There are different areas for information on active noise reduction.
By the usageof signal processors it has became possible to utilize different activenoise control methods.
Noise suppression using active noise control and masking.
The third problem formulated is the active control of enclosed or partially enclosed harmonic sound field where the noise source strengths of enclosure boundary description may not be known.
Figure 1.1: Destructive interference example Active control systems are able to operate at low frequencies, where passive meth- ods are ine�'ective: moreover, the reduction is achieved without physical modiﬁcation
or rearrangement of existing noise sources.
Péceli, “Active noise control - simulation in MATLAB”,
The Literature 34 Figure 2.1: Dual ANC system setup The choice of the latter one relies on a Silentium�''s S-Cube�'� controller running an FxLMS algorithm: an interlaced Echo Cancellation algorithm is added for taking care
of the echo issues, due to the fact that each microphone picks up signals from both
 proposes a combination of passive and active noise control to at-
tenuate the noise produced by a 90 �'90�'20 mm fan positioned at the midpoint of a 440 mm-long duct, whose cross-section is designed to avoid obstructing the air�'ow,
thereby not lowering the cooling performance.
(2000) "Active noise control primer" AIP Press.
(2004) "Optimal Transducer Positions of an Active Noise Control System with an Opening in an Enclosure" Journal of The Korean Society for Noise and Vibration Engineering, 14(2), pp.
Active noise control is a possibility forefficient noise suppression, even if the spectra of the speech and thenoise are overlapped in the frequency domain.
Please contact the supervisor for more details.
The Impact of Subsonic Twin Jets on Airport Noise
Conventional linear filtering, control or prediction techniquesare used to cancel or reduce the noise.
Active Control of Discrete-Frequency Noise from Small Subsonic Fans
(2006)Adaptive Resonant Mode Active Noise Control. Master's Thesis, University of Pittsburgh. (Unpublished)
Active Noise Control of Low Frequency Sound Inside Enclosures
high temperature) of the possible acoustic systems, the active noise controlsystem needs special hardware tools.
Active Attenuation of Acoustic Noise Using Adaptive ARMAX Control
Active Noise Control 26 1.1 Algorithms for ANC Figure 1.2: LMS block diagram The most common adaptive algorithm is the Least Mean Square (Fig.1.2): it is able to identify a ﬁlter, whose a-priori impulse response h(n) is unknown, by the
approximation of a secondary ﬁlter, W (n).
Active control of axial-�'ow fan noise.
Active Noise Control 27 Figure 1.3: FxLMS block diagram �'� the acoustic channel between the actuator and the cancellation area and the one between this area and the error microphone.
A compact active control implementation for axial cooling fan noise.
Active Noise Control 25 �'� the controller, that is, the signal processor which tells the actuators what to do, on the basis of sensors�'' signals and the knowledge of how the plant responds
to the actuators (FPGA).
Active control of axial-�'ow fan noise using magnetic bearings.
Active Noise Control 28 1.2 Operative principles By looking at the standard ANC system in Figure 2 (see Introduction), it is evident that three major issues has to be solved: the position of the reference microphone,
the position of the error one and that of the canceling loudspeaker.
On the use of magnetic bearings for global control of fan noise.
the physical system to be controlled (the DVBT device in this case of study); �'� the sensors, to sense the disturbance and to monitor how well the system is performing (microphones); �'� the actuators, the devices which do the work of altering the plant response (loudspeakers); 24 Chapter 1.
Active noise control systems, 1996.
The acoustic characteristics of the noise source and the environment are usually time varying; in addition, the frequency content, amplitude, phase and sound velocity
of the undesired noise are non-stationary.
"I have always been impressed by the quick turnaround and your thoroughness. Easily the most professional essay writing service on the web."
"Your assistance and the first class service is much appreciated. My essay reads so well and without your help I'm sure I would have been marked down again on grammar and syntax."
"Thanks again for your excellent work with my assignments. No doubts you're true experts at what you do and very approachable."
"Very professional, cheap and friendly service. Thanks for writing two important essays for me, I wouldn't have written it myself because of the tight deadline."
"Thanks for your cautious eye, attention to detail and overall superb service. Thanks to you, now I am confident that I can submit my term paper on time."
"Thank you for the GREAT work you have done. Just wanted to tell that I'm very happy with my essay and will get back with more assignments soon."