China
Africa
Explore chapters and articles related to this topic
Sources of sound
Published in John Watkinson, The Art of Sound Reproduction, 2012
The timbre of the guitar is determined by the vibration of the structure and by the harmonic structure of the string vibration. If the guitar is played with a plectrum, the string will be bent to a sharper angle before it is released and this creates more high harmonics than fingering which bends the string to a radius.
Spectral Density
Published in David C. Swanson, ®, 2011
There are some simplified structural elements often referred to in textbooks which tend to have one dominant type of wave. For example, “rod” vibration refers to a long stiff element with compression waves propagating end-to-end like in the valves of a standard internal combustion engine. “String” vibration refers to mass–tension transverse vibration such as the strings of a guitar or the cables of a suspension bridge. “Shaft” vibration refers to torsion twisting of a drive shaft connecting gears, motors, and so on. Rod, string, and shaft vibrations all have a second-order wave equation much like the acoustic wave equation where the wave speed is constant for all frequencies and the solution is in the form of sines and cosines. “Beam” vibration refers to a long element with transverse bending shear vibrations such as a cantilever. “Plate” vibration refers to bending vibrations in two dimensions. Beams and plates have both shear and moment forces requiring a fourth-order wave equation, giving a wave speed which increases with increasing frequency, and a solution in the form of sines, cosines, and hyperbolic sines and hyperbolic cosines. “Shell” vibration is even more complex where the bending s-waves are coupled with compression p-waves. But here is a valuable secret about acoustics in general: it is almost impossible in nature to excite or isolate one type of wave. All types of waves are generated at the source and wave energy couples together between wave types at every discontinuity in impedance along the propagation path. One has to always be aware of wave mixture and coupling. It creates remarkably complicated fields, which is why measurement of parameters such as intensity is so useful.
Measurement of vibration in polyester filament yarns to detect their apparent properties
Published in The Journal of The Textile Institute, 2021
Mina Emadi, Pedram Payvandy, Mohammad Ali Tavanaie, Mohammad Mahdi Jalili
A set of components were used to construct a laboratory system for measuring the vibration of the strings. The components were equipped with a Sony RX10 high-speed camera. It had a 1.0-type (13.2 mm × 8.8 mm) Exmore® RS CMOS sensor with 960 frames per second. The end of a 30-cm string was fixed in the upper holder, and the other end was attached to a weight and released to form an initial tension in the string. Then, the bottom holder was fixed on the string to maintain this initial tension. The initial stimulation of the string was accomplished by a displacement in the middle of it. According to Figure 3, this stimulation occurred as the string was placed at the back of the needle and released at the zero moment. The high-speed camera recorded the string vibration, which was then processed as a video file (Emadi, Payvandy et al., 2020). The vibration test of the filament yarns was performed at the stimulation distances of 1.5 mm and 3 mm and with 20 and 50 cN weights to create tension in the yarns.
A superposition method of reflected wave for moving string vibration with nonclassical boundary
Published in Journal of the Chinese Institute of Engineers, 2019
Enwei Chen, Yuanqi He, Kai Zhang, Haozheng Wei, Yimin Lu
A traveling string model with fixed and spring-dashpot boundary condition is built and the motion equation is obtained by using the Hamilton principle. The reflection equations for fixed and spring-dashpot boundary conditions are given analytically. A novel superposition method for reflected waves is proposed to obtain the analytical solutions for the free vibration of an axially translating string. From application of this method, one can consider and examine the physical nature of the string vibration based on the concept of wave propagation.
Instantaneous identification of tension in bridge cables using synchrosqueezing wave-packet transform of acceleration responses
Published in Structure and Infrastructure Engineering, 2022
Xin Zhang, Ye Lu, Maosen Cao, Shuai Li, Dragoslav Sumarac, Zeyu Wang
Generally, cable tension identification techniques fall into five categories, including lift-off technique (Ren, Chen, & Hu, 2005), optical fibre Bragg grating method (Li, Ou, & Zhou, 2009; Li, Li, & Song, 2004; Zheng et al., 2018), elastic-magneto method (Wang, Wang, & Zhao, 2005), elasto-magnetic-electric method (Duan et al., 2016), and vibration frequency-based method. Among the methods mentioned above, increasing interest has been paid to the vibration frequency-based method in monitoring cable tension due to the advantage of explicit mechanical foundation, facilitation in acquiring dynamic response, and low requirement for sensing fashion (Fang & Wang, 2012; He, Meng, & Ren, 2021; Liao, Ni, & Zheng, 2012; Ma, 2017; Nam & Nghia, 2011; Russell & Lardner, 1998; Triantafyllou & Grinfogel, 1986; Zhang, Peng, Cao, Damjanović, & Ostachowicz, 2020; Zui, Shinke, & Namita, 1996). The essence of this method is based on vibration theory that represents the relationship between vibration frequency and tension. In practical applications, the taut string vibration theory is used to calculate cable tension: where and are mass per unit length, taut tension, length, the nth frequency, and frequency order of the cable, respectively. In Eq. (1), and are constant parameters for specific cables. Thus, cable tension can be explicitly represented as a function with respect to and