Creating a Noise-Cancelling System to Reduce Whale Beaching Events Caused by Ship Noise

Undergraduate #431
Discipline: Technology and Engineering
Subcategory: Civil/Mechanical/Manufacturing Engineering
Session: 2
Room: Exhibit Hall A

Jennifer Chinen - Kapiolani Community College

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Whales are known to beach themselves when they are sick or injured. Current research has shown that there has been an increase in whale beaching events caused by man-made noise pollution. Most of the ocean’s ambient noise is caused by large cargo ships, which produce a predominantly low frequency noise (<1000Hz). Unfortunately, this interferes with the frequency range used by many whale species to communicate and echolocate. Because water is more dense than air, sound travels faster and farther, making the sound much more significant in water. My research objective is to create a functioning noise-dampening system prototype using active noise control/noise-cancellation to mitigate ship noise. To mitigate ship noise, audio recordings of whales and ships first need to be analyzed. Code was written in Matlab to convert these recordings into spectrograms, where the frequencies of sounds could be visually displayed as a function of time. An inverting operational amplifier (op-amp) circuit was then built to reduce ship noise through active noise control/noise-cancellation. Two speakers and a microphone were used to test the circuit on sound waves, with air being the first medium. Several different audio recordings were taken to measure noise before and after going through the inverting op-amp. The audio spectrum analysis showed that low frequency ship noise interferes with the frequency ranges whales use to communicate and echolocate. Audio recordings showed that noise travelling through air was reduced by producing a second inverted sound, resulting in destructive interference. These results indicate that ship noise interferes with whale communication, but can be mitigated through the use of active noise control/noise-cancellation. For future research, the results of this experiment will be applied to our second medium which is water. Waterproofing a noise-dampening system prototype will be done for in-field deployment, which will then be tested and improved to increase its effectiveness in ship noise reduction. References: “Shipping Noise.” Ocean Conservation Research, 22 Apr. 2019, ocr.org/sounds/shipping-noise/?portfolioCats=200%2C201. “ALOHA Cabled Observatory.” ALOHA Cabled Observatory, 15 July 2019, aco-ssds.soest.hawaii.edu/. Southall, B. L., Scholik‐Schlomer, A. R., Hatch, L. , Bergmann, T. , Jasny, M. , Metcalf, K. , Weilgart, L. and Wright, A. J. (2017). Underwater Noise from Large Commercial Ships—International Collaboration for Noise Reduction. In Encyclopedia of Maritime and Offshore Engineering (eds J. Carlton, P. Jukes and Y. S. Choo). doi:10.1002/9781118476406.emoe056

Funder Acknowledgement(s): I would like to thank PEEC II: Pre-Engineering Education Collaborative.

Faculty Advisor: Aaron Hanai, hanaia@hawaii.edu

Role: Everything