The determination of absorption characteristics for a given material is developed for in situ measurements. Experiments utilize maximum length sequences and a single microphone. The sound pressure is modeled using the compact source approximation. Emphasis is placed on low frequency resolution which is dependent on both the geometry of the loudspeaker-microphone-sample configuration and the room in which the measurement is performed. Methods used to overcome this limitation are discussed. The concept of the acoustic center is applied in the low frequency region, modifying the calculation of the absorption coefficient.
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