In 1939 a symposium was held by the Acoustical Society of America on the measurement of absorption coefficients. In these and other papers, the reverberation chamber method of determining absorption coefficient was analyzed, and explanations for discrepancies between different chambers, and lack of agreement with other methods, were presented in terms of newly developed theory. Since that time, however, practically no progress has been made in the application of this theoretical work. The discrepancies remain unresolved, and the practical problems resulting therefrom have become increasingly serious.
Within recent months, interest in this subject has been strongly reactivated through the attention of three groups, namely, the American Standards Association, the American Society for Testing Materials, and the Acoustical Materials Association. By closely coordinated efforts, these groups are making a new attempt to develop methods of measuring and rating the absorptive properties of acoustical materials which will yield consistent results in the form most useful for practical engineering work and at the same time are grounded in well‐established acoustical theory.
In the present paper, the general problem is outlined from the viewpoint of the acoustical materials manufacturer. Directions of further development in theory and of experimental attacks are suggested.