when the effects of different types of impulses are compared, this correspondence breaks down. One of the alternate measures of impulse intensity is weighted energy. Weighted energy is appealing for a number of reasons. It does not depend on details of the pressure‐time history such as the peak pressure and the more common duration measures. It should be easier to integrate with continuous or intermittent noise standards. It would make it easier to use standard hearing protector attenuation to estimate the hazard when a specific hearing protector is worn. Results of previously published articles and reports will be discussed. These reports lead to the conclusion that weighted energy is a more potent determiner of hearing hazard than peak pressure if spectral effects are controlled.

A comparison of passband and baseband transmission schemes for HDSL

Abstract: Using an ideal decision feedback equalizer (DFE), the SNR of quadrature amplitude modulation (QAM) and baseband pulse amplitude modulation (PAM) in the presence of self near-end crosstalk is computed for a large sample of loops within a carrier serving area (CSA). When baud-space feedforward filters are used, PAM has 1-2 dB more SNR than QAM, where the type of PAM is the 2B1Q line code. However, when using fractionally spaced feedforward equalizers (FSEs), the SNRs of 2B1Q and QAM are almost equal for loops at the extreme range of a CSA. Four- and 16-state trellis-coded modulation is applied to PAM and QAM. Coded and uncoded PAM and QAM are simulated with parallel decision feedback estimation. Viterbi receivers and coding gains are computed. QAM has up to 1 dB higher coding gains that PAM. However, the higher coding gains of QAM do not compensate for the lower SNR of uncoded QAM, and coded QAM has worse performance than coded PAM in the presence of self near-end crosstalk. The error rates of PAM and QAM with impulse noise are computed using a collection of measured impulse noise events. Results indicate that QAM has a lower error rate than PAM in the presence of impulse noise. >

New algorithms for adaptive median filters

Abstract: We present two robust adaptive median filters with variable window size which are capable of removing a mixture of positive and negative impulse noise while preserving sharpness of an edge In the first case, we assume that each pixel at (i J ) is corrupted by an impulse with probabilitype independent of other pixels corrupted or not The impulse corrupted pixel takes on the minimum pixel value smm with probability q or the maximum pixel value mwith probability 1 when the original pixel s is corrupted by a negative or a positive impulse, respectively Let {x } be the noise corrupted image Then I e,1 with Pe xii = 1 with 1 The RAMF algorithm is based on a test for the presence of an impulse at the center pixel followed by a test for the detection of residual impulse in the median filter output In the second model, the noise corrupted pixel is x =s +n1 , where n1 is iid impulsive noise having Laplacian, or Cauchy, or a mixture of Gaussian and Cauchy distributions The SAMF algorithm in this instance detects the width of the impulse and adjusts the window accordingly until the noise is eliminated These algorithms were tested on standard images The RAMF is shown to be supenor to the nonlinear mean L filter[1] while the SAMF is better performing and simpler than [in's adaptive scheme[3]

Neural networks for signal/image processing using the Princeton Engine multi-processor

Abstract: The authors describe a modular neural network system for the removal of impulse noise from the composite video signal of television receivers, and the use of the Princeton Engine multi-processor for real-time performance assessment. This system out-performs alternative methods, such as median filters and matched filters. The system uses only eight neurons, and can be economically implemented in VLSI. >

On impulse noise removal in color images

Abstract: The failure of well-developed techniques for grey-level scalar images when directly applied to remove impulse noise with median filters in color vector images is illustrated. Pertinent criteria to remove noise in color images with median filters and reconstruct the perceptually optimum output of the median filters are derived and justified. The experiments demonstrate noise suppression and minimization of color distortion. >

