Kyle Desrosiers (ME)- Team Lead

Brad Fiedler (EE)

Greg Wodzicki (EE)

Chris VanWagenen (EE)

George Slack- Faculty Guide

P11227- ACTIVE NOISE CANCELLATION

Acknowledgements:Cenco Physics

Texas Instruments

PROJECT DESCRIPTION

• This project aims to attenuate sound level output of a given source using an Active Noise Cancellation system (ANC).

• First of a series of projects ultimately targeting attenuation of Internal Combustion Engine.

KEY CUSTOMER NEEDS

• Prove concept of sound attenuation via Active Cancellation

• Demonstrate technical challenges limitations of ANC

• ANC system fully functional to work on a given input

KEY ENGINEERING SPECS• Noise reduction- Source only vs ANC system on

• Target: >6dB

• Ideal conditions: ~17dB

• Effective Frequency range

• Ideal: 20-20k Hz (Human Auditory Range)

• Actual: 20-1000 Hz

• Processing time

• Ideal: 0.5 ms

• Actual: Unknown

• Speaker Output Level

• ~100dB

CONCEPT SUMMARY

• Sound Waves:

• Propagation of compression and rarefaction through air

Source: http://misclab.umeoce.maine.edu/boss/classes/SMS_491_2003/sound/sound_wave.jpg

SUPER POSITIONING OF WAVES

• In Phase • Out of Phase

SYSTEM ARCHITECTURE

• Microphones: Input Signal, Error Signal• Power Amplifier: Behringer EPQ1200• Speaker: Goldwood GW-210/8

• DSP: • TAS3108EVM2 Eval Kit• C5505 DSP Eval Kit

DESIGN SUMMARY

• System Spec’d for Lawn Mower Engine

• Wye Configuration, Dipole Configuration

• Speakers:

• 10in, 110 Watt RMS

• 86.5 dB Sound Level output

• 40-2200 Hz

• Amp

• 2 x 320 Watts at 8 Ohms

DESIGN SUMMARY

• Microphone

• Typical Frequency Response

• Cheap

• For Initial Testing

• DSP

• TAS3108EVM2 Eval Kit

• C5505 DSP Eval Kit

DSP

• TAS3108EVM2 Eval Kit

• Sampling Rate: 192 kHz

• Programmable in Assembly or GUI Interface

• 8 Inputs/outputs

• C5505 DSP Eval Kit

• Sampling Rate: 48 kHz

• Programmable in C++

• TI Support

• 2 Inputs/Outputs

ALGORITHM

• Least Mean Squares (LMS)

• Modeled in Matlab

• Shown to Work

• Unable to successfully implement in first DSP

• Feedback issues using second DSP stalled implementation

TESTING/RESULTS

• Matlab Simulation

TESTING/RESULTS• Test Setups Conducted

• Straight Inverted Signal, Equal Path Length

• Wye • Dipole Box

TESTING/RESULTS

• 4in Pipe, Wye

TESTING/RESULTS

• 4in Pipe, Dipole

• Lawn Mower Sound Wave• 8dB Reduction

TESTING/RESULTS• 6in, Wye Connection

• Complex Sounds

• Dependent on sound

• Achieved 8dB reduction

TESTING/RESULTS

• Using Microphones and DSP

• Max Reduction achieved: 3dB

• Feedback through mics limited test range

• Testing conducted at low sound levels

SUCCESSES AND FAILURES

• Successes

• Proof of concept

• Geometry, superposition

• Pure tones

• Cancellation of low frequencies with inversion

SUCCESSES AND FAILURES

• Failures

• Programming original DSP

• Programming second DSP, fine tuning

• Microphone Feedback, Clipping

• Unable to implement on non electrical sound source

FUTURE WORK

• Testing

• 6 inch dipole setup

• Back pressure with system in use

• Algorithm debugged

• New microphones

• Eliminate feedback/clipping issue

• System downsized, optimized

• Application to mechanical sound source

SUGGESTIONS

• Computer engineer

• Better knowledge of programming

• Increased budget

• Microphones with proper range, sensitivity, heat properties

• More expert advice/input