Delayed Auditory Feedback

  • Introduction
  • Video & Results
  • Materials
  • Procedure
  • Preparation & Notes
  • Download Files


In this activity, students will:

  1. Experience the difficulty of speaking when hearing is delayed by 200 milliseconds.
  2. Understand the important role that hearing and the brain's interpretation of hearing has on speaking with fluency.
  3. Learn terms including "dysfluency", "fluency", and "auditory feedback".

DAF: Delayed Auditory Feedback

The study of how the brain interprets signals, including sight and sound, and translates it into behaviour is called Cognitive Science. When we speak, our brain expects to hear our voice and then makes adjustments in volume, pitch and clarity. Have you noticed how difficult it is to speak if you cannot hear your voice? Put on headphones that muffle your voice and try to speak naturally. When the feedback of voice to the brain is delayed by a few hundred milliseconds, the brain has difficulty interpreting the signal, (ie. the voice). The process of introducing a delay between when we speak and when it is heard is termed delayed auditory feedbadk (DAF). The result is dysfluency. It becomes difficult to talk without delays, stuttering and slurring. Performers who sing the national anthem in stadiums experience a 1-2 second delay and are advised to wear ear plugs so they are not disturbed by it. Some people are greatly affected by the delay while others have little difficulty speaking with the listening delay. Try it and see how you do!

None at this time.


  • headphones (Sony MDR-210LP at Target for $8)
  • computer or smart phone (we used an iPhone4)
  • DAF Software (see Notes)
    DAF Assistant ($12.99 application for iPhone)
  • A short sentence for subjects to read or a phrase to recite (ie. list the months of the year).

Real-Time Auditory Feedback vs. Delayed Auditory Feedback

  1. Read a short sentence three times and have someone time how long it takes. If the students are too young to read, have them look at a series of shapes and say the names the shapes in order 3 times.


  1. Have the subject repeat step one with headphones and with DAF assistant set to a 200 ms delay. Record this time as well. Is it different?
  2. Repeat step 2, with the same subject but this time allow the subject to look in the mirror while talking.
  3. Record how time of completion of the 3 taks for several people and answer the following questions.

Is delaying audio feedback disturbing to speech in all, many, some or few people?
Do visual cues help overcome the dysfluency?


  1. The use of headphones is important for blocking out the non-delayed feedback of the subject's voice.
    Headphones are regular equipment in elementary schools and hopefully will not need to be purchased.
  2. Turn volume up on the headphones (computer or smart phone) to block the subject from hearing their undelayed voice.
  3. 200 ms delay is optimal for speech disturbance (personal communication with Dr. J.A. Jones).
  4. Software. We used DAF assistant for the iPhone, which cost $12.99. I have seen free software for PC's that can be used but have not tried them. So far, I have not found DAF software for OSX.


  1. Jeffery A. Jones and Danielle Striemer. (2007) Speech disruption during delayed auditory feedback with simultaneous visual feedback. J Acoust Soc Am. 122(4): EL135–EL141.
    doi: 10.1121/1.2772402 (online) (pdf).
Downloadable Files