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Inversion of Helicopter Characteristics Using Infrasound Data

Description: 

Helicopters produce sound across both the audible and infrasonic frequency bands. We are analyzing data from a three-station infrasound network to study the acoustic signals generated by a helicopter during maneuvering within a confined area of approximately 6 km². The helicopter, part of a prescribed burn experiment, operated within this area for almost 2.5 hours, executing multiple closed paths while maintaining two main elevations. The network included 2 two/three-sensor stations and a small aperture six-sensor array. The recorded waveforms show clear tonal noise, with fundamental frequencies slowly drifting between 11 and 15 Hz. The amplitude of the fundamental frequency seemed to increase with decreasing frequency. We are modeling this variability as a Doppler effect, while the amplitude increase is hypothesized to result from a highly anisotropic noise pattern. We are integrating back-azimuth estimations from the sensor array with the temporal evolution of the fundamental frequency recorded across the network to extract details of the helicopter’s operations, such as rotor angular velocity, location, and speed. To validate these inversion results, we are using GPS-based onboard location data from the helicopter. The initial results highlight the potential of acoustic measurements to track and characterize the dynamics of helicopter operations, particularly during complex maneuvering.

Session: Data-driven and Computational Characterization of Non-earthquake Seismoacoustic Sources - I

Type: Oral

Date: 4/16/2025

Presentation Time: 02:45 PM (local time)

Presenting Author: Jonathan

Student Presenter: No

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