IN the issue of NATURE for July 5 Dr. E. T. Paris discusses some recently published work at the Bureau of Standards on the absorption of sound at oblique angles of incidence. A detailed discussion of Dr. Paris's criticism of our experimental technique does not seem called for at present. These experiments are pioneer work on this subject, and it is much to be desired that others should give the question experimental attention, the more so because the Bureau's results are at variance with previous theoretical conclusions.