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Session 2648

HARDWARE AND SOFTWARE PC SKILLS APPLIED TO A SOUND CANCELLATION PROJECT

Sean Daly and Roman Stemprok University of North Texas

Abstract

Developed societies experience an increased level of noise pollution. A Sound Cancellation project was incorporated into a 2 hour-credit Electronics Specials Problems course. The active control of sound is a solution by making an anti-noise for every known noise volume. The anti- noise signal will cancel itself along with the noise. A computer runs an adaptive noise control algorithm in assembly code. The program takes input and determines the corresponding value for a cancellation sound output of analog to digital and digital to analog conversions with sine wave and sound 8-bit I/O.

Introduction

Sound Cancellation is not a new concept in combating noise pollution. Many devices use sound cancellation, but are limited in scope, individual pair of sound cancellation device to each listener. Active Noise Cancellation (ANC) is not a new concept; different consumer products and projects have incorporated noise cancellation. The most successful environments for ANC have been for enclosed spaces such as ducts, vehicle cabins, exhaust pipes, and headphones9. However, most of these products have not yet made the transition into successful commercial products. ANC headphones use destructive interference to cancel low-frequency noise while still allowing the user to hear mid- and high-frequency sounds such as conversations and warning sirens. The headphone system comprises a pair of earmuffs, containing speakers, and one or more small circuit boards. Some headphones include a built-in battery pack, and many allow exterior signal inputs such as music or voice communications9. Another application is active control mufflers for industrial engine exhaust stacks. Active control mufflers have seen years of service on commercial compressors and generators. As unit prices for active automobile mufflers have fallen, several automobile manufacturers are considering active mufflers for future production cars6. Large industrial fans have benefited from active control. Speakers placed around the fan intake or outlet not only reduce low-frequency noise downstream and/or upstream, but they also improve efficiency to such an extent that they pay for themselves within two years. The idea of canceling low-frequency noise inside vehicle cabins has received much attention. Most major aircraft manufacturers are developing such systems, especially for noisy propeller-driven aircraft 9. Speakers in the wall panels can reduce noise generated as the propeller tips pass by the aircraft fuselage. Systems by Noise Cancellation Technologies now comes as standard equipment on the new Saab 2000 and 340B+ aircraft. The key advantage is the savings in weight, active treatments

Proceedings of the 2003 American Society for Engineering Education Annual Conference & Exposition Copyright © 2003, American Society for Engineering Education

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Daly, S., & Stemprok, R. (2003, June), Hardware And Software Pc Skills Applied To A Sound Cancellation Project Paper presented at 2003 Annual Conference, Nashville, Tennessee. 10.18260/1-2--12515