The Hazard of Exposure to Impulse Noise as a Function of Frequency. Volume 1

Abstract: : The energy spectrum of a noise is known to be an important variable in determining the effects of a traumatic exposure. However, existing criteria for exposure to impulse noise do not consider the frequency spectrum of an impulse as a variable in the evaluation of the hazards to the auditory system. This report presents the results of a study that was designed to determine the relative potential that impulsive energy concentrated at different frequencies has in causing auditory system trauma. One hundred and eighteen (118) chinchilla, divided into 20 groups with 5 to 7 animals per group, were used in these experiments. Pre- and post-exposure hearing thresholds were measured at 10 test frequencies between 0.125 and 8 kHz on each animal using avoidance conditioning procedures. Quantitative histology (cochleograms) was used to determine the extent and pattern of the sensory cell damage. The noise exposure stimuli consisted of six different computer-generated narrow band tone bursts having center frequencies located at 0.260, 0.775, 1.350, 2.450, and 3.550 kHz. Each narrow band exposure stimulus was presented at two to four different intensities. An analysis of the audiometric and histological data allowed frequency weighing functions to be derived.

Impulse noise generator--design and operation.

Abstract: In the seventies PFANDER (Pfander, 1975) proposed a screening test with an impulse noise simulator to check the particular responsivity of soldiers on vulnerability of the inner ear concerning the impulse noise-induced hearing loss. According to a system developed at the University of Oldenburg (Germany) (Klug & Radek, 1987), we have constructed an impulse noise generator designed for our specific requirements that will be presented. The simulator consists of an electrical ignited impulse noise spark gap which is supplied by a 3.5 kV high voltage source. At a distance of 1.10 m from the center of the impulse noise spark gap a peak pressure level of 155 dB with a C-Duration (Pfander, 1975) of .2 msec and with the main energy in the frequency range from 1 kHz to 2 kHz was good reproducible. It would be preferable to shift the impulse noise spectrum to lower frequencies but experimental effort has failed so far.

Error Control Codes For Advanced Television Signals Based Upon Preliminary And Post Filtering

Abstract: Several aspects of the design of filters for burst error control for television signals in new or existing, analog or digital formats wili be described. The error control capability is provided by prefiltering, so no redundant information need be transmitted. Prefilters which minimize distortion of the image and optimize effectiveness in estimating errors will be discussed. Postfilters which can compensate for the prefiltering, further minimizing the small distortion are discussed. These error control methods can implement very efficient real-number outer codes that provide burst or impulse noise protection for signals in digital format that may employ standard finite-field inner codes, data compression algorithms, and other digital or analog processing. This inner processing can exacerbate impulse noise or cause substantial burst errors, which should be removed by outer codes, such as the described ones, in order to achieve the desired subjective improvement of advanced television.

Preliminary experience with the impulse noise simulator to identify individuals particularly sensitive to sound.

Abstract: The impulse noise simulator test, in which an impulse noise in the frequency range of 1000-2000 Hz with a peak pressure below the limit of tolerance is produced, constitutes, according to our experience so far, a useful test to recognize the so-called vulnerable ear and to exempt the persons concerned from exposure to impulse noise during their military service or to monitor them audiometrically in connection with firing exercises. The investigations show that TTS after simulator test is higher than after regular shooting exercises with weapons with lower frequency spectrum. This is a remark that bands, produced by weapons with larger caliber are less dangerous for hearing than those with a higher spectrum like G-3 and the simulator.

The Hazard of Exposure to Impulse Noise as a Function of Frequency. Volume 2

Abstract: : The energy spectrum of a noise is known to be an important variable in determining the effects of a traumatic exposure. However, existing criteria for exposure to impulse noise do not consider the frequency spectrum of an impulse as a variable in the evaluation of the hazards to the auditory system. This report presents the results of a study that was designed to determine the relative potential that impulsive energy concentrated at different frequencies has in causing auditory systems trauma. One hundred and eighteen (118) chinchilla, divided into 20 groups with 5 to 7 animals per group, were used in these experiments. Pre- and post-exposure hearing thresholds were measured at 10 test frequencies between 0.125 and 8 kHz on each animal using avoidance conditioning procedures. Quantitative histology (cochleograms) was used to determine the extent and pattern of the sensory cell damage. The noise exposure stimuli consisted of six different computer-generated narrow band tone bursts having center frequencies located at 0.260, 0.775, 1.025, 1.350, 2.450, and 3. 550 kHz. Each narrow band exposure stimulus was presented at two to four different intensities. An analysis of the audiometric and histological data allowed a frequency weighting function to be derived. The weighting function clearly demonstrates that equivalent amounts of impulsive energy concentrated at different frequencies is not equally hazardous to auditory function. Comparison of this weighting function with the A-weighting function showed that A-weighting overestimates the hazard from low frequency impulsed. This volume contains individual threshold shifts and sensory cell loss data.

