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Date of Award



AAF, DAF, FAF, stutter, fluency


Background and Objectives: Stuttering affects 70 million people worldwide, which is about 1% of the population. Altered auditory feedback (AAF) is a process by which an individual’s auditory speech signal is electronically changed to temporarily increase the fluency of a person who stutters. For the purpose of this systematic review, AAF includes delayed auditory feedback (DAF) and frequency-altered feedback (FAF). This systematic review examines fluency enhancement in adults who stutter when using AAF devices.

Methods: A review of the literature was searched using PubMed, Ovid MEDLINE, PsycINFO, and CINAHL databases with key search terms related to stuttering and AAF. Inclusion criteria included: 1) adults ages ≥ 18 years old who stutter, 2) comparison of altered auditory feedback forms and/or no altered auditory feedback forms in the treatment of stuttering, 3) inclusion of DAF or FAF, 4) outcomes related to aspects of stuttering or people who stutter (e.g., fluency level, speech naturalness, speech rate), and 5) experimental research. Studies were quality assessed and rated by the authors.

Results: A total of 16 articles were included in this review. Articles were of ‘moderate’ quality.

Conclusions: AAF devices are generally effective in reducing stuttering frequency, with most notable fluency enhancement occurring during oral reading. The degree of fluency enhancement between individuals who stutter is variable and is influenced by factors such as stuttering severity. While research generally supports the use of AAF devices in reducing stuttering frequency, there are inconsistent findings regarding speech naturalness. AAF is likely most effective when used in conjunction with traditional speech therapy. Further research is needed to better understand the relationship between AAF and stuttering, particularly regarding unstructured speaking tasks and speech naturalness.


Nancy Gauvin, EdD, CCC-SLP

The Effects of Altered Auditory Feedback (AAF) on Fluency in Adults Who Stutter: A Systematic Review