P17347: Active Noise Cancellation
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Subsystem Build & Test

Table of Contents

Team Vision for Subsystem Level Build & Test Phase

Test Results Summary

Sound test 1 was intended to prove that the physical charateristics of audio cancelling could be achieved. Two speakers where set up directly across from one another, a sound meter was then placed between the speakers. The software generated a pure tone on one speaker, then calculated the phase needed for the other speaker to cancel the first tone at the location of the sound meter. The sound levels where recorded for background levels, just pure tone, and cancelled tone.

Sound Test 1 Setup

Sound Test 1 Setup

The resuls of the tests showed a ~15dB reduction in sound levels once the cancellation tone was emitted.

The the test results. The test results indicate that the phase calculation was unable to accurately generate a phase for asymetric setups.

Test Distance A (in) Distance B (in) Overall Distance (in) Frequency (Hz) Ambient (dB) Tone (dB) Cancelled (dB) Reduction (dB)
2 8 8 16 440 45.7 82.8 72.3 10.5
4 12 12 24 440 47.3 75.9 66.8 9.1
6 12 12 24 200 47.3 69.4 52.3 17.1
8 12 12 24 10000 47.3 82.5 66.3 16.2
9 12 12 24 440 47.3 77.6 68.9 8.7
Frequency Response

Frequency Response

Sound Test 2 was intended to show a programatical means to achieve sound reduction without knowingg the layout of the noise source or cancellation speaker. Two speakers where set up with the computer (acting as the microphone) in between. The code then generated a fixed pure tone on one speaker and a cancellation tone on the other. The phase of the cancellation tone was swept from 0 to 1 (normalized phase). The amplitudes of at the recording device where recorded. The phase that resulted in the lowest amplitude was then selected for an amplitude sweep. The second sweep used a fixed phase and swept the amplitude of the cancellation tone. The amplitude that resulted in the lowest measured amplitude was then recorded.

Sound Test 2 Setup

Sound Test 2 Setup

Phase and Amplitude Sweeps

Phase and Amplitude Sweeps

Amplitude Waveforms Pre and Post Cancelllation

Amplitude Waveforms Pre and Post Cancelllation

Updated Gannt Chart

Updated Gannt Chart

Functional Demo Materials

Initial Test Waveform

Initial Test Waveform

Plans for next phase

Now that we have acquired a workspace in which we can run tests, our plan for next phase consists entirely of building and testing the next steps shown in our Gannt chart. The main 3 phases are:


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