Developing a Noise Canceling Device for Ranged Sound Suppression

Abstract

The purpose of our project was to develop and test a device that was intended to reduce or eliminate noise within an open area. This would be achieved through the use of sound wave interference, by producing the inverse of the sound in order to destructively interfere with the original noise. Our noise canceling device consists of a speaker and microphone built into a small enclosure which was attached to an Arduino, an open-source electronic prototyping platform enabling users to create interactive electronic objects. The Arduino is programmed to analyze the surrounding noise inputted through the microphone before outputting the same noise through the speaker 180 degrees out of phase to achieve destructive interference. Code was developed to obtain the volume of noise before conducting a Fourier transform upon this input to calculate the needed outputted frequency. We hypothesized that the noise canceling device would reduce the noise levels within a defined area, the null hypothesis would then be that no decrease in noise is measured. Our experimentation materials consisted of the noise cancelling device, a sound source, a preset field with consistent distance increments between the device and source, and a decibel meter which measures the sound’s volume. Testing was done by placing the device between the noise source - where a smartphone was used to generate three notes, (G4 (392 hertz), A4 (440 hertz), and B4 (494 hertz)) - and the target area where the decibel meter recorded volume levels. Data from the experiment was consisted of the volume levels in the target after a control test was taken so that the ambient volume of the testing environment was taken into consideration. The data from the testing was averaged out and the results are as follows: The two lower notes, G4 and A4, revealed a decrease in volume from 67.8 dB to 64.3dB and 66.8 dB to 63.7 dB respectively, while the highest note B4 had a slight increase in volume from 67.8 dB to 68.0 dB. Using a t-test to conduct data analysis, the volume change for notes G4 and A4 were found to be statistically significant, rejecting the null hypothesis. The note B4 on the other hand did not have a statistically significant decrease, thus accepting the null hypothesis. By analyzing the results, we concluded that the device performed better at lower frequencies than higher frequencies. This may be influenced by the testing environment, where higher frequency noises are more susceptible to interference, affecting the device’s ability to reduce the noise. Furthermore, the irregularity could be due to higher frequency noises having shorter wavelengths which are harder to position out phase with. Overall, the device did accomplish our project’s goal of reducing low to medium pitched noise within an area, with future goals to extend the device’s effectiveness to higher pitched noises.