Used this technique over 40 years ago
While in college during the late 1960s, I was an engineer at a radio station. As a practical joke we would intermittently switch the audio feed to a DJ's headset from live audio to a short delay (created with a tape recorder equipped with separate record and playback heads). The result was normal speech interspersed with periods of stammering gibberish. The DJ could not understand why he could not make the words come out of his mouth. If he would remove his headset, the problem would disappear.