China
Africa
Explore chapters and articles related to this topic
Spatial sound monitoring
Published in Francis Rumsey, Spatial Audio, 2012
Measurement methods using time-delay spectrometry or maximum length sequence signal analysis (MLSSA) techniques enable one to look at the impulse response of the direct signal and the room separately, and one can ‘window’ the impulse to observe different time periods after the direct sound. A window that includes the direct arrival and a portion of the reflected sound will give an indication of the effects of early reflection interaction at the listening position. Such an impulse response can be transformed into the frequency domain using an FFT (fast Fourier transform) to view the result as a frequency spectrum. Various time windows can be superimposed upon each other to create a so-called ‘waterfall plot’ that enables one to see the changing spectrum of the signal over time. This is useful for identifying the source of any particularly prominent reflections, and the effect on the resulting frequency spectrum (see Figure 5.9).
Three-objective optimization of aircraft secondary power system rotor dynamics
Published in Mechanics Based Design of Structures and Machines, 2022
Joseph Shibu K., K. Shankar, Ch. Kanna Babu, Girish K. Degaonkar
The three-dimensional (3D) plot of the vibration amplitude, rotor speed, and time is commonly referred to as waterfall plot. Waterfall plot of the engine run has clearly shown that the dominant vibration is the synchronous vibration and vibration at other frequency components is very small. Rotor response plot is superimposed to waterfall to identify the rotor speed corresponding to peak response. Further, color plots are generated by projecting 3D waterfall plot on to two-dimensional (2D) plot with color intensity to identify the vibration amplitude. In the color plot, X and Y axes represent frequency in Hz and time in seconds. The color bar shows the “g” value of vibration. In waterfall diagram, X, Y, and Z axes represent frequency in Hz, vibration response in “g” value, and time in second, respectively. Maximum “g” load of 13.83 g corresponds to a frequency of 406 Hz. The g load is transformed to response and is given in Table 4.