Click detection

In phonetics, click detection is a burst of noise that is introduced into one ear while the subject is listening to speech in the other ear.

Comments
The subject has to push a button when he detects the click. By varying the position of the click in relation to the structure of the speech (e.g. grammatical structure, syllabic structure), information is gained about the way in which units are perceived and organised in the brain.

Link
Utrecht Lexicon of Linguistics