Noise Reduction in Ducts Achievable by Point Control

1998 ◽  
Vol 120 (2) ◽  
pp. 216-223 ◽  
Author(s):  
K. A. Morris
Keyword(s):  
Noise Reduction ◽  
Closed Loop ◽  
Noise Control ◽  
Active Noise Control ◽  
Practical Interest ◽  
Noise Levels ◽  
Sensors And Actuators ◽  
One Dimensional ◽  
Active Noise ◽  
Point Control

Noise control in a one-dimensional duct is analyzed. This problem is of practical interest and is also simple enough that a complete theoretical analysis is possible. It is shown that the optimal controller leads to an unstable closed loop. The noise reduction level achievable with a stable closed loop is calculated for arbitrary choices of sensor and actuator locations. This enables the best placement of sensors and actuators to be determined. Also, the analysis indicates that a “spatial waterbed” effect exists in some configurations of active noise control: i.e., that noise levels are increased for points outside of the region over which the design is done.

Global Active Noise Control of a One-Dimensional Acoustic Duct Using a Feedback Controller

1993 ◽  
Vol 115 (3) ◽  
pp. 488-494 ◽  
Author(s):  
A. J. Hull ◽  
C. J. Radcliffe ◽  
S. C. Southward
Keyword(s):  
Noise Level ◽  
Noise Control ◽  
Acoustic Noise ◽  
Active Noise Control ◽  
Decay Rates ◽  
Pole Placement ◽  
Noise Levels ◽  
One Dimensional ◽  
Active Noise ◽  
System Pressure

Active noise control of acoustic enclosures is a classical engineering problem. The active noise control of a one-dimensional hard-walled duct with a partially dissipative boundary condition is addressed in this paper. Previous techniques have attacked this problem by developing adaptive filters designed to cancel acoustic noise at a single measurement location. The work presented here applies modern, state space, control theory to globally reduce noise levels in a one-dimensional acoustic enclosure rather than at a single location. This global control requires only the addition of a single response measurement microphone and control speaker to the open-loop system. Pressure measurements are taken at the microphone location and passed to an observer, which generates estimates of the system states. Using these state estimates, a pole placement feedback control algorithm is used to lower the noise level. Pole placement reduces noise levels globally by increasing the decay rates of all the controlled acoustic states. Experimental results presented here demonstrate reduction in the noise level at all points in the duct by 58 percent when the system is excited by random amplitude pressure input.

Role of Acoustic Properties in Biomedical Active Noise Control

2020 ◽  
Vol 9 (1) ◽  
pp. 48-60
Author(s):  
Sajil C. K. ◽  
Achuthsankar S. Nair
Keyword(s):  
Numerical Simulation ◽  
Biomedical Applications ◽  
Noise Control ◽  
Active Noise Control ◽  
Acoustic Properties ◽  
Reflection Coefficients ◽  
Sensors And Actuators ◽  
Active Noise ◽  
Source Signal

Active noise control (ANC) systems are tailored for user-specific scenarios which are required in biomedical applications due to the physical restrictions in the placement of sensors and actuators. This study examines the role of spectral flatness of acoustic channels and room reflection coefficients in ANC performance. Each room has a unique characteristic response in transforming a source signal. By employing preliminary measurements and numerical simulation, the authors show that improved noise control is possible by optimizing room reverberation and spectral flatness of the secondary acoustic channel. This result has potential application in improving existing ANC systems in biomedical applications like fMRI.

Coherence-based performance analysis on noise reduction in multichannel active noise control systems

2020 ◽  
Vol 148 (3) ◽  
pp. 1519-1528
Author(s):  
Jihui Aimee Zhang ◽  
Naoki Murata ◽  
Yu Maeno ◽  
Prasanga N. Samarasinghe ◽  
Thushara D. Abhayapala ◽  
...  
Keyword(s):  
Performance Analysis ◽  
Noise Reduction ◽  
Control Systems ◽  
Noise Control ◽  
Active Noise Control ◽  
Active Noise

Active Feedback Control Using Adaptive Filtering

2004 ◽  
Vol 10 (1) ◽  
pp. 25-38
Author(s):  
Fenglin Wang ◽  
Chris K Mechefske
Keyword(s):  
Feedback Control ◽  
Closed Loop ◽  
Noise Control ◽  
Active Noise Control ◽  
Experimental Studies ◽  
Loop Control ◽  
Active Noise ◽  
Active Feedback ◽  
Loop Control System ◽  
Active Feedback Control

In this paper we apply a filtered-X algorithm to an active feedback control structure and derive the transfer function of a closed-loop control system. Simulation studies are then carried out on the closed-loop property while varying the parameters (input frequency, delays in plant, amplitude and phase of modeling filter). Several properties of adaptive feedback control are revealed. Experimental studies on feedback active noise control of noise in a finite duct and a small enclosure are described, and outstanding active noise control effects are achieved. Experimental results of closed-loop frequency response are also provided.

Estimate of aircraft flyover noise reduction by application of active noise control to engine fan tones

1997 ◽  
Author(s):  
R. Kraft ◽  
B. Janardan ◽  
P. Gliebe ◽  
R. Kraft ◽  
B. Janardan ◽  
...  
Keyword(s):  
Noise Reduction ◽  
Noise Control ◽  
Active Noise Control ◽  
Active Noise
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