A Probe Tube Method for the Transfer of Threshold Standards between Audiometer Earphones

Abstract

To establish threshold standards for various types of earphones, from a set of threshold standards that has been detd. for 1 particular type of earphone by a hearing survey, an empirical relationship must be found giving the sound pressures in the calibrating coupler corresponding to equal sound pressures in the ear. This was previously accomplished by means of loudness- balancing between earphones. The method descr. in this paper makes use of a direct probe measurement of the sound pressure developed by an earphone at the entrance to the ear canal. The exptl. process is descr., and the results of tests to establish the equivalence of the probe method and loudness-balancing are given. In addition, several of the conditions under which loudness balancing is carried out were investigated by the probe method. Equal loudness sensation was found to correspond to equal sound pressures at the ear, within the limits of exptl. error.