Showing papers on "Impulse noise published in 1972"

Television receiver using synchronous video detection

Abstract: Synchronous video detection in a television receiver provides increased detection linearity and better signal-to-noise ratio for weak signals than does envelope video detection. Impulse noise, which produces generally unobtrusive black-going noise in a kinescope picture produced in accordance with a video signal recovered by envelope detection, conventionally produces obtrusive white-going noise as well in a picture produced in accordance with a video signal recovered by synchronous detection. Impulse noise detected by an auxiliary video detector responsive to the video i-f envelope provides a blanking signal to remove obtrusive white noise from the output signal of a synchronous video detector.

Growth and recovery of temporary threshold shift at 4 kHz due to a steady state noise and impulse noises.

Abstract: 7 audiometrically normal, male students were exposed to a steady state noise S of 98 dBA and 2 steady state-impulse combined noises A and B (steady state component of 97 dBA, hammer noise 102 dBA and air exhaustion noise of 118 or 110 dBA) for 40–60 min. The regression line of temporary threshold shift (TTS) growth due to noise A on exposure duration was significantly steeper than that due to noise B. Both the lines were steeper than that due to noise S. The reason of the relatively larger effects of the noises A and B as compared with noise S could be explained by the fact that the noise S did not contain impulse components, because the octave band level at center frequency of 3 kHz of the noise S was roughly equal to that of the steady state noise component of noise A or B. The relatively larger effect of the noise A than B might be attributed mainly to the air exhaustion noise. It was suggested that the effect of a steady state noise on hearing might be additive to that of an impulse noise. The trend relationship between TTS during recovery and recovery time was nearly the same with the 3 noises.

A study of FM threshold extension techniques

Abstract: The characteristics of three postdetection threshold extension techniques are evaluated with respect to the ability of such techniques to improve the performance of a phase lock loop demodulator. These techniques include impulse-noise elimination, signal correlation for the detection of impulse noise, and delta modulation signal processing. Experimental results from signal to noise ratio data and bit error rate data indicate that a 2- to 3-decibel threshold extension is readily achievable by using the various techniques. This threshold improvement is in addition to the threshold extension that is usually achieved through the use of a phase lock loop demodulator.

Understanding Impulse-Noise Measurements

Abstract: Numerous articles have been written on the general properties of impulse noise, models for it, and its effects on data transmission. Most of these make an attempt to apply or generate some particular theory with respect to the phenomenon. A literature search has given rise to an awareness of the need for a paper devoted solely to the idiosyncrasies of impulse-noise measurements and their interpretation. This paper first distinguishes impulse noise from background or message-circuit noise, then addresses itself to the time-variability problems associated with impulse noise. The use of electronic versus electromechanical impulse-noise counters is then discussed, followed by a presentation of practical measuring techniques, and finally by a few words on mitigative measures.

The Temporary and Permanent Threshold Shifts Produced by Three Levels of Impulse Noise

Abstract: Monaural chinchillas (15) were exposed to 50 impulses of either 155 or 161 or 166 dB peak SPL. The imuplses were generated by a shock tube and had an A duration of 1 msec. Quiet threshold was measured at 0.25, 0.5, 1, 2, 4, and 8 kHz using the average evoked response (AER) technique. Recovery was monitored for 31 days. The median PTS for all frequencies was determined by the level of the impulse: the 155 dB level produced essentially no PTS, the 161 dB level produced approximately 10 dB PTS across all frequencies, and the 166 dB level produced 13 to 35 dB PST. For moderate to severe TTS, as much as 14 h were .necessary to reach maximum TTS. Unlike PTS results, TTSmax was not strictly determined by the level of the impulse. Specifically, the correlation between the PTS and TTSmax ranged from only r = 0.34 to r = 0.75. The results will be discussed in reference to existing damage‐risk criteria for impulse noise. [Research supported by the Hendricks Foundation.]

A study of fm threshold extension techniques

Abstract: Investigations into the FM threshold phenomenon have resulted in the development of several signal processing techniques that can be implemented at the output of any FM demodulator, in- cluding phase lock loop and FM feedback demodulators, to provide improved system perform- ance. These techniques are based on the distinguishing characteristics of the demodulator output noise below threshold. Performance improvement and threshold extension are achieved by operating on the demodulator output signal and noise such that the threshold noise impulses are eliminated. The characteristics of three postdetection threshold extension techniques are evaluated with respect to the ability of such techniques to improve the performance of a phase lock loop de- modulator. These techniques include impulse-noise elimination, signal correlation for the detection of impulse noise, and delta modulation signal processing. Experimental results from signal-to-noise ratio data and bit error rate data indicate that a 2- to 3-decibel threshold extension