Option 1 using LabChart:Use the digital input to the PowerLab from the secondary computer producing the sound stimulus to the volunteer. Use this signal to generate different preset comments based on one of two different digital inputs, each representing a different tone. Scope View in LabChart can then be set to Comment mode to identify one or the other tone, and average the subsequent EEG signal based on the comment.
Option 2 for LabChart and LabTutor:Rather than using a digital input to the PowerLab to generate a preset Comment, the digital signal from the secondary computer can be sent directly into the analog input on the front of the PowerLab. Providing the voltage offset produced by the secondary computer is sufficient to enable detection by the PowerLab, the customer would then have a channel event to detect (using Cyclic Measurements) and average using Scope View. If a customer has two or more different sounds they wish to separate, they can input the digital input representing each sound into different channels. By repeating the experiment they could then choose which of the channels they use as the event for averaging in Scope View.
Option 3 for LabChart and LabTutor: Another alternative is to split the sound information itself and send this into an analog input/s on the front of the PowerLab. This approach has the advantage of precise timing, as the signal received by the PowerLab will coincide with the signal reaching the subject. One potential disadvantage of this method, however, will be the difficulty (or inability) to distinguish the different sounds in LabChart or LabTutor.