Delayed Auditory Feedback (DAF), also called delayed sidetone, is a type of altered auditory feedback that consists of extending the time between speech and auditory perception. It can consist of a device that enables a user to speak into a microphone and then hear their voice in headphones a fraction of a second later. Some DAF devices are hardware; DAF computer software is also available. Most delays that produce a noticeable effect are between 50-200 milliseconds (ms). DAF usage (with a 175 ms delay) has been shown to induce mental stress. It is a type of altered auditory feedback that—along with frequency-altered feedback and white noise masking—is used to treat stuttering; it has also demonstrated interesting discoveries about the auditory feedback system when used with non-stuttering individuals. It is most effective when used in both ears. Delayed auditory feedback devices are used in speech perception experiments in order to demonstrate the importance of auditory feedback in speech perception as well as in speech production. There are now also different mobile apps available that use DAF in phone calls. Effects in people who stutter Electronic fluency devices use delayed auditory feedback and have been used as a technique to aid with stuttering. Early investigators suggested and have continually been proven correct in assuming that those who stutter had an abnormal speech–auditory feedback loop that was corrected or bypassed while speaking under DAF. In people who stutter with atypical auditory anatomy, DAF improves fluency, but not in those with typical anatomy. DAF is also used with people who clutter. Its effects are slowing of speech which can result in increased fluency for people who clutter and also syllable awareness. Effects in people who do not stutter Studies that are more recent have looked at the effects of DAF in people who do not stutter to see what it can prove about the structure of the auditory and verbal pathways in the brain. Indirect effects of delayed auditory feedback in people who do not stutter include a reduction in the rate of speech, an increase in intensity, and an increase in fundamental frequency that occur to overcome the effects of the feedback. Direct effects include the repetition of syllables, mispronunciations, omissions, and omitted word endings. These direct effects are often referred to as “artificial stuttering." With an individual who does not stutter, auditory feedback speech sounds are directed to the inner ear with