Calibration of brief stimuli for the recording of evoked responses from the human auditory pathway

The relationship between the calibration RETSPL-values (reference equivalent threshold sound pressure level) in dB p-p.e.SPL and the corresponding sound pressure levels in dB SPL for brief stimuli is formulated mathematically. The formula is applied on ten brief stimuli consisting of a click, four tone-bursts, a chirp, and four octave-band chirps presented at a stimulus rate of 20 stimuli per second, and using the average acoustical parameter-values from a sample of 20 ER-3A insert earphones in the occluded-ear simulator. The reference calibration values in dB SPL for the ten stimuli are then established. These theoretical values are verified by direct measurements using two different sound-level-meters. It is concluded that the calibration values in dB SPL can be applied in the practical calibration of common brief stimuli. Calibration with these reference values involves only a sound-level meter, and the need for including an oscilloscope in the calibration setup is therefore eliminated.