Bekesy-tracking measures threshold curves by letting the subject reverse intensity direction

Evidence

The frequency dependence of the threshold in quiet can be measured precisely and quickly by Beb§sy-tracking. In this method, the subject uses a switch which changes the direction of the increment or decrement in sound pressure level (see Sect. 1.3). At the same time, but relatively slowly, the frequency is changed from low to high or vice versa, while the subject is changing the sound pressure level of the tone upwards and downwards via the switch according to the following rule: once the tone is definitely audible, a change of the switch reduces the level of the tone towards inaudibility. When the tone becomes definitely inaudible the switch is reversed and the level is increased towards audibility. This process continues throughout the presentation. The decrease and increase of sound pressure level is recorded as a function of time, which, because the frequency is slowly changing, also means as a function of frequency. — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 163