Auditory presentation and synchronization in Adobe Flash and HTML5/JavaScript web experiments

Substantial recent research has examined the accuracy of presentation durations and response time measurement for visually-presented stimuli in web-based experiments, with a general conclusion that accuracy is acceptable for most kinds of experiment. However, many areas of behavioral research use auditory stimuli instead of, or in addition to, visual stimuli. Much less is known about auditory accuracy using standard web-based testing procedures. We use a millisecond-accurate black box toolkit to measure the actual duration of auditory stimuli, and the synchronization of auditory and visual presentation onsets. We examine the distribution of timings for 100 presentations of auditory and visual stimuli across two computers of difference specs, three commonly used browsers, and code written in Adobe Flash and JavaScript. We also examine different coding options for attempting to synchronize auditory and visual onsets. Overall we find that auditory durations are very consistent, but that lag between visual and auditory onsets varies substantially across browsers and computer systems