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Hearing, Sound, Noise, and Vibration
Published in R. S. Bridger, Introduction to Human Factors and Ergonomics, 2017
Office work usually involves conscious mental activities that fall prey to intrusion by noise. Several factors determine whether noise in offices will be a source of annoyance. First, if the noise level itself is too high, telephone or speech communication will be rendered more difficult and satisfaction with the environment reduced. If the noise level is too low (quiet enough to hear a pin drop), intermittent noises such as conversation, ringing telephones, loud traffic noise, etc., will be more likely to distract people. Sundstrom notes that the intensity of sudden noise above the background (the signal-to-noise ratio) is more important than the noise level itself in causing annoyance. White noise (noise in which amplitude is equal at all frequencies) is sometimes deliberately introduced into open plan offices to reduce the intensity of noise with respect to the background (to mask conversation, telephones, etc.).
Stochastic stabilization of rigid body motion of a spacecraft on SE(3)
Published in International Journal of Control, 2021
Naoya Tasaka, Satoshi Satoh, Takeshi Hatanaka, Katsuhiko Yamada
Regarding this point, this paper models the rigid body motion of a spacecraft under internal and external uncertainties as a stochastic system, whose kinematics is described by a stochastic differential equation (SDE) (Gihman & Skorohod, 1972; Ikeda & Watanabe, 1992; Oksendal, 1998). Then, we design a stabilizing controller and prove a stochastic stability theorem, where stochastic uncertainties are rigorously taken into account via stochastic calculus. Stability analysis using stochastic Lyapunov functions is a powerful scheme for a nonlinear stochastic system, since the analysis can be executed without using the solution process of the system, namely, a solution to a nonlinear SDE, which is analytically intractable in general. The stochastic controller can tackle a robust stabilization problem under stochastic disturbances driven by white noise. White noise itself contains all frequency components, and can generate other stochastic signals with specific frequency characteristics through appropriate shaping filters. Moreover, white noise is unbounded, and can be arbitrarily large at any finite interval. This makes stability analysis and controller design challenging.
Enhancing the quality of service of mobile video technology by increasing multimodal synergy
Published in Behaviour & Information Technology, 2018
F. van der Sluis, E. L. van den Broek, A. van Drunen, J. G. Beerends
The SNR was computed as follows: where the Root Mean Square (RMS) amplitudes of the signal and noise were, respectively, −15 and −6 dB and defined by where X is either the power of the noise or signal and Xr is the power of the reference point of the used dB scale. For all dB values, dB relative to full scale (dBFS) was used as unit of measurement for amplitude levels, with as reference point the digital system's maximum output level. As noise source, white noise was used: a random signal, which adds an equal amount of energy across all frequencies. The RMS for both the noise and signal were calculated and normalised using Syntrillium Software Corporation's Cool Edit Pro 2.1. Normalisation was realised by taking the signal's peak amplitude and amplify the entire signal with a scalar such that its RMS reaches the predetermined level, which is possible without clipping. Consequently, for all audio signals that have the same loudness level was secured.