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Showing 2 results for Active Noise Control
H.r. Talesh Bahrami, H. Parhizkar, S. Ghasemlooy,
Volume 19, Issue 5 (5-2019)
Abstract
one of the key issues in the design of high-speed modern devices such as giant aircraft and high-speed trains. In this regard, it is to design these devices in such a way to have at least aerodynamic noise. The cylinder, as a bluff body, is widely used in the design of various devices, such as a landing gear. Therefore, the reduction of cylinder noise can be widely used. In the present study, numerical solution is used to present a method for reducing the noise generated by flow on the cylinder. This is done by flow suction from the grooves the cylinder. Acoustic numerical calculations were performed, using LightHill's acoustic analog approach in the form of wave equations of Ffowcs-Williams & Hawkings model. The numerical solution is performed in the three-dimensional unsteady form, using the large eddy simulation turbulence model. The characteristics of the grooves, such as their dimensions and distance the generated acoustic noise have been studied. The results show that the active control method presented in this paper is an effective and yet simple way to control noise. The cylinder used in the present study produces a noise of about 110 dB at a speed of 250 km/h. According to the results, it can be said that by optimally arranging the number of slots and creating a proper flow suction, its sound level can be reduced to about 60 dB.
Ehsan Tahvilian, Milad Iranpour, Ali Loghmani,
Volume 22, Issue 9 (9-2022)
Abstract
Low-cost and highly effective noise reduction has recently become one of the substantial challenges for industrial manufacturers. This paper presents the design and construction of a cost-effective system for attenuating single-frequency annoying noise generated from industrial products and machines. To achieve this goal, narrowband active noise control using Filtered-x Least Mean Square (FxLMS) method has been used with the help of a two-factor digital adaptive filter, called the adaptive notch filter. Therefore, a duct structure has been designed and experimental tests have been performed on it. To reduce implementation costs, the Arduino Uno board, which has an AVR microcontroller (ATmega328P), has been used as the controller. About 15dB noise attenuation at 400Hz and 750Hz frequencies and about 30dB noise attenuation at 650Hz and 950Hz frequencies have been achieved. Then, active noise control for two separate and simultaneous frequencies has been performed, which had somewhat effective results, and in one of these frequencies, noise attenuation of about 18dB has been observed.
