ACOUSTIC BLANKET PERFORMANCE EVALUATION USING REVERBERATION TIME TEST METHOD

摘要

Boeing Evolved Expendable Launch Systems has developed a new 5-meter payload fairing for its Delta IV launch vehicle. This composite bisector payload fairing represents a design that incorporated new acoustic insulation blanket materials. The new acoustic blanket was selected to provide improvements in acoustic noise reduction and payload protection. Extensive laboratory experiments were performed during the Delta IV launch vehicle qualification test program to quantify noise-reduction characteristic of the fairing acoustic insulation materials. Many laboratory microphones were installed internal and external to the fairing. Reverberation time tests were conducted by installing several loudspeakers within the fairing cavity. Using a broadband random noise generator and audio power amplifier, the loudspeakers were excited and microphone data collected. Microphone data collected were further reduced to sound intensity (1/3-octave band SPL) versus time data. Sound decay curves were generated and reverberation times computed. This paper discusses the test methods, test apparatus, and test article for the reverberation time test.