Physics
Noise Sensitivity
Noise sensitivity refers to the degree to which a system or device is affected by external disturbances or fluctuations, known as "noise." In physics, it is a measure of how susceptible a system is to random variations in its environment, and is often quantified in terms of signal-to-noise ratio. Understanding and managing noise sensitivity is crucial in fields such as electronics, telecommunications, and signal processing.
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4 Key excerpts on "Noise Sensitivity"
eBook - PDF- Karl D. Kryter, Douglas H.K. Lee, E. Wendell Hewson, C. Fred Gurnham(Authors)
- 2013(Publication Date)
- Academic Press(Publisher)
PART I AUDITORY SYSTEM RESPONSES TO NOISE Introduction In the fields of electronics, neurophysiology, and communication theory, noise means signals that bear no information and whose intensities usually vary randomly in time. The word noise is used in this sense in acoustics, but more often it is used to mean sound that is unwanted by the listener, presumably because it is unpleasant or bothersome, it interferes with the perception of wanted sound, or it is physiologically harmful. Noise, as unwanted sound, does not necessarily have any particular physical characteristic (such as randomness) to distinguish it from wanted sound. For example, an information-bearing signal such as speech may be so intense that it is subjectively unwanted and may even be harmful to the ear of the listener, whereas a sound such as so-called white noise that is random, or nearly so, in the physical sense may be subjectively quite acceptable, particularly if it serves to mask other sounds that, if audible, would be bothersome. As far as man's auditory system is concerned, there is no distinction to be made between sound and so-called noise, and in the text to follow the word noise is often used in place of sound merely to draw attention to the theme of the book. There are certain unwanted effects of sounds that appear to be related rather precisely to physical characteristics of the sound in ways that are more or less universal and invariant for all people. The effects we refer to are (a) the masking of wanted sounds, particularly speech, (b) auditory fatigue and damage to hearing, (c) excessive loudness, (d) some general quality of bothersomeness or noisiness, and (e) startle. These unwanted effects of sound upon man's peripheral and subjective auditory response system are mainly what this book is about.
eBook - ePubPhotoconductivity
Art: Science & Technology
- N V Joshi(Author)
- 2017(Publication Date)
- Routledge(Publisher)
5 Noise 5.1. SIGNIFICANCE OF THE TERM “NOISE”Noise in the present context is random and unpredictable fluctuations in voltage or in current. This is an unwanted property in any measurement system and normally determines its lower limit. Sometimes the magnitude of random fluctuations is higher than the signal to be handled, and in the case of device applications based on photodetector technology, this leads to incorrect information. If the fluctuations are of the same order as the signal, then, the signal is masked out and/or the desired information is perturbed. The noise consideration is of fundamental importance, particularly when the photoconductivity signal is very weak. An experimental physicist knows that after eliminating the random voltages originating from an improper experimental setup, there is always still noise that determines the measurement capability. In semiconductors, there are several reasons for random fluctuations in voltages.There are excellent textbooks and review articles [1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 ] on noise, and I do not intend to discuss all the aspects of noise and the methods of reducing its effects. We will focus our attention to those types of noise that are very specific to photoconductors and radiation-detecting devices.Noise in photodetectors degrades the signal, distorts the system performance, and limits the system’s capability. Understanding the origin of noise, its magnitude, frequency spectrum, and characteristics and its interrelation with other types of noise is a crucial aspect not only for the design of the photosensor but also for the experimentalist who works in radiation detection, particularly at low levels. The literature shows that noise analysis has helped to improve detector performance by aiding in the selection of a proper chopping frequency, an optimum bias voltage, adequate circuits or filters, and so on. The purpose of this chapter, therefore, is to introduce the types of noise that are frequently observed in photodetectors (both photoconducting and photovoltaic) and to describe them. This chapter will help to explain the importance of noise analysis in improving the limit of detectivity in visible and infrared photodetectors.
eBook - ePub- Shailaja Mahamuni, Deepti Sidhaye, Sulabha Kulkarni(Authors)
- 2020(Publication Date)
- CRC Press(Publisher)
2Improving Signal-to-Noise Ratio
2.1 Introduction
Noise, simply put, is any unwanted signal that interferes with the detection of the desired signal. For example, while listening to a specific sound, other background sounds (such as people talking, traffic, environmental sounds etc.) act as distractors and therefore can be considered as acoustic noise. Someone walking in front of you while you are watching TV can be considered as visual noise. The crackling sound that you may hear while listening to radio is caused by system noise. In this chapter, we will focus on the system noise, particularly that in an electrical system.In today’s experiments, a physical quantity is converted into an electrical signal, and is quantitatively measured in terms of either the electrical current or the voltage. These measurements are not free of noise-induced errors. The measured value of a quantity 5 can be represented ass = x + δ x(2.1)where x is the actual value of the quantity and δx is the measurement error. When every measurement is consistently smaller or larger than the actual value, it is considered as a ‘systematic error’ or an ‘offset’. Noise-induced errors, however, tend to be random or unpredictable. For reliable and accurate estimation of the actual value, it is necessary to minimise the influence of random, noise-induced errors in the measured value. A simple and the most common way to reduce the contribution of random noise is to average multiple measurements of the same quantity. The underlying assumption is that the actual value of the quantity remains constant across measurements, while the random noise is averaged out. Thus, the empirical estimation of the actual value obtained from N
eBook - PDF- Marco Tartagni(Author)
- 2022(Publication Date)
- Cambridge University Press(Publisher)
Part II Noise and Electronic Interfaces 6 The Origin of Noise Understanding the origin of the noise is essential, as it gives hints on how to reduce its effects even from the electronic point of view. This chapter will shortly analyze the physics background of some sources of random processes that are limiting sensing systems referred to as “thermal,” “shot,” and “flicker” noises. It will also show how thermal and shot noises are at the base of other observed electronic effects such as “kTC,” “phase,” and “current” noises. The discussion will use analogies between mechanical and electronic effects of thermal agitation. This is important not only for understanding the process but also to unify the noise model in microelectromechanical sensors systems to use the same analytical framework. 6.1 Thermal Noise Thermal noise is the most common source of noise found in electronics, and it will be introduced starting from some aspects of thermal agitation in classical statistical mech- anics. This is because noise is a random process resulting from the sum of a huge number of single contributions that could be modeled only from a statistical perspective. 6.1.1 A Simplified Mechanical Model A pressure sensor is illustrated in Fig. 6.1, where a gas whose pressure has to be measured is enclosed in a container by a lid/piston having 1 degree of freedom. The piston is kept in mechanical equilibrium by a spring. The increase of the gas’ s pressure moves the piston along the degree of freedom with respect to the initial equilibrium point so that its displacement gives the output of the system. The gas is composed of identical N single particles colliding with each other and against the container ’ s borders by elastic impacts. Instead of using the macroscopic definition of “pressure,” we will describe that as the average effect of the force exerted by collisions of particles with the piston, assuming the entire system is in thermal equilibrium.
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