Acoustic Emissions from F-35 Aircraft during Ground Run-Up

Abstract

A multi-organizational effort led by the Air Force Research Laboratory conducted acoustic emissions measurements on the F-35A and F-35B aircraft at Edwards Air Force Base, California in September 2013. These measurements followed American National Standards Institute/Acoustical Society of America S12.75-2012 to collect noise data to support community noise modeling and ground personnel noise exposure assessments. This field study utilized the most spatially extensive measurements of a military jet aircraft to date. In total, the microphone array was composed of 235 unique locations. These locations ranged from radial distances of 3 m outside the shear layer to 1,220 m from the aircraft with angular positions ranging from 0° (aircraft nose) to 160° (edge of the exhaust flow field). The acoustic emissions of the F-35 are presented for engine powers from idle to full augmented power (maximum afterburner). The acoustic emissions are characterized with spatial maps and are discussed in terms of overall and spectral band levels as well as statistical skewness measures. The directivity of the F-35 is described in general and in terms of variations in radial distances and individual spectral bands. Additionally, nonlinear propagation effects are identified and described along the peak radiation region for the range of engine powers.

Dependence of High-performance Military Aircraft Noise on Frequency and Engine Power

“…An extensive measurement of the A and B variants of the F-35 was performed at Edwards Air Force Base in 2013 [10]. They were tied down to a concrete run up pad while the engine was cycled through various engine conditions, from 13% ETR up through 150% ETR.…”

“…A useful coordinate is the jet inlet angle , which is measured from the direction of the jet inlet (− direction) around a microphone array reference point (MARP) which was located at = 7.5 m for the B variant. The array was laid out to the left side of the aircraft as shown in Ref [10], though for ease of plotting and consistency with previous NAH studies, all plots here are mirrored to show it on the right side of the aircraft.…”

“…Over 350 microphones were deployed from the vicinity of the shear layer out to 1200 m from the MARP [10]. This study focuses on a subset of these arrays.…”

“…Ref. [10] states that there is little variation in level between the recorded fields of the A and B variants, so for simplicity this study uses data collected from the B variant that should be sufficiently representative of both.…”

“…Multilobe radiation is a feature of military aircraft jet noise that is seen in several datasets [7,[10][11][12][13][14][15][16][17], though no conclusive explanation of its cause has been given. These lobes are described as either multiple peaks in the spectra at a given measurement location or as multiple local maxima in space across the array when plotting a single frequency.…”