Effects of Hearing Protection Device Attenuation on Unmanned Aerial Vehicle (UAV) Audio Signatures

Report No. ARL-TR-7639
Authors: Melissa Bezandry; Adrienne Raglin; John Noble
Date/Pages: March 2016; 20 pages
Abstract: The goals of this study were to investigate the measure of attenuation of hearing protection devices (HPDs) and to develop a filter that uses parameters of HPDs to alter acoustic signatures of Unmanned Aircraft Systems (UASs). The results could be used to select appropriate HPDs for environments where noise from UASs may be distracting. Implemented in Matrix Laboratory (MATLAB), the filter's interface stored several HPDs and their protector factors–Single Number Rating and High-Middle-Low ratings. In custom mode, user-defined HPD parameters were imported into the program. Once a UAS sound file was loaded, the program read it as signal data and displayed graphs of its magnitudes with respect to time and frequency. In the filtering process, the program retrieved the signal's magnitudes and applied different decibel attenuations at certain frequency bands. It then returned the attenuated signal and graphs of its new magnitudes to be compared with the original signal data. The new sounds along with other data displayed in the interface were exported for further study. In the future, the work could aid in the development of a filter to attenuate unmanned aerial vehicle noise in different environmental conditions and to test the effectiveness of HPDs with impulse noise.
Distribution: Approved for public release
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Last Update / Reviewed: March 1, 2016