Laboratory study of cabin acoustic treatments installed in an aircraft fuselage

The insertion loss of side-wall add-on acoustic treatments was measured using a light aircraft fuselage. The treatments included: no treatment (i.e., baseline fuselage), a production-type double-wall interior, and various amounts of high-density fiberglass added to the baseline fuselage. The source used to simulate propeller noise was a pneumatic-driver with attached exponential horn, supplied with a broadband signal. Data were acquired at the approximate head location for each of the six possible passenger positions. Insertion loss results for the different configurations were analyzed in space-averaged narrowband levels, one-third-octave band levels, and overall levels, and at specific frequencies representing propeller tone spectra. The propeller tone data include not only the space-averaged insertion loss but also the variation of insertion loss of these particular frequencies across the six microphone positions.