Showing papers on "Impulse noise published in 1978"

Impulse noise limiter circuit

Abstract: An impulse noise limiter circuit comprises a delay circuit for delaying a signal containing impulse noise and a clamp circuit provided between the input and output terminals of the delay circuit for limiting the voltage difference between the terminals to a given value.

Reduction of impulse noise contribution to receiver squelch threshold

Abstract: A receiver includes demodulator, squelch gating and squelch circuit for controlling the gating. A blanking circuit, responsive to impulse type noise, prevents impulse noise energy from contributing to the control of the gating.

On Optimum Receivers for Analog Communication in Impulsive Noise

Abstract: In this paper the problem of impulsive noise suppression in analog communication systems is considered. The problem of demodulation of amplitude and phase modulated signals in the presence of impulsive noise is formulated by introducing a binary random process to indicate the presence of impulsive noise. It is shown that sub-optimal receiver structures can be derived using this model and these are similar to some experimental receivers reported earlier in the literature. The receivers derived are non-linear in nature and their working is demonstrated through digital computer simulations.

Noise detector employing plural delay circuits

Abstract: An impulse noise detector, for use in impulse noise suppressor circuits which are used for suppressing scratch noises in disc record players, comprises a rectifier operable on an applied signal to provide a rectified signal, a smoothing circuit for smoothing the rectified signal, a pair of delay and invert circuits operable on the smoothed signal for affording a corresponding plurality of time delayed signals, and a combiner for selectively combining the time delayed signals to afford an output which is indicative of the presence, in the applied signal, of impulse noise.

The Speech Enhancement Advanced Development Model.

Abstract: : This report describes the design, principles of operation, and performance characteristics of an Advanced Development Model of a speech enhancement unit. This unit improves the quality and intelligibility of speech signals by the removal of frequently encountered interference or noise from received or recorded speech signals. A high speed digital array processor and various time and frequency domain algorithms permits the detection and attenuation of narrowband noise (such as tones, hums, whistles, etc.) and impulse noise (such as ignition pulses, static, etc.) with minimum degradation to the speech signals. The enhancement unit provides automatic tracking and attenuation of interferring signals in real time and with a maximum lag of .15 second. The heart of the speech enhancement unit is a powerful computer known as a macro-array processor, or MAP, that performs all of the measurement, analysis, and processing of the input signal. It is supported by a digital magnetic tape unit used to program the MAP and a minicomputer which reads the program into the MAP. Tests on the unit showed attenuation of 30 to 50 db on both narrowband and impulse noise. Operational tests performed by trained Air Force personnel showed the unit to be highly effective in providing improved intelligibility and listenability which significantly reduced listener fatigue. Provision has been made in the design and fabrication of the speech enhancement unit to implement a technique for attenuating wideband random noise. This technique known as INTEL is one of the few known methods of suppressing this commonly encountered noise without severely distorting co-existing speech.

Growth function for human response to large‐amplitude impulse noise

Abstract: The U. S. Environmental Protection Agency has proposed the use of C‐weighted day/night level for the assessment of impulse noise such as the noise resulting from sonic boom, blast noise (artillery, armor, demolition, etc.) and other large‐amplitude impulse sources. One remaining question pertaining to the use of C‐weighting has been the growth function for human response to impulse noise. This question arises because work by Kryter and by Young using peak values and/or small amplitudes exhibited growth functions of 6−7dB for a doubling of annoyance, while the growth function for human response to common sources (planes, vehicles, etc.) increases by about 10 dB for a doubling of annoyance. Kyter’s and Young’s data are reanalyzed herein by using C‐weighting and by including only large‐amplitude data. This reanalysis results in a growth function for human response to impulse noise which increases by about 10 dB for a doubling of annoyance. This equality of growth function between common A‐weighted noise and ...

Noise cancellation circuit

Abstract: A noise cancellation circuit is provided for cancelling impulse noise in a composite video signal. A composite video signal which may be contaminated with impulse noise is coupled to a noise inverter and an active filter. The noise inverter generates an inverted noise pulse for each noise pulse in the composite video signal which exceeds a predetermined threshold level. The active filter delays the composite video signal and combines the delayed video signal with the inverted noise pulses, resulting in cancellation of the impulse noise. The noise-free video signal is amplified by the active filter for subsequent signal processing. The threshold level of the noise inverter varies in response to the signal level at the output of the active filter. The active filter utilizes a feedback capacitor to delay the video signal and to improve the transition time of the leading edges of synchronizing signal components of the video signal. The feedback capacitor may be constructed from N+P+ semiconductor material, which is especially advantageous in integrated circuit manufacture.