The Mechanisms of Passive Ear Defenders

2002 ◽  
Vol 33 (5) ◽  
pp. 13-21 ◽  
Author(s):  
M. R. Paurobally ◽  
J. Pan
Keyword(s):  
Sound Absorption ◽  
Theoretical Study ◽  
Active Noise Control ◽  
Low Frequency ◽  
The Other ◽  
Frequency Noise ◽  
Transmission Characteristics ◽  
Active Noise ◽  
Theoretical Predictions

In this paper a model of the sound transmission characteristics of a conventional circumaural passive ear protector is presented for low frequency noise. It includes the effects of porous sound absorption material within the device as well as sound leakage. A theoretical study based on the model shows that the presence of sound absorption material effectively acts to increase the volume compliance of the system, thus decreasing its resonance frequency. The role of leakage on the other hand is mainly to shift the resonance to a higher frequency depending on the equivalent leakage diameter. Experimental results are provided in support of the theoretical predictions. The model is useful in providing an understanding of the mechanisms of conventional passive ear defenders and can be employed to guide their design. The modelling can also be extended to study and aid in the development of communication and active noise control ear protectors.

scholarly journals Active Structural Acoustic Control of an Active Casing Placed in a Corner

2019 ◽  
Vol 9 (6) ◽  
pp. 1059 ◽  
Author(s):  
Anna Chraponska ◽  
Stanislaw Wrona ◽  
Jaroslaw Rzepecki ◽  
Krzysztof Mazur ◽  
Marek Pawelczyk
Keyword(s):  
Active Noise Control ◽  
Low Frequency ◽  
Frequency Noise ◽  
Noise Emission ◽  
Sound Sources ◽  
Low Frequencies ◽  
Emission Efficiency ◽  
Active Noise ◽  
Acoustic Control ◽  
Device Noise

Electric appliances used in workplaces and everyday life often generate a low-frequency noise, which affects human body systems. Passive methods employed to reduce noise are not effective at low frequencies. The classical approach to active noise control practically involves the generation of local zones of quiet, whereas at other areas the noise is reinforced. Moreover, it usually requires a large number of secondary sound sources. Hence, an active casing approach has been developed. The active casing panels’ vibrations are controlled to reduce the device noise emission. Efficiency of this method has been previously confirmed by the authors and the results have been reported in multiple journal publications. However, in the previous research experiments, the active casing was placed at a distance from the enclosure walls. In this research, the active casing is located in a corner and such placement is intentionally used to facilitate the active control system’s operation. The noise reduction performance is investigated at multiple configurations, including a range of distances from the corner and different error microphone arrangements. The analysis of both primary and secondary paths is given. Advantages and drawbacks of different active casing configurations are presented and discussed.

Adaptive Active Control System of Vehicle Noise Design and Test

2014 ◽  
Vol 1028 ◽  
pp. 251-256 ◽  
Author(s):  
Ji Guang Jiang ◽  
Yue Zeng
Keyword(s):  
Active Noise Control ◽  
Low Frequency ◽  
Control Unit ◽  
Noise Signal ◽  
Frequency Noise ◽  
Low Frequency Noise ◽  
Power Module ◽  
Vehicle Interior ◽  
Vehicle Noise ◽  
Active Noise

According to the vehicle interior low frequency noise existing, vehicle interior adaptive active noise control strategy is established based on the FXLMS algorithm, designed the core circuit module active noise controller, including the vehicle interior noise signal amplification module, a main control unit, audio power amplifier module and power module, completed development of the controller hardware, and programming the control software system; using this system, on vehicle driving conditions vice driver left ear position low frequency noise cancellation control in the steady state, the 8.5 dB (Lin) and 10.2dB (Lin) the amount of noise reduction.

