QuietCom Noise-Cancelling Communication System Final Report EE198B-Senior Design II Senior Project Advisor Dr. Raymond Kwok Team Members Gregory Mckernan Sergio Delallana Kevin Chan Kevin Huang May 10, 20082 Table of Contents 1 Introduction……………………………………………………………………....3 1.1 Abstract……………………………………………………………………….…3 1.2 Executive Summary……………………………………………………………..3 2 Design Phase……………………………………………………………………...4 2.1 Design Description………………………………………………………............4 2.2 Design Details…………………………………………………………………...5 2.2.1 Microphone Input……………………………………………………………5 2.2.2 DC Filter…………………………………………………………………….5 2.2.3 Preamplifier………………………………………………………………….6 2.2.4 Unity Gain Phase Inverter…………………………………………………...7 2.2.5 Inverting Amplifier Gain Control…………………………………………...8 2.2.6 Speaker Output………………………………………………………………8 2.3 Noise Cancellation Circuit Layout (PSPICE)…………………………………..9 3 Communications System……………………………………………………….10 3.1 Design ……………………………………………………………………….10 3.2 Communication System Breadboard Implementation……………………….11 3.3 Future Considerations………………………………………………………..13 4 Implementation Phase………………………………………………………….14 4.1 Considerations………………………………………………………………..14 4.2 Different Input/Output device attempts……………………………………...14 4.3 Breadboard Implementation………………………………………………….14 5 Testing Phase……………………………………………………………………15 5.1 Testing Requirements……………………………………………………......15 5.2 Lab Testing…………………………………………………………………..16 5.3 Real-Time Testing…………………………………………………………...16 6 Resources and Costs……………………………………………………………18 6.1 Resources……………………………………………………………….……18 6.2 Costs……………………………………………………………………….....19 7 Conclusion………………………………………………………………………20 8 Team Members…………………………………………………………….…...21 9 Appendix A – Device Specifications…………………………………………...21 10 Appendix B – Figures, Pictures, Tables…………………………………….…21 11 Appendix C – Bibliography……………………………………………………223 1 Introduction This section will introduce the purpose of our project and explain to our intended audience the significance of using the combination of passive noise reduction ear plugs with an active noise reduction system. Our intention is to minimize loud noise and ambient noise. Loud noise is experienced when riding in a fast-moving car or motorcycle. Loud ambient noise can also be experienced when operators are working in data centers with hundreds of servers running, construction sites, or working in clean rooms. Designing an active noise reduction system can certainly make working more comfortable in such areas and help prevent any additional hearing loss. Furthermore, since communication is frequently required in loud areas, we decided to implement communication capabilities into our design. This is so that operators can still comfortably communicate with others. 1.1 Abstract Permanent hearing loss is an inherent problem in many occupations. By adding an active noise reduction system to passive noise reduction earphones, wind noise can be reduced to safer and more comfortable levels. A communication system with noise cancellation will allow operators to function comfortably without sacrificing the ability to communicate with others. 1.2 Executive Summary Permanent hearing loss is serious problem for motorcycle riders. The louder the noise a person is exposed to, the lower the exposure time until permanent hearing loss is sustained. When sound levels exceed 100 dB, maximum safe exposure time is reduced to approximately 2 hours. At 115 dB, safe exposure time is reduced drastically to about 15 minutes (FreeHearingTests.Com). Unfortunately, even with a full face helmet, a motorcycle rider can experience over 115 dB of wind noise at freeway speeds. Currently, passive noise reduction (earplugs), are encouraged for motorcycle riders who expect to ride over 35 mph. However, passive noise reduction will only reduce about 20 dB of noise. We wish to combine active noise reduction with passive noise reduction by adding active noise reducing speakers to earplugs. This small device will be small enough to fit under a motorcycle helmet and when used in conjunction with passive noise reduction - will provide an optimum amount of noise reduction. Furthermore, verbal communication is impossible when exposed to noise levels equivalent to wind noise at freeway speeds. By implementing additional microphones to and a push-to-talk button, operators will be able to hear and speak to those nearby.4 Figure 1. Active Noise Cancellation Combination Active noise cancellation works by combining a sound with the same sound in inverting the phase. In an ideal situation (a perfectly sinusoidal input), the two will add and cancel each other out. 2 Design Phase The most difficult aspect of our communications system is achieving effective noise cancellation. There are two possible approaches in implementing active noise reduction: analog and digital. Due to time constraints and the analog nature of