Active Noise Cancellation

1
Active Noise Cancellation

• Dr. Farrukh  
• Department of Electrical Electronics
  Engineering,
• College of Engineering,
• University Tenaga Nasional,
• Jalan Kajang-Puchong,
• 43009 Kajang,
• Selangor, MALAYSIA.
• Farrukh_at_uniten.edu.my

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Description of paper

• Use of TMS320C5402 DSK-single TMS320C6701 EVM
  dual channel channel Active Noise Cancellation in
  duct system
• Uses feedback feedforward topology -designed to
  cancel narrowband periodic tones.

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Problem Description!!!!
What is Noise ?????

• Unwanted sound that
• is often loud and irritating
• Industrial equipment
• Damaging to human from both
• a physical and psychological aspect

Active Noise Cancellation???
Reason
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How does Active Noise Cancellation (ANC) works ?

• Identical and in phase
• Volumes increases

• Out of phase
• Volumes decreases

Active noise cancellation

• Basic principles by introducing a canceling
  anti-noise signal that has the same amplitude but
  the exact opposite phase and resulting a
  reduction noise signal

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Approaches of ANC
Hardware

• Feedforward Topology
• Reference noise and
• cancelled noise are used
• 2 inputs and 1 output

• Feedback Topology
• only cancelled noise
• are used one input and one output
• Use of TMS320C5402 DSK-single
• channel Active Noise Cancellation
• in duct system

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Feedback Topology
Hardware
x(n)
e(n)

• to estimate primary
  noise and use it as a reference

X(z) E(z) S(z)Y(z)
Duct system
y(n)

• Need to estimate the secondary path transfer
  function

W(z)
S(z)
L MS
y(n)
x(n)
DSP System
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Feedback Experimental Setup-ANC
Hardware
Noise loudspeaker
S(z)
x(n)
e(n)
Amplifier
Secondary Path
IN
OUT
y(n)
LMS Algorithm
DSP TMS320C5402 DSK
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Feedforward Topology
x(n)

• Coherent input is captured, filtered and feed
  into LMS

e(n)
d(n)
Primary function, P(z)
y(n)
Secondary Path,S(z)
Duct system

• Estimation of the secondary path transfer
  function is obtained by identification process

y(n)
W(z)
Estimation of S(z), S(z)
LMS
e(n)
x(n)
DSP System
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Feedforward Experimental Setup
Hardware
Canceling zone
Noise speaker
microphone
x(n)
S(z)
e(n)
Secondary Path
Input noise
y(n)
Canceling speaker
Amplifier
TMS320C6701 EVM DSP
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Least Mean Square (LMS) Algorithm
Software
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Secondary path S(z) duct modeling
Result of identification of the secondary path
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Single channel cancellation results
Input Frequency 120Hz
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Cancellation result on 7080100110120130Hz
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Dual Channel cancellation Results
Input Frequency 80Hz
No cancellation With cancellation
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Input Frequency 4070Hz
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Cancellation result on 40 70 80Hz
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Conclusions

• ANC was first time attempted in Malaysia and
  obtained compatible results.
• Integrated programming of DSP was achieved
  without any external aid or training.
• This work yields Masters thesis and research
  papers accepted by local and international
  conferences.
• The expertise developed is now being shared with
  other groups, projects and laboratory work in COE.

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Future Scope

• Acoustic wave propagation in duct boundary is
  investigated with PDE Finite Element method will
  be the future direction
• Boundary value conditions at the exhaust of duct
  can be studied with FEM
• Build dedicated DSP hardware for embedded
  standalone ANC system
• PCB for audio amplifiers and speakers are needed
  for mobility of test rig

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FINITE ELEMENT METHOD ANALYSIS OF DUCT SYSTEM
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ACCOUSTIC ENERGY INSIDE THE DUCT
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The end