Design of An Active Noise Reduction System (Mechanical Engineering)

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Design of An Active Noise Reduction System
(Mechanical Engineering)
UNITED ARAB EMIRATES UNIVERSITY College of
Engineering Graduation Projects Unit

• Students
• Mohammed Saber Bou-said 200106411
• Khaled Ahmad Ashoor
  200001533
• Advisor Dr. Farag K. Omar

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Preview

• Noise to be reduced to an acceptable level in a
  desired area.
• Designing an ANC system that contains
  Microphones
• Microphones
• Speakers
• Processor
• GPII produce a working prototype of our designed
  system.

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Content

• Theory
• Steps performed in GPI
• Steps performed in GPII
• Case study
• Components Specifications
• Alternatives for Processing
• System Integration
• System testing
• System development based on the testing feedback

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Theory ANC (general)

• Introduction, benefits
• Theory of noise canceling
• by wave superposition

• Applications of active noise control
• Headsets
• Industrial fans
• AC ducts

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Theory ANC (Technical)

• The different techniques of Active Control
• Main components of ANC systems

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Theory Application

• Bedroom or office
• A fan producing undesirable noise
• Noise cancellation through ANC

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GPI Summary

• Literature review Background Information
• Defining application properties
• Application Selection
• Properties of Noise, Area, Fans
• Defining constraints and limitations
• Comparing alternatives Components and placement
• Design simulation
• Room Modeling
• Evaluation of the possibility of noise reduction
  at users area

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Case Study

• A student from electrical engineering made a
  project of a sound recorder
• Part of this project was interesting for our
  project.
• Helps to define the main components of the
  processing part of the system.

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Case

• Project during industrial training
• storing sound taken by a microphone into a memory
• playing it through headphones when playback mode
  selected
• A/D after Microphone, D/A before speaker
• Microprocessor and program in between

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Buffers processing

• Buffers may be used after taking original noise
  and after processing
• This is better than using a DAC and PC
• High speed of processing
• Low probability of interruption
• Fast processing
• To avoid adding another delay
• To ensure a good response time for the system

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Components Specifications

• Components
• Microphone
• Speaker
• A/D D/A
• Processor
• Specifications depending mainly on noise
  properties
• Some types of noise recorded and evaluated

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Kitchen Fan Noise

• Main frequencies 21.9, 41.9, 62.9, 83.8, 104.22,
  125.8, 145.8, 167.5, 184.5, 209.3, 228.9, 251.5,
  272.4Hz
• Considerable harmonics up to 300 Hz
• Range of frequency for this noise 20,300.

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Office Fan Noise

• Major frequencies 16.7, 22.5, 45.2, 67.7, 89.9,
  113, 134.8, 157.7
• The range of frequency for this noise 15, 250

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System Specifications Mic.

• Frequency range 15, 1500
• Output suitable for the processor, mostly -5,
  5V
• Microphone called "tie-clip microphone"
• Speaker compatible with these specifications

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Digital Signal Processor

• Maximum frequency 500Hz
• Sampling frequency must be at least 3 KS/s
• Continuous Data taking

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Processor

• Basic wave f20Hz, T1/20 0.05s 50ms
• Harmonics f500Hz, T1/500 0.002s 2ms
• Delay step 0.5ms, up to 25ms
• "Digital Delay Line containing A/D and D/A
  converters

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Single Chip Digital Delay IC
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Processing Methods

• A stand alone microprocessor chip with all
  required input output circuits
• A digital delay chip integrated with DAC and
  controlled by LabView
• A PCI card and LabView VI
• A PC sound card with a LabView VI

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Alternative No.2
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Alternative No.3 (DAQ LabView)

• Installing LabView on the PC
• Installing Card Drivers on the PC
• Assembling the DAQ inside the PC
• Configuring testing through provided utility
  program. Two tests
• Analog input test
• Analog output test

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Analog Input Analog Output

• LabView VI
• function generator with the DAQ through the input
  channel.
• Input is processed by the VI
• To oscilloscope through AO channel.

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Sinusoidal Wave

• Sinusoidal sound wave generated by function
  generator
• Process multiplication by -1
• Output through AO channel to speaker
• Physical delay by moving actuator

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Results
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Wave Delay Control VI
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Operation with Real Noise

• A fan noise recorded 10 minutes, then played from
  a separate PC through a speaker. -------gtsource
• Actuators placed near the source, as well as the
  reference microphone
• Basic microphone sensing noise
• The delay tuned from the LabView VI user
  interface
• Sound pressure level monitored using a SPL meter
  placed at 3meters from the source.

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Band Filter
Mic.
DAQ
Processor ( LabView) Ability to add gain
(instead of amplifier)
Speaker
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Results
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Conclusion

• Engineering design projects Procedure followed.
• Noise reduction practically possible using wave
  superposition.
• Difficulties lower expectation
• complete prototype of an active noise reduction
  system built, including
• Reference microphones to collect noise data.
• Signal processing electronic circuits (amplifier,
  low-pass filter, etc)
• Configured data acquisition system (Data
  acquisition card, PC and software code)
• Output signal processing circuit.
• Output speaker
• Sound level meter to measure noise level at and
  around the user's location.

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Thanks for Listening