Abstract
International reference zero levels for pure-tone audiometers have been recommended by the International Organization of Standardization (ISO) and are under consideration for inclusion in a new American Standard for Audiometers. The new ISO levels are desirable because: (1) the shape of the threshold contour is more accurate, (2) the threshold levels are more readily reproducible, and (3) they will eliminate ambiguity and confusion in the international exchange of audiometric information. The new ISO levels differ significantly from the American Standard values of 1951, but readings on one of these bases can readily be transferred to readings on the other base by a simple arithmetical adjustment.