1. ENEL 583/589 Electrical, Computer, and Software Engineering In modern society, machinery is frequently used to make our lives simpler, and to help us carry out tasks quickly. Unfortunately, a noticeable inconvenience of machinery is the loud noises they produce. Our goal was to design a computerized active noise control device that will attenuate the noise created by machine engines while keeping the whole system less expensive than conventional silencers. Our design involves the use of a computer to analyze an incoming sound wave and produce a similar sound wave that will interfere with it, cancelling out the noise. In modern society, machinery is frequently used to make our lives simpler, and to help us carry out tasks quickly. Unfortunately, a noticeable inconvenience of machinery is the loud noises they produce. Our goal was to design a computerized active noise control device that will attenuate the noise created by machine engines while keeping the whole system less expensive than conventional silencers. Our design involves the use of a computer to analyze an incoming sound wave and produce a similar sound wave that will interfere with it, cancelling out the noise. Our device was created to meet these specifications: Less than a 3 second response time to match a change in noise frequency. Attenuate the incident waveform by at least 10dB. Attenuate incident waveforms in the frequency range of 100Hz to 1.5kHz. Our device was created to meet these specifications: Less than a 3 second response time to match a change in noise frequency. Attenuate the incident waveform by at least 10dB. Attenuate incident waveforms in the frequency range of 100Hz to 1.5kHz. Design Requirements Why Active Noise Control? Future Goals Figure 1: How Active Noise Control Works Referenced from: www.loqu.com Active noise control works through the use of phase cancellation. This essentially means having the peak of one sound wave meet with the trough of another sound wave. The amplitudes of each wave will add together, and the resultant wave will be lower in amplitude. How does Active Noise Control work? Our device actively cancels out sound by following this process: Measuring sound from the noise source with a microphone. Processing the sound signal and reproducing it with an appropriate phase delay. Measuring the resultant sound wave to confirm if the amplitude is under a specified threshold. If the amplitude is not low enough, the computer cycles through the phase delay time and continuously measures the resultant noise to obtain the optimal noise cancellation. Our device actively cancels out sound by following this process: Measuring sound from the noise source with a microphone. Processing the sound signal and reproducing it with an appropriate phase delay. Measuring the resultant sound wave to confirm if the amplitude is under a specified threshold. If the amplitude is not low enough, the computer cycles through the phase delay time and continuously measures the resultant noise to obtain the optimal noise cancellation. Figure 2: Design Process Diagram Our Design Process Destructive Wave Incident Wave Waves are out of phase Phase delay adjusted as necessary With the creation of our device, we have accomplished a great deal. However there is still much we can achieve. Possible future goals include: Heat shielding the speaker(s) and microphone so the device can work in close proximity to exhaust flows. Transferring the program onto a dedicated sound board to improve response time and decrease the size of the computing device. Designing an interface to allow the user to specify the desired resultant sound level, as well as the range of frequencies which need to be cancelled. With the creation of our device, we have accomplished a great deal. However there is still much we can achieve. Possible future goals include: Heat shielding the speaker(s) and microphone so the device can work in close proximity to exhaust flows. Transferring the program onto a dedicated sound board to improve response time and decrease the size of the computing device. Designing an interface to allow the user to specify the desired resultant sound level, as well as the range of frequencies which need to be cancelled. Signal Flow Figure 3: Signal Flow Diagram