Active Reduction of Noise by Additional Noise Source and Its Limit

1989 ◽  
Vol 111 (4) ◽  
pp. 480-485 ◽  
Author(s):  
Ken’iti Kido ◽  
Hiroshi Kanai ◽  
Masato Abe
Keyword(s):  
Sound Source ◽  
Sound Pressure ◽  
Noise Control ◽  
Noise Source ◽  
Radiation Power ◽  
Active Noise Control ◽  
Primary Source ◽  
Dipole Source ◽  
Sound Sources ◽  
Effective Radiation

This paper describes further investigations of an active noise control system in which an additional sound source is set close to the primary (noise) source. Successful application of this method to duct noise control has already been reported (Kido, 1987). The synthesized sound radiated by the additional source is identical to that of the primary source, except in polarity. The additional and primary sources form a dipole sound source with reduced effective radiation power. In theory, the distance between these two sound sources should be much less than the shortest wavelength in the required frequency range to realize an ideal dipole source. Then, the total sound pressure would be expected to attenuate in proportion to the square of the distance from the center of the sources, and little sound power would be radiated. However, in practice, the distance cannot be set small enough, so there is only a relatively small area around the dipole where the sound pressure attenuates in proportion to the square of the distance. Further afield, it attenuates in direct proportion to distance. Noise reduction is therefore limited. This paper describes the effects and the limits of performance of such a system as a function of wavelength and the dimensions of sound sources.

NOISE SHIELDING BY SIMPLE BARRIERS: COMPARISON BETWEEN THE PERFORMANCE OF SPHERICAL AND LINE SOUND SOURCES

2000 ◽  
Vol 08 (03) ◽  
pp. 495-502 ◽  
Author(s):  
D. OUIS
Keyword(s):  
Sound Source ◽  
Insertion Loss ◽  
Line Source ◽  
Wave Reflection ◽  
Noise Source ◽  
Sound Level ◽  
Sound Sources ◽  
Noise Shielding ◽  
Noise Barrier ◽  
Wave Incidence

This study is concerned with the theoretical solution to the problem of sound screening by simple hard barriers on the ground with special emphasis given to the type of wave incidence, namely a comparison between the use of either a spherical or a cylindrical sound source. For a receiver at the shadow of the noise source, the field may be assumed to be due to the edge wave and for this, exact solutions are used. Regarding the wave reflection on an impedance ground, exact formulations are also used, and finally, some calculations are made on the performance of a hard noise barrier on a two-impedance ground. As a conclusion, it is found that although the sound level at the receiver may show some small differences depending on the frequency and on the geometry of the problem, the overall insertion loss of the thin hard barrier is almost the same for the spherical and the line source, and the differences are found to amount to less than 1 dB for geometries of practical occurrence.

Drivetrain Noise Source Identification and Active Noise Control of a Heavy Off-Road Vehicle

2019 ◽  
Author(s):  
Hailin Ruan ◽  
Wei Huang ◽  
Longchen Li ◽  
Zuguo Xia ◽  
Xiaojun Chen ◽  
...  
Keyword(s):  
Source Identification ◽  
Noise Control ◽  
Noise Source ◽  
Active Noise Control ◽  
Road Vehicle ◽  
Active Noise ◽  
Noise Source Identification

903 Active Noise Control Incorporating the Estimated Location of Noise Source

2014 ◽  
Vol 2014.67 (0) ◽  
pp. _903-1_-_903-2_
Author(s):  
Touma ITOU ◽  
Yosuke KOBA ◽  
Satoshi ISHIKAWA ◽  
Shinya KIJIMOTO
Keyword(s):  
Noise Control ◽  
Noise Source ◽  
Active Noise Control ◽  
Active Noise

scholarly journals Experimental Design Methodology for Global Active Noise Control in Enclosed Space

2021 ◽  
Author(s):  
Ikchae Jeong ◽  
Youngjin Park
Keyword(s):  
Experimental Design ◽  
Field Condition ◽  
Design Methodology ◽  
Noise Control ◽  
Noise Source ◽  
Free Field ◽  
Active Noise Control ◽  
Active Noise ◽  
Enclosed Space ◽  
Experimental Design Methodology

Abstract The purpose of this paper is to propose an experimental design methodology for global active noise control in an enclosed space. We aim to control the noise caused by an internal noise source. Since each enclosed space has different acoustic characteristics, it is difficult to design different controllers suitable for each enclosed space. So, we decided to design a controller that could be used universally. The basic concept is the collocation of noise source and control speakers to generate a sound field opposite in phase to the noise source in a free field. For implementation of the proposed method, we propose a configuration method of control speakers and error microphones, and an active noise control algorithm. Also, to confirm the applicability of the proposed method, we design a controller in an anechoic chamber, which represents a free field condition, and perform active noise control in other enclosed spaces with the controller designed for the anechoic chamber. The experimental results show that the solution calculated in the free field condition can be used in other enclosed spaces without any modifications.

scholarly journals Experimental investigation on the potential of the Feedback Fx-LMS Active Noise Control technology for use in industrial generator sets

2021 ◽  
Vol 312 ◽  
pp. 08007
Author(s):  
Marco Ciampolini ◽  
Lorenzo Bosi ◽  
Luca Romani ◽  
Andrea Toniutti ◽  
Matteo Giglioli ◽  
...  
Keyword(s):  
Acoustic Waves ◽  
Noise Control ◽  
Noise Source ◽  
Acoustic Noise ◽  
Active Noise Control ◽  
Lms Algorithm ◽  
Destructive Interference ◽  
Exhaust Pipe ◽  
Least Mean Square ◽  
Active Noise

Active Noise Control (ANC) has been considered a promising technology for the abatement of acoustic noise from the mid-20th century. Feedback and Feedforward ANC algorithms, based on the destructive interference principle applied to acoustic waves, have been developed for different applications, depending on the spectrum of the noise source. Feedback ANC algorithms make use of a single control microphone to measure an error signal which is then employed by an adaptive filter to estimate the noise source and generate an opposite-phase control signal. The Fx-LMS (Filtered-X Least Mean Square) algorithm is mostly adopted to update the filter. Feedback ANC systems have proven to be effective for the abatement of low-frequency quasi-steady noises; however, different challenges must be overcome to realize an effective and durable system for high-temperature application. This paper aims at experimentally assessing the feasibility of a Feedback Fx-LMS ANC system with off-line Secondary Path estimation to be used in mid-size diesel gensets for the reduction of the exhaust noise. Several solutions are proposed, including the mechanical design, the development of the Fx-LMS algorithm in the LabVIEW FPGA programming language, and the key features required to prevent parts from thermal damage and fouling. The developed prototype was implemented on a 50-kW diesel genset and tested in a semi-anechoic chamber. The noise abatement inside the exhaust pipe and at different measurement points around the machine was evaluated and discussed, showing good potential for improving the acoustic comfort of genset users.

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