Ana Bella Gabrielian
(Advisor: Prof. Dimitri Mavris]

will defend a master’s thesis entitled,

Capturing the Acoustic Properties of Small Unmanned Aerial System Noise with a Novel Frequency Weighting

On

Wednesday, July 7th at 1:00 PM EDT
Virtual
https://bluejeans.com/534099673/6068

Abstract
As the advent of Urban Air Mobility (UAM) draws near, the obstacles to such vehicles and operations grow larger. One of these obstacles is the noise created through the operation of these air vehicles. Noise is a public concern as excessive exposure has been shown to contribute to lack of sleep, lack of cognitive abilities in children, and decline in overall cardiac health. There is extensive noise policy for traditional aircraft; however, no noise policy exists for vehicles in the category of UAM. In this thesis, the understanding of small Unmanned Aerial System (sUAS) noise is detailed by investigating the competence of current metrics to describe the annoyance that is created by such vehicles. With regulatory entities such as the Federal Aviation Administration (FAA) forecasting the viability of last mile delivery by sUASs by 2030, it is imperative that acoustical understanding is developed in parallel with this emerging technology. As a part of a NASA research effort, the Design Environment for Novel Vertical Lift Vehicles (DELIVER), a psychoacoustic test on sUASs was conducted to measure human annoyance toward these vehicles in comparison to current delivery vehicles. The study had two main findings: at the same decibel level, test subjects found sUASs more annoying than they did delivery vehicles and the correlation between annoyance and decibel level using four different noise metrics was relatively low. In a preliminary comparison of spectral content between a helicopter and one of the sUASs in this study, it is shown that the sUAS’s spectral content has more tones in the region of frequencies in which humans are especially sensitive. To account for human sensitivity to these tones, the hypothesis is posed: A new frequency weighting, which allows Sound Exposure Level to better correlate with human annoyance caused by an sUAS noise event, will create a larger SEL contour area that is more indicative of sUAS noise. In the first phase of the approach, this hypothesis was tested by creating a design of experiments of different frequency weightings to find a new weighting with a higher correlation coefficient. The resulting frequency weighting (the X-weighting) increased the R2 value from 0.784 to 0.853.  In the second phase, Sound Exposure Level contours were created using the new frequency weighting and current frequency weightings in ANOPP2. The SEL 65 dB contour experienced a 79%, 18%, and 78% increase in length, width, and area respectively between then X- and the A-weighting for one of the sUASs investigated. This methodology grants stakeholders such as regulators and original equipment manufacturers a process to assess frequency weightings and their efficacy in capturing human annoyance; in doing so, this could enable all sUAS stakeholders to create a common “language” with which to discuss the noise created by these vehicles effectively.

Committee

• Prof. Dimitri Mavris – School of Aerospace Engineering (advisor)
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• Mr. Gregory Busch – Genesis Air Mobility
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• Dr. Aharon Karon – Georgia Tech Research Institute
•