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.

 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 WorksReferenced 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.

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.

Signal Flow

Figure 3: Signal Flow Diagram

Active Noise ControlBy: Greg White, Tyler Mose, Jon Samuelson, Logan Jennyc, Michael Krawczyk

Advisor: Norm Bartly

Sponsor: Noise Solutions Inc.

EE22 Active Noise Control System