Noise pulses

For the amplifier pulse to be recognized in the ADC, it must exceed the lower level set by a discriminator, which is used to prevent noise pulses from jamming the converter. Once the pulse is accepted it is used to charge a capacitor that is discharged through a constant current source attached to an address clock typically... 

Fig. 14. Esxtracting distinguishing features from noise pulse signal. Wavelet coefficients in shaded regions represent stable extrema, (a) Wavelet decomposition of noisy pulse signal (b) wavelet decomposition of pulse signal. (Reprinted from Bakshi and Stephanopoulos, Representation of process trends. Part III. Computers and Chemical Engineering, 18(4), p. 267, Copyright (1994), with kind permission from Elsevier Science Ltd., The Boulevard, Langford Lane, Kidlington 0X5 1GB, UK.)...

It is even possible for an individual noise pulse to exceed — ET so that a negative reading of Ex will be obtained. This happens in the real world and therefore must be taken into account in the mathematical description. This is a good place to also note that since the transmittance of a physical sample must be between zero and unity, Es must be no greater than If, and therefore when If is small an individual reading of Es can also be negative. Therefore it is entirely possible for an individual computed value of T to be negative. 

We left off in our previous Chapter 44 with having concluded that the noise level becomes infinite, both for individual noise pulses, and for the variance of the noise, when value of the reference signal actually crosses zero and becomes negative we learned this from the following equation, which we reproduce from our previous chapter ... 

Liquid scintillation counters are highly efficient for low CL intensities and consist of two photon-counting channels provided with a variable discriminator. The sample is placed between these two detectors to ensure a high optical efficiency. The discriminator is adjusted to allow photon impacts to be transmitted and small background noise pulses to be rejected. As disadvantages they suffer from saturation errors and provide nonlinear relationships between the CL intensity and the total counts. 

A single channel pulse height analyser utilizes an electronic gate typically 0.1 V wide, which only accepts pulses between the preset upper and lower limits. Scintillation counters frequently employ such devices to remove small noise pulses and large pulses initiated by cosmic rays, as well... 

The electronic instrumentation necessary for the operation of the proportional counter is shown in Figure 18.6. Pulses from the detector pass through a preamplifier and amplifier, where they are shaped and amplified. Emerging from the amplifier, the pulses go to a discriminator. The discriminator is set so as not to trip on noise pulses but rather to trip on radiation pulses of any larger size. The number of discriminator pulses produced is recorded by the scaler. 

It should be noted that the problem of transient noise pulses can in principle be circumvented by use of suitable playback technology. For example, in the case of gramophone disks the use of a laser-based reader should eliminate any mechanical resonance effects and thus reduce the artifact to a large click which can be restored using the methods of previous sections. Of course, this does not help in the many cases where the original source medium has been discarded after transcription using standard equipment to another medium such as magnetic tape ... 

Model-based separation methods. A full study of the noise pulse mechanism would involve physical modelling of the (possibly non-linear) playback system for both gramophone systems and optical sound track readers. A full description is beyond the scope of this article (see [Roys, 1978] for some more detail), but can be used to shed... 

Noise pulse from optical film sound track ( silent section) 157... 

A further problem which is common to several recording media including gramophone discs and optical film sound tracks is that of low frequency noise pulses. This form of degradation is typically associated with large scratches or even breakages in the... 

A linear modelling approach to noise pulse removal is presented in [Godsill, 1993], In this it is assumed that the corrupted waveform x consists of a linear sum of the underlying audio waveform s and resonant noise pulses v ... 

Terms of this equation are defined similarly to those for the LSAR interpolator of section 4.3.3, with subscript V referring to the autoregressive process for the noise pulses. Av is a diagonal matrix whose mth diagonal element Xy m is the variance of the with noise excitation component, i.e. 

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