Auditory stimulus calibrator

Abstract

The sound intensity control is very important in auditory stimulation because it can modify the electrical brain activity . Fbr that reason, an appropriate acoustic calibration of stimulators for auditory evoked potentials studies is indispensable . The commercial sound cards (Sound Blaster) that are included in the computer multimedia kits are a good stimulator option . Nevertheless, in occasions they don't allow a precise control of the sound intensity. This paper describes the SoundCal board and the Borland Pascal
libraries developed to calibrate the Sound Blaster's audio outputs which are used in auditory stimuli generation . The board is inserted in one of the computer ISA slots and writing and reading operations of its four ports of communication of 8 bits controls it . It also described, the steps of the calibration process, using the SoundCal board and the calibration algorithm . The SoundCal board lets introduce over 80 dB attenuation (1dB steps) in such audio outputs . The developed system can adapt easily to any of the commercial sound board and different earphones . At present time, SoundCal board is being used as a MindTracer complement, which is a stimulator developed at Cuban Neuroscience Center.