M. Smith, M. Heisie*, L.Wolfram†, M. Aebischer†, E. Marasco

University of Calgary, Canada,

*University of Toronto, Canada,†Ecole d’Ingeniers et d’architectes de Fribourg, Switzerland

SSSSH! – Low-cost, Noise Cancelling Solutions for Noise Pollution Issues

in the Urban Home

Ranchland’s Hum and other Urban annoyances

Noise pollution in an urban environment can be problematic.

Obvious problems to solve are

(A) Locating the noise source (B) Negotiating to have it stopped. (C) Helping the home owner cope with the noise pollution until

solutions for (A) and (B) have been found.

This talk is about investigation of whether ‘coping’ can be assisted using a simple noise cancellation approach with a cost of under $500 plus stuff already in a house

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Embedded Systems Courses at University of Calgary

Third year ENCM511 Interfacing with the real world.

Fourth year ENCM515Signal processing issues combined with learning how to write code for ‘real time operation’. REAL TIME means providing results now, and not once we have got back to the office.

Industry sponsored 4th year team design projects

SHARC EVALUATION BOARD

Teaching equipment provided through Analog Devices

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SSSSH! --- SHARC SOUND SUPPRESSION SYSTEM for the HOME

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Key elements Pick up nuisance sound through microphone array

Analyze the nuisance sound

Generate a noise cancellation solution

Use home theatre system as amplifiers to reduce cost Already exists – therefore people likely to try it

Flexible system -- Can also provide Quantitative analysis metrics to support nuisance claims Home tutoring for musicians (Presented at an earlier talk) etc

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Theory – How should it work?

Design of an Electronic Muffler - A DSP Based Capstone Design Projecthttp://www.usna.edu/Users/weapsys/avramov/education/AC_2001Paper214muffler.

PDF

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Theory – How should it work?

WHAT HAPPENS WITH “REAL NOISE SOURCE”

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Investigation configuration

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LAP-TOP AUDIOCITY – AUDIO RECORDINGCUSTOM GUI – STORE ANALYSIS

RESULTS

USE LAP-TOP AUDIO TOBOOST MICROPHONE SIGNAL

SHARC PROVIDESREAL-TIME ANALYSIS

LEDS INDICATE FREQUENCIES PRESENT

CORRECTIVEAUDIO OUT

ANALYSIS RESULTS

AUDIO IN

Problems with ‘distance effects’and ‘extended sources’

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NEIGHBOUR’S ALPHINE HORN

Frequency dependence of the problemWorks for C @ 64 Hz but not C @ 128 Hz

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Lets STOP looking for the perfect solution

Choose a series of useful target situations In the bedroom and generally round-and-about in the house

My Ranchland’s Hum Experience – distant sound source? Low D# (around 40 Hz) – distant refrigerator Annoyance level --- 1 out of 10. Dripping tap in the bath room

However – once noticed would be enough to keep me awake – especially whenever sound characteristics changed

Assume obvious solutions tried Furnace summer fan – white noise source Relocate sleeping location to a ‘null’ in a standing wave?

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SHARC BASED SSSH!

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SHARC ADSP-21469 system Designed as a HOME THEATRE demonstration system

Specialized hardware for high speed DSP (digital signal processing) calculations

Specialized DSP language extensions for high speed real time calculations using C language

Can handle 4 audio input signals Needs help to handle microphones -- home audio system / lap-top

Can generate 8 speaker signals directly Speakers probably inside house unless protecting a community

(from wind farm noise)

Real Life problems to cope with!Are virtual speakers a help or a hindrance?

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Real life distance effects

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CLOSE SPEAKERSPRODUCE

SPHERICAL WAVEFRONTS

This configuration External microphones to capture true noise characteristics

In room speakers

In-room sound microphones to check on compensation

Complicated DSP algorithms probably need to be developed to handle sound reflections, spherical sound waves

Must work for on both sides of the bed

Look for simpler solution that remove all the problems! Multiple microphone ear inserts + earpiece ANC

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Noise reduction system

Active Noise Control

tympanic membrane

ear-canal

ANC-Feedback signal

Noise leaking

This technology under development BUT do we have to wait?

Normal hearing aid Dual micro-phones – single speaker

Problem How do you keep the speaker in place in the ear? Plastic inserts to hold speaker – but which block low frequency sound Compensate by boosting blocked low frequency signals by changing

hearing aid characteristics

Lets play with this idea Completely block all sounds with an ear-mold (essentially ear-plug) Then reintroduce normal sounds using a hearing aid speaker

This is ‘sort of’ already done with ‘electronic hunter’ protection devices –WALKER GAME EARS

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www.walkersgameear.com/wkrs_products/wkrs_bte_dighd_elite_01.html

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Discussion and Conclusion

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Use active sound suppression – GAME EARS or equivalent

Fits directly into ear – blocks Hum but enables normal hearing

Useable in bed or walking around the house

Cheap when compared to high end hearing aids $39 to $500 / $600 compared to $3500 per ear)

Use SSSSH! Embedded system device more for analysis and providing support for claims

Prototype already available

Investigate moving application to cell phones and lap-tops

Where to next?

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Industrial suggested (sponsored) 4 yr Undergraduate Engineering team design project

NSERC (Natural Sciences and Engineering Research Council) Industrial summer student research project Industrial M. Sc. or Ph. D. Scholarships

For more informationemail to SMITHMR @ UCALGARY.CA

Acknowledgements

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Financial support provided through Industrial Collaborative Research and Development grant between NSERC (Canada), Analog Devices (US and Canada), CDL Systems (Calgary, Canada), Ecole d’Ingeniers et d’architectes de Fribourg, Switzerland.

Additional financial support from the University of Calgary.

Richard Patching, Patching Associates, Calgary