This paper describes a method to measure the absorption coefficient of a panel at oblique incidence by a new procedure which combines the Adrienne method (MLS signals with the subtraction technique) with the inverse filter of the electroacoustic system response. This allows to radiate shorter pulses which discriminate better between the different events usually measured in situ (direct, reflected, diffracted, etc.). Therefore, the windows that select the direct and reflected events from the measured trace, which are then used to calculate the absorption coefficient, can be better set up. This in turn optimizes the frequency bandwidth of interest. The method has been validated by applying it to a microperforated panel (MPP) in the anechoic room of the Institute of Acoustics (Madrid). The absorber consists of a (2.44 m × 2.44 m × 1 mm) steel panel properly perforated to provide a suitable absorption bandwidth in front of a wooden panel of (2.44 m × 2.44 m × 2 cm) with an air gap 5 cm wide in between. The inverse filter of the electroacoustic response has been designed so that the radiated pulse has a zero-phase cosine-magnitude spectrum. Experimental absorption curves agree with the predicted ones.
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