BRRC conducted F-35A/B ground run-up and flyover tests, including pretest coordination, measurements, analysis, and reporting. This project was performed in support of research by the 711th Human Performance Wing’s Battlespace Acoustics Branch, consistent with the goals of WIRTO TO 27, Acoustic Environments and their Impacts on Humans and Structures. Image Credit: F-35 JPO

BRRC, in partnership with BYU,  developed innovative measurement and analysis methods using Near-field Acoustic Holography (NAH) to provide high-quality acoustic data and characterization of the jet-noise source region. The design includes a 150-channel NAH measurement array and data acquisition system, and a state-of-the-art holography processing capability. The prototype system was deployed to perform jet source-noise measurements from an F-22 at Holloman AFB in New Mexico. The culmination of this effort resulted in the ability to show how the scan-based measurements along one plane can be processed using NAH to produce a three-dimensional holographic representation of the sound radiation. This is the first time such a map has been obtained for a full-scale military jet aircraft. Learn more...

As part of an FAA led team, BRRC conducted noise measurements to characterize the noise emissions from Unmanned Aircraft Systems (UAS) during ground and airborne operations for the purposes of UAS noise analysis in support of 14 CRF Part 135. The team accomplished these measurements at Causey Airport in Liberty, North Carolina. The team performed measurement on three UAS vehicles: Flytrex FTX-M600P, Volansi VOLY C10, and DJI m210. The acoustic array included 20 microphones arraigned for flyovers, vertical take and landings, and hover test conditions. Five of the microphones were elevated above the ground up to 30m. The measurements included 172 flyover passes, 95 vertical operations, and 40 hover events. The measurement team included personnel from the FAA, Volpe, and BRRC. FAA coordinated the UAS and flight operations, Volpe led the vehicle tracking data collection, and BRRC led the acoustic data collection.

BRRC conducted a measurement campaign under ACRP Project 02-81 between November 2017 and April 2019 to collect acoustic, operational, and meteorological data during the launches of the Antares 230, Falcon 9, Delta IV Heavy, and Falcon Heavy vehicles. These events represented a range of mission and operation types, including cargo resupply missions to the International Space Station (OA-8E and CRS-15), a research mission (Parker Solar Probe), a communications satellite launch (Arabsat-6A), and first stage return-to-landing operations (Arabsat-6A). Additionally, the measured launch vehicles possess mass-to-orbit capabilities ranging from medium to super-heavy lift designations. In total, over the four measured events, more than 250 acoustic recordings were collected from 70 sites at distances between 0.2 km and 27 km from the launch and landing pads at two distinct spaceports. The acoustic recordings include propulsion noise measurements from all four launch events as well as sonic boom measurements from the return-to-landing operations. The combined acoustic, operational, and meteorological data were analyzed and compiled into a publicly accessible database with thorough supporting documentation. This well-documented, high-fidelity database will equip future researchers with the information necessary to validate current noise models, identify shortcomings, and improve model accuracy by way of better propulsion noise and sonic boom source characterizations.

BRRC was selected by the Agility Prime Program to inspect, process, and analyze the noise data collected from the April 2022 measurements of LIFT’s HEXA aircraft. Four microphones perpendicular to the flight path recorded continuously to capture the noise from three HEXA flyovers for two different payloads. BRRC identified and extracted the ascent, level fly-by, and descent portions of each flyover from each microphone recording using the vehicle’s tracking data. These events were then reviewed for quality and saved using a standard format (ANSI S12.75) which includes pertinent test and equipment information within an ASCII header. For each test condition, event, and microphone, BRRC computed the spectral time history as well as the average sound exposure level (SEL) and average A-weighted maximum sound level (LA,max). These data were delivered in a readable text file format that included the relevant test information. The results of BRRC’s review and analysis were summarized in a slide deck which was presented and delivered to the client. Photo Credit: Samuel King Jr, U.S. Air Force.

Naval Air Systems Command (NAVAIR) Program Management Activity 265 has developed full scale noise reducing chevrons in efforts to reduce the noise produced by General Electric F414 engines in the F/A 18E/F and EA-18G aircraft. BRRC provided oversight and measurement of NAVAIR’s demonstration and validation tests of these F/A-18E jet nozzle chevrons at Naval Air Engineering Station Lakehurst Jet Blast Deflector facility. BRRC measured noise for single-engine and multi-engine static operations and performed a comparative analysis of the chevron effectiveness. Image Credit: US Navy

BRRC assisted the U.S. Army in developing new measurement procedures for characterizing the environmental noise emitted by large weapon systems. The noise software tools, BNoise and RMTK Noise Tool, that DoD uses to predict and assess impacts of large weapon noise require accurate acoustic source emission models. These models require measurements of pressure waveform, peak level, and 1/3-octave-band sound exposure levels. A free-field representation of the sound source acoustical emission, containing no waveform signal perturbations due to the ground, other reflecting surfaces, or propagation anomalies, is required. This research is needed to ensure installation commanders have the best noise information possible to accomplish training and testing with minimum impact on the civilian communities surrounding installations. Image Credit: CERL