Final Rev1

8/2/2019 Final Rev1

http://slidepdf.com/reader/full/final-rev1 1/18

Arpan G

Srikanta Bhatta B S

Guided By Prof.P Meena

8/2/2019 Final Rev1


ACTIVE NOISE CANCELLATION

It uses the phenomenon of wave interference.Two waves with same amplitude and frequency butphase-reversed travelling in the same direction willneutralize each other.The resulting sound is ideally null, as sound energy istransformed into heat.

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Basic ANC System

The components of ANC system are

• Noise source

• Reference MIC

• Control speaker

• Error MIC

ANC controller whichis an adaptive LMSfilter.

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Noise Cancellation Using LMS

algorithm Lms adaptive filter

y(n)= xT(n)w(n)

Update weights: w(n+1)= w(n) + me(n)x(n)m: step size

e(n)= d(n)-y(n)

x(n) : refrence signal

y(n): filter output

d(n): desired output

e(n):error signal

Convergence depends on step size

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SIMULATION

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COMPOMENTS NOISE SOURCE

DESIRED RESPONSE

LMS FILTER

ERROR SIGNAL

SUBTRACT

DELAY

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FIRLMS

Arguments

h[nh] Coefficient Array

x[nh] Input Array

b Error from previous FIR

nh Number of coefficients

return long return value

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ALGORITHMlong firlms2(short h[ ],short x[ ], short b, int nh){int i;

long r = 0;for (i = 0; i < nh; i++){

h[i] += (x[i] * b) >> 16;r += x[i + 1] * h[i];

}return r;}

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SUBTRACT The Subtract block performs the function of destructive

interference that happens in the real world.

DELAY The Unit Delay block delays its input by the specifiedsample period. This block is equivalent to the z-1 discrete-time operator. The block accepts one input and generatesone output, which can be either both scalar or both vector.

If the input is a vector, all elements of the vector aredelayed by the same sample period.

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http://slidepdf.com/reader/full/final-rev1 10/18Spectrum analysis of noise

8/2/2019 Final Rev1

http://slidepdf.com/reader/full/final-rev1 11/18Spectrum analysis of the output

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Hardware implementation Hardware used: Texas Instruments TMS320C6713

DSK and AD6M daughter card.

Daughter card needed due to the drawbacks of DSK

DSK kit has only 1 ADC.

Features of TMS320C6713 225 MHz CPU

16 MB sync RAM and 512 Kb Flash

Standard expansion for Daughter Cards

JTAG emulation

Single +5v supply

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C6713 DSK board

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AD6M Daughter Card

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TESTING & WORKING Initially Model implemented in SIMULINK

The model is automatically downloaded onto the DSK

CCS generates C code, emulates onto the Hardware. Many disadvantages with this method.

Feasibility is reduced.

Customizations are not possible.

Simulink generates errors

The daughter card can’t be accessed.

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Solution

We write our own C code The model is emulated directly

Progress Studying in detail the aspects of Hardware

Programming

Implemented some basic codes for testing purposes

Implemented the static model of our project i.e.,, nonreal time model but outputs are not according to ourexpectations.

Further things to be done Implementation of real time model

Design of ducts, enclosures and microphoneplacements.

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8/2/2019 Final Rev1


THANK YOU

Final Rev1

Documents

Transcript of Final Rev1