An in situ transfer function technique for the assessment of the acoustic absorption of materials in buildings

A method for measuring the absorption properties of materials in situ at mi d to high frequencies is proposed. It is an adapted version of the well kno wn free-field two-microphone transfer function technique to in situ conditi ons. The novel features of the method are presented: noise-immune acquisiti on technique, proper time windowing - both windowing strategy and window ch oice - practical geometrical transducer setup at oblique incidence. A rigor ous study of measurement conditioning as a function of incidence is given u sing the conformal mapping technique. Experimental results are ultimately p rovided in realistic in situ conditions showing the viability of the method with comparison to standing wave tube measurements. (C) 2001 Elsevier Scie nce Ltd. All rights reserved.