Digital high-frequency glitch noise eliminating method by current feed back

Abstract: The method is for removing the glitch noise generating at the high speed switching element by using an invert buffer gate element because it is the instantaneous impulse noise with low power. A glitch noise output tap (1) is connected to an input tap (2) and another input tap (6) through a pair of inverters and non- inverter buffer gates (30,3'), and an output tap (4). A current path (5) is connected between the output (4) and input (2) taps so that the glitch noise is sinked to the glitch noise output tap (1).

A model of impulse noise in digital subscriber loop

Abstract: A statistical model of impulse noise (IN) in digital subscriber loop is proposed. The IN is represented with one or several independent noise sources, which makes it possible to consider the burst nature and spectral properties of IN. The measurement scheme to estimate the IN model parameters, is presented. The model enables optimization of the receiver with regard to IN. >

Distribution of Amplitudes and Time Intervals between Partial Discharges

Abstract: Measurement of the impulse noise of partial discharges (PD) in previous paper1) has been carried out. To make a relation between obtained experimental results on discharge pulses and geometrical properties of cavities which cause partial discharges a statistical theory has been proposed.

Improved ultrasonic B-scans using deconvolution and morphological filters

Abstract: Resolution of ultrasonic B-scans for NDE is limited by the bandwidth of the transducer and the presence of noise. An improvement in signal-to-noise ratio (SNR) can be obtained, to some extent, by performing ensemble averaging of numerous measurements. This method is impractical and can not eliminate interfering echoes resulting from stationary scatterers. Contrary to averaging, morphological filters, a class of nonlinear filters, are capable of eliminating impulse noise, moderately reducing grain echoes and improving the overall image quality while selectively preserving certain image features. The authors have applied deconvolution and morphological filters in tandem (i.e., deconvolution before or after morphological operations) in order to improve resolution and SNR. In particular, the performance of these algorithms and the design of the deconvolution kernel and structuring element as well as morphological filters are evaluated using experimental results. >

Codes for Adva pon Preliminary

Abstract: burst error control for television signals in new or existing, analog or digital formats will be described. The error control capability is provided by prefiltering, so no redundant information need be transmitted. Prefilters which minimize distortion of the image and optimize effectiveness in estimating errors will be discussed. Postfilters which can compensate for the prefiltering, further minimizing the small distortion are discussed. These error control methods can implement very efficient real-number outer codes that provide burst or impulse noise protection for signals in digital format that may employ standard finite-field inner codes, data compression algorithms, and other digital or analog processing. This inner processing can exacerbate impulse noise or cause substantial burst errors, which should be removed by outer codes, such as the described ones, in order to achieve the desired subjective improvement of advanced television. Several aspects of the design of filters for

Satellite broadcast receiver

Abstract: PURPOSE:To attain sure noise reduction with simple constitution by applying noise reduction for only a period in the presence of an impulse noise signal. CONSTITUTION:The receiver is provided with an FM demodulation circuit 1, a video processing circuit 6, a band pass filter 11, an amplitude detection circuit 12, and a level detection circuit 13. A base band signal Sb by the substantial broadcast, a triangle noise signal Ss, and an impulse noise signal Si due to the deterioration in the C/N are included in an FM demodulation output, and in such a case, the signal Si is detected at a frequency band in which the level of the impulse noise signal Si is larger than the level of the triangle noise signal Ss to a discriminatable degree, and noise reduction or elimination processing is applied to a color composite video signal Sc by the detection output. Thus, the noise is surely reduced and a high definition picture is displayed.