On the Specification of Zero Hearing Loss

Several dozen young healthy men, aged 17–25 with negative auditory history, were used to determine SPL under a PDR-8 earphone at threshold for each of 8 frequencies. Careful psychophysical techniques were used, and a calibrated sound probe was used to measure SPL. In addition, an audiogram was taken by a common clinical technique. Average SPL of our population differs only a very few db from previous sound probe studies, being 12–20 db fainter than audiometer zero. However, at all but the lower frenquecies, SPL as inferred from the clinical audiogram agreed very well with SPL as measured by sound probe. It seems clear that the audiometer zero does not represent what the normal young ear can do when handicapped by the relative coarseness of clinical practice, as often alleged, but that the original data, on which the audiometer zero is based, contains an appreciable admixture of partial deafness.