What happens when you alter the speaking environment of a person who stutters? Research shows that making a few changes including - the introduction of noises that prevent the speaker from hearing their own voice and manipulating the sound of their voice before they can hear it - can induce fluency.

Over the years, several types of speech manipulations have been introduced including –

  • Introduction of a slight delay between speaking and hearing
  • Shifting the frequency (up or down) of the voice of the speaker

Both the delayed auditory feedback stuttering therapy techniques work towards inducing fluency in a majority of speakers who stutter. Interestingly, the two techniques mentioned above work for children, teenagers and adults.

How Does DAF Work?

Currently, both prosthetic devices that induce a delay of a few microseconds and state-of-the-art smartphone apps such as Stamurai can produce similar outcomes in inducing fluency in people who stutter.

Delayed auditory feedback (DAF) devices and software work on the principle of choral effect. They introduce a delay between speech production and auditory perception. The delay can be typically customized to be between 50 and 70 milliseconds.

Researchers have observed that a delay of 50 to 70 milliseconds can reduce stuttering by around 70%.

Using DAF to reduce speech disfluency doesn’t require any previous training and conscious effort. It doesn’t lead to abnormal sounding speech. Speakers can maintain a normal speech rate while using a DAF hardware or software to reduce their stutters.

Is DAF Stuttering Therapy Effective in Reducing Stuttering Permanently?

One of the most common questions experts hear from people who stutter (PWS) is “can DAF cure stuttering?” The results of using DAF can vary depending upon the guidance the user receives while they use the DAF device or software (app), and the nature of their auditory processing.

Speech experts now use DAF to improve fluency especially by slowing the speaker’s speech rate up to ten times. Initially, the delay between speech and auditory perception can be 200 milliseconds.

For best results, anyone who stutters should work with a speech pathologist with the goal of shaping their speech for higher fluency. A trained speech language pathologist may gradually reduce the delay from 200 milliseconds to 50 milliseconds.

Alternatively, people who stutter can use Stamurai - a cutting edge speech therapy (with DAF) - for guided stuttering speech therapy and exercises.

The ultimate goals of guided DAF therapy for stuttering is to increase the stress the PWS feels during speaking and to reduce their dependence on the device at the same time.

Multiple studies show that DAF reduces stuttering by 70% almost immediately. A combined approach that uses DAF and FAF (frequency altered feedback) reduces stuttering by around 80%. A combinatorial approach rarely reduces anyone’s stutter beyond 90% or less than 50%.

Using DAF in conjunction with other conventional stuttering therapies can reduce stuttering relapse rates, increase the fluency and hasten positive outcomes in adult clients.

What is a DAF Device?

A user can access DAF technology in the form of hardware or software. A hardware could be a portable altered auditory feedback device that introduces the necessary delay to induce fluency.

Currently, there are two main types of DAF devices available in the market –

  • A single-component DAF device – it looks and fits similar to a hearing aid.
  • A multi-component DAF device – it consists of an earphone and a box (similar to old-school hearing aids). The connection between the box and earphone might be wireless. A wireless device makes its presence less prominent akin to a single-component DAF device.

A few manufacturers offer try-before-you-buy options for the users. If you have never tried a DAF anti-stuttering device in therapy before, you should go for a trial run before investing.

Opting for smartphone-based software that offers DAF through Bluetooth or wired headphones is also a good option for the novice users.

Can A Mobile App Provide DAF Stuttering Therapy?

A smartphone app can provide DAF services. However, the user needs to be cautious that they have access to a verified speech therapist who can guide them properly. Integration of a DAF stuttering app with conventional stuttering therapy can improve speech fluency at a faster rate.

Depending on the DAF mobile app you are using, you may have access to multiple features. Some of these features may include –

  1. Recording the user’s voice – you can record your voice while using DAF and play it back for yourself to hear how much your speech has improved.
  2. Use it regularly – most Pro apps have a “running in the background” feature that allows the user to constantly use the app while conversing, presenting and attending meetings. Many apps offer pro/paid versions that work even when you lock the phone screen.
  3. Measuring speech rate – several iOS and Android apps have a speech rate indicator. The aim of DAF for stuttering is to reduce the speech rate so the user’s speech is comparatively relaxed and clearer. A DAF app with this feature will notify the user if they speak too fast.
  4. Training sessions – although there is no learning curve for using a DAF device successfully, you may want to use a training session or two before using your DAF app during an important meeting or career-defining presentation.
  5. Speech exercises – not all DAF apps have speech exercises. You should look for the ones that do. Exercises will help you apply the speech techniques you learn during stuttering therapy, and give you the chance to couple them with DAF to induce higher levels of fluency.

How to Use DAF for Stuttering?

DAF is an effective assistive technology for stuttering even when it is the only one someone who stutters employs outside a therapeutic environment.

PWS can opt for DAF devices or smartphone apps. If you are using a smartphone app, you will need to install the app and couple a Bluetooth headphone or a wired headset to your phone.

DAF works best under the guidance of a professional and experienced speech therapist or an app that serves a similar purpose. Someone who has the expertise in DAF devices and DAF mobile apps can help PWS to enhance their fluency.

Speech therapists typically recommend a slow-speaking test to determine the progress. Any DAF device works perfectly when the user masters slow-speaking.

Only an expert therapist can guide the user based on their improvements in fluency. With constant guidance the user should be able to reduce the delay from 200 milliseconds to 75 milliseconds and ultimately decrease their dependence on the DAF device.

Common Mistakes People Make While Using DAF To Reduce Their Stutters

For the best results of DAF, you can couple it with speech therapy. While you can approach a speech-language pathologist, you can also follow exercises and receive guidance from speech therapy apps like Stamurai.

Wholesome speech therapy apps can tell you how to use DAF correctly for achieving speech fluency.

Avoid the following mistakes if you are using DAF for the first time –

  1. Setting a longer delay for higher fluency – if you are using a normal-speaking rate, set the delay between 50 milliseconds and 75 milliseconds. Setting it to a longer delay will make the auditory processing worse in those with existing atypical auditory processing.
  2. Expecting speech fluency to increase exponentially – PWS often experience 50% fluency at a delay of 50 milliseconds. They also experience close to 75% fluency at a 75 millisecond delay. However, it does not mean that increasing the delay will also increase your speech fluency.
  3. Not speaking at a slower rate – working with a therapist can help you achieve a slower rate of speaking. Once you have achieved five to ten times slower speaking rate, you can set the DAF delay to 200 milliseconds.
  4. Using DAF only in low stress situations – don’t use DAF in just low stress situations like reading aloud or taking in front of a mirror. You need to test your DAF induced fluency in high-octane situations like in a meeting, during public speaking or live presentations.

Notable Research Findings on DAF and Stuttering

Since stuttering is a heterogeneous disorder not everyone responds to DAF therapy the same way. For example, the Charles A Dana Foundation reported in a NIH study that they had found two sub-groups of PWS – one with atypical auditory anatomy and the other with typical auditory anatomy.

DAF was only helpful in inducing fluency in people with atypical rightward planum temporale asymmetry (auditory anatomy). The other group didn’t become fluent with DAF therapy.

Will DAF Work for Me?

The only way to find out if DAF will work to enhance your fluency during speech therapy is by trying it.

You can either seek help from a SLP or you can rely on a verified speech therapy app like Stamurai to help you out. Using it at the right time in the correct manner makes all the difference.

You need to find the delay that suits your speech rate at the moment. You can use Stamurai to make a list of your feared words and find out how fast you speak. Both of these factors will help you improve your fluency while using DAF for stuttering therapy.