Acoustic Beamformer

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Midway Design Review
Team Acoustic Beamformer
11/25/2013
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Team Acoustic Beamformer
Name
Jimmy Danis EE
Nick Driscoll EE
Rebecca McFarland CSE
John Shattuck EE
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Project Goal

• Objective scan and localize a single persons
• voice among outside conversation and background
  noise
• in real time
• Primary Use conference rooms (teleconferences)
• Secondary Uses small lecture halls, security
• Other Moral Implications

• Help increase conference/lecture productivity
• Can help the hard of hearing

• Could act as an eavesdropping device

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Specifications

• Operating range minimum 1m, maximum 3m
• Minimum spanning angle range 130 degrees
• Gives us a scanning distance of at least 2.27
  meters at minimum distance
• Can comfortably fit 3 people for a teleconference
  call within this range
• Typical width of meeting room chairs 47cm
• Can allow 43cm spacing between participants
• Minimum Beamwidth 38.1 (to not intercept both
  voices in main beam)
• Operate within the human voice frequency spectrum
• Ideally 300 Hz- 3kHz

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Updated Block Diagram
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Narrowing the Frequency Range
Phonetic Vowel ?

• Look at Phonetic Vowels
• Have distinct peaks in magnitude across the
  frequency range known as formants
• First is highest in magnitude, provides a low
  frequency window

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Current System Specifications

• Mic spacing 24cm

F450Hz
BW61
BW52
BW61
F680Hz
BW50
BW34
BW50
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Design Flaws to Be Addressed

• May not be a worry in considering the magnitudes
  within our beam

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A/D Choice

• Selected the MC DAQ USB-204
• System Requirements
• 8 channels
• gt30 kHz Sample Rate
• USB Interface
• USB-204 Specifications
• 8 channel analog I/O
• 500 kHz total sample rate, 62.5 kHz/channel
• 12-bit depth
• USB 2.0 Full Speed (12 Mbps)
• (240 kHz 12 bits 2.88 Mbps)

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Microphones

• Selected different mics CMA-4544PF Electret
• Condenser Mic from CUI Inc.
• Better sensitivity (-44 dB/-2 dB)
• Better Voltage Rating (3-10 V)
• Wider frequency response (20 Hz- 20kHz)
• Easier form factor to work with
• Previous mics needed PCBs
• These plug right into breadboard
• Faster, easier, better specs
• Also Omni-Directional

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Deliverable Mics into A/D

• Hook up 2 microphones
• Have those feed into A/D
• Show that 2 microphone inputs can be recovered on
  the computer
• DEMO

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Software

• Custom real-time software
• Microsoft Windows application
• Built in C
• Using open source Aquila DSP library to do DSP
  calculations
• Investigating whether we want a matrix math
  library as well
• Currently using Microsoft Windows API to play
  back sound
• Could also use open source API (CoreAudio) to
  play back sound so that the code is platform
  agnostic

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Deliverable Software

• Get overall framework together
• Start hooking up pieces by showing we can load a
  WAV file
• and play it back
• Exercises playback code
• DEMO

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Deliverable MATLAB Simulations

• Taking 2 inputs into MATLAB and beamforming
• Used 2 computer mics to record test signals

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Individual Microphone Inputs
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Sum of Microphone Inputs
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Sum of Delayed Mic Inputs
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Unfiltered DFT of Inputs
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Filtered DFT of Inputs
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Cost Analysis

• Items Purchased So Far
• Remaining to purchase PCBs

Item Purchased Num. Purchased Unit Price Total Cost
A-gtD Converter 1 165 165.00
MEMS Mics 3 3 9.12
Electret Mics 12 .75 14.20
Spent So Far 188.32
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CDR Deliverables

• Nick
• Optimize microphone amplifiers
• Increase to 8 microphone input channels to A/D
• Rebecca
• Take A/D as input into software
• Save out wave file
• Jimmy
• Design Band Pass Filter
• Spherical Wave Algorithm
• John
• Spherical Wave Calculations
• Team
• End-to-End System (take input from multiple mics,
  pass through A/D to computer, perform beamforming
  functions on inputs)

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FPR Deliverables

• Nick
• PCB Fabrication for Amplifiers/Microphone
  Combinations for all 8 inputs
• Rebecca
• Implement scanning, Final Real-Time Analysis
• Jimmy
• Scanning algorithm in MATLAB, Widen frequency
  Range
• John
• Widen frequency range (Algorithms)
• Scanning technique algorithms
• Team
• End-to-End system, beamforming performed on 8
  microphone inputs with a polished, professional
  presentation

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Schedule for 2014
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Questions
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Questions
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Microphones

• Analog Device MEMS Microphone
• Omnidirectional
• Analog output
• Frequency range 100 Hz 15 kHz
• Sensitivity -42 dB /- 3 db _at_ 94 dB SPL
• S/N Ratio 62 dB

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Near-Field Beam Widths