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Introduction
Published in Marek Pawelczyk, Stanislaw Wrona, Noise-Controlling Casings, 2023
Marek Pawelczyk, Stanislaw Wrona
Noise is currently one of the most significant hazards to humans in the workplace, making it difficult to communicate by voice, to hear alarms and warnings, and being the source of many ailments and diseases, especially hearing diseases. Noise at home makes it difficult to rest and causes irritation. Long-term exposure to noise at high sound pressure levels can lead to permanent hearing damage. These issues are the subject of many studies and are reflected in defined standards.
Motor Vibration and Acoustic Noise
Published in Wei Tong, Mechanical Design and Manufacturing of Electric Motors, 2022
Sound pressure is a measure of air pressure fluctuation a noise source creates. It is usually expressed in units of Pascal (Pa). However, the use of Pascal as the sound pressure unit may generate a broad range of sound pressures. A convenient way to compress the scale of numbers into a manageable range is to use decibel (dB). Sound pressure converted to the decibel scale is called sound pressure level (SPL), denoted as Lp: Lp=10log10(prms2pο2)=20log10(prmspο)
Sound Levels
Published in Fang Zhu, Baitun Yang, Power Transformer Design Practices, 2021
Sound pressure is a pressure fluctuation in the air which is caused by a sound source; it is this pressure fluctuation which our ear hears and which is measured by the microphone of a sound level meter. The measured value is related to distance from the source, frequency, background noise and sound reflection. Transformer “hum” is of low frequency, fundamentally 100 Hz for a 50 Hz unit or 120 Hz for a 60 Hz unit. The normal range of hearing for a healthy young person extends from approximately 20 Hz to 20 kHz. The definition of the sound pressure level is Lp=20×log10pp0
Design modification of three-blade horizontal-axis wind turbine for noise reduction
Published in International Journal of Ambient Energy, 2022
D. Rajesh, P. Anand, Nishant Kumar Nath
Wind turbines majorly produce noise due to the effect of mechanical parts and aerodynamic effects of wind on blades. Sound reduction became an important factor in maintaining wind farms. In sound propagation, there will be the formation of sound pressure levels around the wind turbine. Sound pressure levels are measured using sound level meters that consist of a microphone that converts pressure variations into a voltage time series output that is calibrated in decibels. Testing is done in the anechoic room to calibrate the sound levels as shown in Figure 4. The sound is sensed by the micro phone, which is directly connected to the sound level meter and the computing system (Manwell, McGowan, and Rogers 2009). Whenever the sound is generated by the wind turbine, due to pressure variations in atmosphere, the sound pressure will be calibrated by the CLIO software with the help of the electro-acoustic integrated system, and the values of the micrometre parameters are listed in Table 4.
The Effect of Interface Modifications Combination of Multiple Friction Blocks on Truck Brake Squeal
Published in Tribology Transactions, 2021
Y. K. Wu, C. Lu, J. B. Yin, Y. G. Micheale, Q. Wang, X. C. Wang
In recent years, some mechanisms have been proposed to explain the generation of brake squeal, which can be classified into the following categories: sprag–slip, stick–slip, hammering excitation, negative friction velocity slope, mode coupling, and splitting the doublet modes (21–30). With the proposed mechanism, the propensity and severity of the brake squeal can be predicted. Kang et al. (27) investigated the mode coupling type squeal mechanism of a disc brake system. Using eigenvalue analysis and the Rayleigh-Ritz method, the mode shapes of the disc and brake pad (an annular sector plate) can be obtained. Abubakar and Ouyang (28) established a contact interface model considering the friction material on a macroscopic scale. It was found that the reliability and predictability of the complex eigenvalue analysis (CEA) can be increased with the proposed model. Chen et al. (29) studied the effect of the braking pressure variation on railway vehicle brake squeal through experimental tests and finite element (FE) analysis. The results indicated that CEA can accurately predict the frequency of brake squeal. Hou et al. (30) investigated the tendency of brake squeal. It was found that when a damping layer was added, the noise and sound pressure level were greatly reduced.
The hearing health of live-music sound engineers
Published in Archives of Environmental & Occupational Health, 2021
Siobhan McGinnity, Elizabeth Francis Beach, Robert S. C. Cowan, Johannes Mulder
Worldwide, roughly 16% of adult-onset hearing loss is attributed to damage resulting from exposure to occupational noise, making it second only to presbycusis as the leading cause of deafness.4,5 For LMSE, the occupational hazard to their hearing arises directly from the music that they help to create, and thus the appropriate nomenclature is music-induced hearing injury (MIHI). This encompasses a cluster of symptoms and auditory damage profiles, resulting from exposure to excessive and/or prolonged sound pressure levels. In acute forms, MIHI occurs as very rapid destruction of the vulnerable inner-ear structures following exposure to sound levels above 130 dB. More common chronic forms, however, are acquired from cumulative injury due to exposure to moderate-to-high sound levels over a prolonged period or from multiple incidents.6,7 The reported auditory symptoms of hearing injury include hearing loss, tinnitus, distortion, diplacusis and hyperacusis. Kähäri et al. reported that 74% of 139 rock/jazz musicians surveyed experienced such symptoms.8