Showing papers on "Salt-and-pepper noise published in 1976"

Maximum likelihood pitch estimation

Abstract: A method for estimating the pitch period of voiced speech sounds is developed based on a maximum likelihood (ML) formulation. It is capable of resolution finer than one sampling period and is shown to perform better in the presence of noise than the cepstrum method.

Noise filtering device

Abstract: Noise such as hum (whose components are self-correlated over a long time-interval) is estimated (separated) from Signal such as speech (whose components are self-correlated only over a short time-interval) by using a time-domain transversal filter, whose tap-weight coefficients may be fixed (Wiener filter) or variable (Adaptive filter). A combiner combines the estimated noise and original input signal to develop an output speech signal free of noise. The output speech may by further applied to a spectrum shaper to restore a natural shape.

ELF atmospheric noise excision by wideband clipping

Abstract: Because of the low transmitted power levels that are feasible in the extremely low frequency (ELF) band, it is essential to exploit such noise excision methods as are available to maximize communications signal-to-noise ratio (snr). A method that employs wideband clipping on ELF noise to match it to a linear matched filter has been evaluated with the use of noise data from northern latitude receiving sites. The analysis of month-long samples of noise data from all seasons and nearly all times of day indicates that an improvement in snr of at least 10 dB can be realized nearly all the time with the use of one or two parallel, manually adjusted clippers whose clipping levels are set on the basis of seasonal mean noise level.

Experiments in Digital Restoration of Defocused Grainy Photographs by Noise Cheating and Fourier Techniques

Abstract: An image enhancement technique called "Noise Cheating" allows the detection of low contrast objects in a noisy background. This technique has been applied to imagery degraded by blur and by noise. The technique is reviewed in this paper, and the results of its application are compared to the results using Wiener filtering. Comparisons are made on both computer simulated and laboratory-generated imagery. The results indicate that subjectively preferable restorations are achieved by Wiener filtering when blur, rather than image noise, is the dominant degrading factor, while noise cheating produces preferable results when noise is predominant.© (1976) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Wide‐hand noise reduction of noisy speech

Abstract: We present a new technique that reduces wide‐band noise in noisy speech. The concept of the approach is based on residual or voice excited linear predictive coding (LPC). The technique can be used in either a digital or an analog communication link that is degraded by quantization or receiver thermal noise, or both. The technique capitalizes on two effects. (1) Linear predictive coefficients representing an all‐pole vocal tract transfer function can be calculated unaffected by noise, if the noise present in speech is additive and white. (2) The signal‐to‐noise ratio of voiced sound in the fundamental frequency region of the voice band is much higher than that in the high‐frequency region. The basic procedure for conditioning noisy speech is as follows. When a voice signal that has been distorted because of quantization or thermal noise, or both, is received at a receiver, the decoded signal is analyzed to determine a set of LPC coefficients by the autocorrelation approach. The noise affects only the diago...