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Scientific Research
Delayed Adio Feedback for treatment of stuttering by Professor J. van Borsel, Gent University.
For some time it has been known that delayed audio feedback has a beneficial effect and has been used in different stuttering therapies around the world.
In earlier days delayed audio feedback devices were rather large and more intended to be used in a laboratory setting. Nowadays tehre are several much smaller devices on the market that allow patient to use this method in everyday life. At some point a device was developed that looked like a hearing aid.
The fact these smaller devices are more common now means that most likely the role of the logopedist will change in the future. Besides giving regular therapy the logopedist will have to advise the patient about the purchase of delayed audio feedback devices. or patients that want to adress their condition.
The effect of delayed audio feedback outside of a clinical setting and its long term effects has not much been researched untill a test group was setup recently. Nine adult stutterers were surveyed and tested for speech fluency over a period of three months and using a small delayed audio feedback device.
Upon commencing of the experiment speech fluency was measured with and without delayed audio feedback and whilst performing several speech tasks. After this the test subjects were free to use the device for three months and were incouraged to test and experiment with the device under different circumstances. The were required to use the device daily for five mintes of monologue, fifteen minutes of conversation and five minutes of reading out loud. On top of that, they were required to have two telefone conversations with use of the device. The test subjects were often tested if they were actually using the device.
After three months speech fluency was measured again. At the beginning of the experiment the test subjects were significantlly stuttering more without D.A.F. After three months there was no more difference bewteen both conditions. Even without D.A.F. speech had improved significantly. Contrary to some opinions there was no habituation. Even after three months D.A.F. proved effective. Even though stuttering did not completely disappear for some test subjects most were very positive about the effect of the device. Several persons reported that they were no longer afraid to make a call. This is especially important because telefone conversations are some of the hardest things to do for a stutterer.
If even longer use of D.A.F. can result in a even more fluent speech is of yet unclear. Also unclear is how much practice is required to gain a certain effect. All test subjects practised much more then they were required to do. During the exercises test subjects used a audio delay of bewteen 90 tot 150 milliseconds. Other researchers rapported other delayes as optimal. This also requires further testing.
In any case we may conclude that use of a delayed audio feedback device can result in better speech fluency even without minimum supervision by a logopedist. The subjects did report that they found guidance by a logopedist usefull.
One disadvantage is that some of these devices still are too much visible to be used in everyday life. Futher development is underway though.
Prof. J. Van Borsel, Gent University.
D.A.F. Research Results (pdf, 137kb)
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