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Organization Safety Procedures
Published in Dhananjoy Ghosh, Safety in Petroleum Industries, 2021
It is a general experience that working at a high noise level causes not only auditory effects in human beings, but also may result in cardiovascular attacks, gastro-intestinal disorders and psychological disorders. In view of this, a noise exposure limit has been set in the industry at 90 dB (decibel) with exposure for 8 hours; higher levels like 95 dB are allowed for exposure up to 4 hours, 110 dB up to 1 hour and momentary peak allowed up to 140 dB. Hence, the vendors while supplying the equipment to the industry take care of this issue during design.
Heat flux measurements: theory and applications
Published in Kaveh Azar, in Electronic Cooling, 2020
These estimates of time constants and frequency response characteristics can be important to the proper design of the experiment. For example, if a very fast (i.e., a small diameter) thermocouple is used in an experiment such as that by Azar and Moffat (1991), it will respond to vortices and turbulence in the flow. A fast data acquisition system would be able to resolve the lower frequency (larger scale) turbulent fluctuations. The effect will appear to be noise on the sampled data; this is a case where faster is not necessarily better. If the data on these measurement fluctuations are not needed in the experiment, the first-order response characteristics of the thermocouple can be used as an effective analog filter. The heat transfer characteristics of the thermocouple can be changed to increase time constant and lower the break frequency. For frequencies above the break frequency, the thermocouple acts as a low-pass filter with a rolloff (attenuation) of 6 db/octave. The definition of a decibel is db = 10 log10 (A2/Al). Based on this, the measured amplitude of any fluctuations in the gas temperature will decrease by a factor of four every time the fluctuation frequency doubles. This is a different approach for using heat transfer to enhance measurements.
Force-System Resultants and Equilibrium
Published in Richard C. Dorf, The Engineering Handbook, 2018
Note in Figure 102.5 that both decibel magnitude and angle are plotted semilogarithmically. The frequency axis is logarithmically scaled so that every tenfold, or decade, change in frequency occurs over an equal distance. The magnitude axis is given in decibels. Positive decibel magnitudes correspond to amplifications between input and output that are greater than one (output amplitude larger than input). Negative decibel gains correspond to attenuation between input and output (output amplitude smaller than input). Notice in Figure 102.5 that at low and high frequencies the straight-line approximations are virtually identical to the exact curves. The straight-line approximations differ most greatly from the exact curves at points where the approximations change slope. In magnitude curves these are called breakpoints. At breakpoints the straight-line approximation and the exact curve differ by 3 dB for each pole or zero.
Dispenser-printed sound-emitting fabrics for applications in the creative fashion and smart architecture industry
Published in The Journal of The Textile Institute, 2019
Yi Li, Russel Torah, Yang Wei, Neil Grabham, John Tudor
The audio source emits all frequencies in the audible range from 20 Hz to 20 kHz in the sine sweep mode over a 20 s time span. The audio source output level is −3 dBFS. The unit of dBFS is equivalent to the decibel level relative to the full scale sine wave showing the maximum peak value. Sine sweeps are used as reference tones to observe the frequency response or identify the adverse effects of room modes; for example, the room background noise is typically in the range of 20 to 200 Hz. The sine sweep produces frequencies with a much higher energy compared to pink noise or white noise. A sine sweep produces only one frequency at a time unlike pink or white noise which produces many frequencies simultaneously. The advantage of the sine sweeps is that it ignores the ambient noise in the room offering better immunity for measuring the frequency response at each fixed frequency value.
An Adaptive Denoising Algorithm for Online Condition Monitoring of High-Voltage Power Equipment
Published in Electric Power Components and Systems, 2020
Amjad Hussain, Zeeshan Ahmed, Muhammad Shafiq, Ashraf Zaher, Zeeshan Rashid, Matti Lehtonen
The decibel (dB) is a unit of measurement used to express the ratio of one value of a property to another on a logarithmic scale for measurements such as voltage, power, sound etc. It can also be used to express a change in a value such as in Eq. (5).
Hybrid analytical-numerical modelling of ground vibrations from moving loads in a tunnel embedded in the saturated soil
Published in European Journal of Environmental and Civil Engineering, 2022
Zonghao Yuan, Danting Xu, Li Shi, Xiaodong Pan, Ben He, Minyun Hu, Yuanqiang Cai
Floating slab track is widely used as effective means for vibration isolation in underground tunnels. In order to investigate the effect of the track system on the ground deformation, the radial displacement ur of the saturated soil at r = 6 m, θ = 0 and z = 0 for the cases with continuous floating-slab track and without track structure is presented in Figure 5. It is observed in Figure 5(a) the maximum displacement due to a constant moving load for the two cases appears at c/Vs = 1.0 (critical velocity of the tunnel-soil system, μ = 2 × 107 N/m2). The installation of floating slab tracks does not alter the critical velocity of the system. Generally, the soil displacement for the case with track is smaller than that without the track due to the fact that mounting a floating slab track on the tunnel invert allows the energy to propagate along the track before being transmitted into the tunnel and the soil. From Figures 3 and 5(a), the velocity effect is not important to modelling moving loads on track-tunnel-soil system. This is true up to c= 0.5Vs, which is higher than typical underground moving train velocity. Figure 5(b) compares maximum displacement amplitude in the free field due to a unit harmonic moving load (f0 = 1–200 Hz, c = 40 km/h) for the two cases. The response magnitude is presented in decibels ([dB] = 20log(P1/P2) in which P1 is the computed response amplitude, and P2 is the reference value with a unit value selected in this work). The displacement curve for the case without track shows an undulating characteristic due to the dynamic tunnel-soil interaction. For the case with track, a resonance peak can be observed at f0 = 19.02 Hz, which is the natural frequency of the slab calculated from a single degree system ( = 19.02 Hz). The isolation effect above f0 = 25 Hz is observed from Figure 5(b). The concept of insertion gain is usually used to evaluate the vibration isolation performance of the track. It is defined as the ratio of the soil response with track and soil response without track: