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Done By:
Samah Qissy Areej EL-MidanaSereen Essraj Ghadeer Abu-safer
Submitted To:
Dr. Hatem El-Aydi
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Contents.
What is noise?
What is noise cancellation?
Simple idea.
Wave cancellation.
Active noise cancellation (ANC).Applications.
Adaptive filter.
Comparison
Adaptive algorithm (LMS & RMS).
Simulation.
Conclusion.
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What is noise?
Fiq(1):AWGN
Noise consists of unwanted waveforms that
can interfere with communication.
sound noise: interferes with your normal
hearing
Loud noises
Subtle noiseWhite noise (AWGN)
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Active and passive noise
The advantages of active noise control methods
compared to passive ones are that they are
generally:
More effective at low frequencies.
Less bulky.
Able to block noise selectively
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What is Noise Cancellation?
Noise cancellation is a method to reduce or
completely cancel out undesirable sound
call Active Noise Cancellation .
Noise cancellation tries to 'block' the sound atthe source instead of trying to prevent the
sounds from entering our ear canals
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Cont.These technologies are in their early stages.
The hope is that one day that thesetechnologies can be used to minimize all sorts of
unwanted sounds around us
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Simple Idea
Cancellation processes depend on simpleprinciple
adding two signals with the same .
amplitude and opposite phase the result
will be zero signals.
(H)
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Questions you may have about
such a device are:
How can you cancel out simple waveforms?
How is complex sound cancelled out?
What are some noise cancellation applications?
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Types of wave cancellation
wave cancellation
Simple wave complex wave
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Simple wave cancellation
Simple sine wave for single
sound frequencyOne pure sound a fraction of
a second after the next
Sum of two waves
slightly out of phase
Sum of two waves slightly
out of phase
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Canceling complex waves
A spoken word consists of a
spectrum of frequencies of
different amplitudeneed to filter each
frequency separately,
create the same frequencyand amplitude at 180out of
phase.
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Active Noise Cancellation (ANC)
http://focus.ti.com/vf/docs/viewdevices.tsp?blockDiagramId=6048&blockId=6581&designOptionId=6644&family=vfhttp://focus.ti.com/vf/docs/viewdevices.tsp?blockDiagramId=6048&blockId=6581&designOptionId=6644&family=vfhttp://focus.ti.com/vf/docs/viewdevices.tsp?blockDiagramId=6048&blockId=6582&designOptionId=6646&family=vfhttp://focus.ti.com/vf/docs/viewdevices.tsp?blockDiagramId=6048&blockId=6587&designOptionId=6647&family=vfhttp://focus.ti.com/vf/docs/blockdiagram.tsp?family=vf&blockDiagramId=6048http://focus.ti.com/vf/docs/viewdevices.tsp?blockDiagramId=6048&blockId=6588&designOptionId=6648&family=vfhttp://focus.ti.com/vf/docs/viewdevices.tsp?blockDiagramId=6048&blockId=6583&designOptionId=6649&family=vfhttp://focus.ti.com/vf/docs/viewdevices.tsp?blockDiagramId=6048&blockId=6584&designOptionId=6650&family=vfhttp://focus.ti.com/vf/docs/viewdevices.tsp?blockDiagramId=6048&blockId=6585&designOptionId=6651&family=vfhttp://focus.ti.com/vf/docs/viewdevices.tsp?blockDiagramId=6048&blockId=6586&designOptionId=6652&family=vfhttp://focus.ti.com/vf/docs/viewdevices.tsp?blockDiagramId=6048&blockId=6589&designOptionId=6653&family=vf -
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ApplicationsHeadsets (headphone)
Honda cars.
Space satellite antennas.
Use in apartment.
.NoiseMuter
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NoiseMuter)Noise Canceller(
NoiseMuter ProcessedOriginalCondition/coder
NoiseMuter
processed
OriginalSpeech + Car
Noise
NoiseMuter is an advanced noise suppressionsolution, designed as add-on software module to
enable noise-free communication.
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Adaptive filter
nonlinear and time-variant .
adjust themselves to an ever-changingenvironment .
changes its parameters so its performanceimproves through its surroundings.
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Adaptive Filter
The coefficients of an adaptive filter change
in time
Output
signalInput
signal
Adaptive
algorithm
Criterion of
performance
Filter
structure
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Comparisonsupervised vs. unsupervised
Expected output is known.
quantity .
The Criterion of
Performance can simplytake the difference
between actual output and
desired.
It uses information to tell
the Adaptation Algorithm
what adjustments to make.
Expected output is
unknown quantity.
the Criterion of
Performance has to do.
We cannot simply take
the difference actual anddesired output consists
of looking for signal
qualities
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Block diagram of adaptive system
S(n)+No(n)No(n)
+
-
?
Primary
signal
d(n)
N1(n)
Reference
signaly(n)
output
e(n)
adaptive
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Adaptive algorithm
An adaptive algorithm is used to estimate a timevarying signal.
By adjusting the filter coefficients so as tominimize the error.
There are many adaptive algorithms likeRecursive
Least Square (RLS), Kalman filter, but the most commonly used is the Least Mean
Square (LMS) algorithm.
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LMS algorithm
Estimates the
solution to the
Weiner-Hopf
equations using
gradient descent
method which finds
minima by estimating
the gradient.
is the step size
e
X(n)
C(n)
Transversal
Filter
LMS
Y(n)
e(n)
d(n)
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Cont..
Update the coefficients using
the following computation.
filtering operation with the
previous version of the coefficients.
Compare the computed output
with the expected output.
e(n)
X(n) y(n)
d(n)
Adaptive
filter
Unknown
system
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Experiment
Click to listen original sound Click to listen nosily sound
Click to listen output1 sound
Click to listen output 2 sound
click to show simulation graph1
Click to show simulation graph
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Why using RLS algorithm
Increase performance .
Faster convergence behavior.
Infinite memory
Improve the final noise removal
performance.
Filter coefficient is much more stable .
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conclusion
Active noise cancellation is a method to cancel
out undesirable sound in real time.
The adaptive filter is used to estimate the errorin noisy wave
Many algorithms are used in adaptive filter like
LMS RLS & MSE and the better is RLS .
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