In recent years there has been a growing concern about the adequacy of the present American reference for normal hearing of pure tones. Results of earlier studies indicate that survey data tend to confirm the present zero reference, but data from laboratory studies have provided some basis for the contention that the present reference is too high. The purpose of the present study was to provide more definitive data on the threshold of hearing for pure tones through an extended laboratory investigation. Audiometric measurements were made on three groups of subjects ranging in age from 18 to 24 years inclusive. All subjects were otologically normal and showed a life history of minimal exposure to high intensity noise. Two groups were tested with ANB‐HIA earphones and a 5‐db step testing procedure in the method of limits; the other group was tested with Permoflux PDR‐8 earphones and a 2‐db step testing procedure. The results of the study indicate significant differences between the groups tested with the two types of earphones, as well as between male and female subjects. In general, excellent agreement was found with other laboratory studies. The threshold curves of the present study expressed in terms of coupler pressures are offered for consideration as a proposed laboratory standard for normal hearing.