Experimental Study on an Active Noise Control System for Turboprop Driven Aircraft

2013 ◽  
Vol 333-335 ◽  
pp. 2142-2145
Author(s):  
Qing Fu Kong ◽  
Yu Liang Dai ◽  
Shi Jian Zhu ◽  
Jia Ming Wu
Keyword(s):  
Experimental Study ◽  
Control System ◽  
Sound Source ◽  
Noise Control ◽  
Active Noise Control ◽  
Low Frequency ◽  
Frequency Noise ◽  
Low Frequency Noise ◽  
Experimental Platform ◽  
Active Noise

In order to find a solution to the control of low frequency noise in the cabin of turboprop driven aircraft, an experimental active noise control (ANC) system is introduced in the paper, which consists of vibroacoustic field analogue subsystem, acoustic field measurement subsystem and acoustic barrier exciter subsystem. Effects of both different spaces between the primary sound source and secondary sound source of the ANC system and different frequency noises on noise-reduction result are investigated based on the experimental platform. Results of the experiment show a significant potential of the ANC method for the control of low frequency noise in the cabin of turboprop driven aircraft.

Simulation of Active Noise Control System on the Truck Interior Cab

2013 ◽  
Vol 798-799 ◽  
pp. 443-447
Author(s):  
Qi Chen LU ◽  
Hui Bin LI ◽  
Hua Huang
Keyword(s):  
Control System ◽  
Control Systems ◽  
Active Control ◽  
Noise Control ◽  
Active Noise Control ◽  
Low Frequency ◽  
Frequency Noise ◽  
Simulink Model ◽  
Active Noise ◽  
Active Control System

Studying on adaptive active noise control (AANC) system of the truck interior cab to reduce the low-frequency noise,a normalization FLMS algorithm simulink model is established in Matlab/Simulink.Then taking it as the core,a feedforward adaptive active control system and a feedback adaptive active control system of the tuck interior cab are established in Matlab/Simulink .Considerating the actual error channels effects on systems ,the noise reduction effects of two adaptive active control systems are verified from the simulintion results.Through comparing the two wo adaptive active control systems,we found that the feedforward adaptive active control system is more stable.

scholarly journals Application Study of Adaptive Tracking Algorithm in Active Noise Control System of Transformer

2019 ◽  
Vol 9 (13) ◽  
pp. 2693 ◽  
Author(s):  
Liming Ying ◽  
Jinwei Wang ◽  
Qin Liu ◽  
Donghui Wang
Keyword(s):  
Noise Reduction ◽  
Noise Control ◽  
Spectral Characteristics ◽  
Active Noise Control ◽  
Low Frequency ◽  
Cost Effective ◽  
Frequency Noise ◽  
Low Frequency Noise ◽  
Active Noise ◽  
Reduction Methods

Active noise control (ANC) technology can be able to reduce the low frequency noise effectively, and has been widely applied in limited enclosed equipment, such as cars, aircraft cockpits, and headphones, etc. Compared with the traditional noise reduction methods, ANC technology is a cost-effective method in handling the low-frequency noise of transformers. An experimental ANC system in a virtual substation is designed and constructed. An adaptive signal tracking ANC algorithm is proposed, and a set of ANC experimental prototypes applied to a virtual substation is designed. Based on the proposed algorithm, the distributions of the acoustics and spectral characteristics of transformer noise in substations are analyzed. Experimental results show that the effective noise reduction can be achieved an average of 5 dB(A) in a given region with respect to the absence of the ANC system.

Development of Engine Exhaust Active Noise Control System

2014 ◽  
Vol 986-987 ◽  
pp. 1196-1200
Author(s):  
Jie Wang ◽  
Zhi En Liu ◽  
Jia Wei Zeng ◽  
Chao Wang
Keyword(s):  
Control System ◽  
Noise Control ◽  
Active Noise Control ◽  
Low Frequency ◽  
Signal Acquisition ◽  
Frequency Noise ◽  
Low Frequency Noise ◽  
Engine Exhaust ◽  
Voice Signal ◽  
Active Noise

In order to enhance the capacity of elimination of engine exhaust low frequency noise, a set of engine exhaust active noise control system was developed. The system was developed by using MC9S12XS128 MCU, and it is based on the theory of sound wave interference. The system can realize the voice signal acquisition, reverse phase processing and output, and can eliminate engine exhaust low frequency noise. Experimental results showed that the system has good silencing effects on the engine exhaust noise under the steady state.

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