The paper presents a completely new measurement technique for the sound absorption properties of materials, based on the measurements of active intensity and sound energy density. The technique allows one to measure the absorption coefficient with a wide-band excitation, to use frequency bands of any width, and to make measurements both inside a tube or in situ. The intensity technique is compared to the transfer function method (as defined in the ASTM E-1050 Standard) by means of a complete theoretical study and large experimental validation. The results suggest that the new method is at least as accurate and reliable as the ASTM E-1050 Standard. The method also has many advantages: it is faster and easier, it directly produces results in one-third or 1-octave bands, and it can be implemented with portable, low-cost instrumentation.
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