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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 .