Noise Transmission Studies of an Advanced Grid-Stiffened Composite Fairing

Abstract

Interior fairing noise is an important consideration for payload launch survivability and has been studied extensively since the beginning of the space program. This work presents acoustic transmission studies conducted by the Air Force Research Laboratory, Space Vehicles Directorate, on a composite, grid-stiffened, Minotaur payload fairing. These tests were performed in an acoustics laboratory and examined the effects of acoustic flanking paths, the thermal protection system, and melamine-type acoustic blanket treatments on fairing noise. The data showed that acoustic flanking paths significantly increase noise transmission, especially at low frequency. The bare fairing with thermal protection system provided approximately 14 dB of noise reduction over the 5000 Hz bandwidth relative to external levels. Acoustic blanket performance was measured as a function of bandwidth, surface area coverage, and mass. It was observed that small amounts of treatment (2 kg) significantly increased noise reduction (3.6 dB), even at low frequency.

Simple Technique for Precise Measurement of Transmission Loss of Planar Sound Waves

“…Figure 13 illustrates the mode shapes in the resonance vibration of the C/C 2 panel. The same fact is repeatedly true in this case as well; that is, the TL has peaks at resonance modes (3,1) and (5,1), at which there is a peak at the center of the panel. Around the first peak of the TL, the TL curve of the C/C 1 and that of the C/C 2 are occasionally close to each other.…”

“…S OUND transmission through a fuselage panel has been studied widely for aerospace applications [1][2][3][4][5][6]. For example, it is a critical issue to minimize the cabin noise when developing a new aircraft with a quiet and comfortable cabin.…”

“…Acoustic noise from the rocket engines is considered one of the severe problems in launching. A payload inside of a faring may be damaged by the strong vibration and the acoustic noise [5][6][7][8]. The acoustic noise has been reduced by the elaborate designs of the fuselage structure.…”

Experiment and Simulation Analysis on Noise Attenuation of Al/MF Cylindrical Shells

“…However, both mass and volume increase significantly in the abovementioned methods compared to the original acoustic blanket. Lane et al [6] conducted an experiment in composite fairing to study denoising effects of the thermal protection system for MF material under three tested bandwidths but rarely involved denoising rules of MF materials in fairing 2 Shock and Vibration under low and medium frequency. There are relatively fewer researches concerning noise attenuation technologies for sound field in a fairing with acoustic blanket.…”

“…Among common porous materials, MF material shows advantages of lightness, high flexibility, and high acoustical absorption coefficient for medium and high frequencies [8,9] and is applied by US AFRL in design of noise attenuation in composite fairings [6] and is taken by NASA Glenn Research Center as one of the optional noise attenuation technologies for future large carrier rockets [10]. There are a few Chinese researches on in-cavity noise attenuation performance of MF.…”