Prototype Continuous-Scan Sound Array

The usage of drones and unmanned aerial vehicles (UAVs) are becoming increasingly common, in both consumer uses for recreation as well as in military applications for surveillance missions. This project focuses on developing a testing apparatus which will be used to quantitively measure the sound generated by small scale autonomous drones. Measuring the level of noise emitted in order to help design laws for residential sectors, and can also help design the future of small UAVs to make minimal noise.

Furthermore, this is the first generation of a continuous scanning sound array, which improves traditional static arrays by decreasing cost and acoustic reflections while increasing resolution of sound measurement.

Current market solutions position an array of microphones in a spherical cloud around the source. This technique vastly limits the resolution of sound intensity measuremed in positional space, creates acoustic reflections due to the necessary supports for each microphone, and is an expensive piece of equipment. Our solution positions these microphones on a circular array which would rotate 360° to sweep out a spherical profile around the source.

The primary functional requirements of this project include:

• Continuous scan arm rotating at 1-3 RPM capable of holding 20-40 microphones

• Analog Output values for microphone positions, with a tolerance of <0.1°, usable for ATA's Data Acquisition System

• Drone frame capable of holding 4 BLDC motors

  • An independent arduino should control these motors via 4 individual ESCs, and should also be capable of measuring and storing sensory data from tachometers

  • Each motor needs to be independently controlled, and integrated with tachometer sensors to determine RPM speed

The group also aims to attain the following reach goals:

• Open loop motor control to track angular velocity of the rotating arc

• Measure force and moments in 3DOF originating from drone, i.e. a force measurement system to measure drone thrust, pitch and roll in real time as a function of propeller speed

• Final Report

• Final Poster

• Final Presentation to ATA

• User Manual

The final design consists of a vertically oriented 40.1” inner diameter array that contains numerous mounting holes for variability in microphone mounting, a camera fixture at the top where the two halves of the array meet, 20-40 microphones and mounts, a drone mockup and related sensors, a drone fixture, shaft, bearing block holding two tapered roller bearings, a gearing mechanism with timing belt, motor, and base tripod for support. Positions for each of the 20-40 microphones are determined by the analysis performed by ATA engineers. The entire project can be divided up into 4 main subassemblies: the rotating array, driving assembly, drone load cell, and wiring & sensors. All dimensions and appropriate CAD files available on the Group’s GrabCAD repository