Author: Roselyn Mathew, Reg. CASLPO, Speech-Language Pathologist
Date: Wednesday, September 11, 2024

1. Introduction 

2. Electronic fluency devices and their types 

   • Devices that provide feedback to user regarding their breathing, muscle activity and voice

   • Devices that provide auditory feedback

   • Sound masking device

3. Conclusion 

According to the American Speech- Language- Hearing Association, “fluency refers to continuity, smoothness, rate and effort in speech production. All speakers are disfluent at times. They may hesitate when speaking, use fillers (um, uh), or repeat a word or phrase. These are called typical disfluencies or nonfluencies”. 

Fluency disorder can be defined as “an interruption in the flow of speaking characterized by atypical rate, rhythm and disfluencies (eg. Repetitions of sounds, syllables, words and phrases; sound prolongations and blocks), which may also be accompanied by excessive tension, speaking avoidance, struggle behaviours and secondary mannerisms” (ASHA, 1993).

Electronic fluency devices or fluency devices are tools used for improving fluency. They are divided into 3 categories based on the output that they provide. 

Devices that provide feedback to user regarding their breathing, muscle activity and voice

These devices are computer based and provide information to the user in a computer screen. This information is useful for the user to control their breathing and voice in order to have a smooth flow of speech. This is particularly useful for individuals who are not aware of their disrupted breathing, muscle tension and voice during episodes of dysfluencies. Understanding this would be helpful in controlling behaviours that might lead to increased tension which could result in an increase in dysfluencies.

Examples of devices that provide feedback regarding voice and physiology are Dr. Speech and Electromyography.

In Dr. Speech the user has to read and speak to a mic, where the breathing and the voice qualities of the user are shown in real time. Since immediate feedback is received, the user would be able to modify their voice and breathing for reading and speaking activities. Getting feedback is useful especially when therapy techniques like prolongation and easy onset are used. 

Although there have been studies showing the improved fluency with shorter voice onset, there have not been any substantial studies showing a generalized improvement in fluency by using devices that monitor voice parameters and loudness. 

Electromyography (EMG) is a technique used to measure the muscle activity of a person. It is used for assessing disorders related to muscle and neural dysfunctions. In an EMG test, one or more needles are inserted to the muscle through the skin. These needles are called electrodes. These electrodes give feedback regarding how the muscles respond to electrical stimulations. This feedback is provided as an increase or decrease in the muscle activity and the graph showing them is called an electromyogram. 

For reducing dysfluencies, the electrodes are connected to the muscles in the face and throat. When the person shows a tension on the face or throat during episodes of dysfluencies, they get feedback regarding increased tension of these muscles. This helps them to be aware of the tension and consciously relax, which helps in reducing dysfluencies. 

A 2 to 6 year controlled study done by Hancock et al. concluded that EMG and speech therapy techniques were effective in reducing stuttering, but when EMG and speech therapy techniques were compared, the results showed similar rate of effectiveness in reducing stuttering. 

As needles are inserted into the muscles through the skin, this method is not appealing to individuals who prefer non-invasive techniques. 

Devices that provide auditory feedback

These devices give feedback of the person’s speech by playing it back to them with a delay either in the same way or with an alteration in the frequency. They are of 2 types:

Delayed Auditory Feedback (DAF)

In delayed auditory feedback, the person made to hear their speech as it is. The DAF device picks up the speech and relays it back to the speaker through headphones/earphones with a slight delay. The feedback is mostly given in both ears or to one ear only. The duration of delay can range 50 milliseconds to 200 milliseconds. Initially, in the 1960s and 1980s, the delay of the feedback was kept longer (around 200miliseconds), but since 1990s, the delay has been kept shorter (from 50-100miliseconds), as recent studies have shown that fluent speech is possible without a prolonged speech. 

The idea behind DAF is that when the speaker hears their voice with a delay, they slow down their speaking rate. This slowing down is done mainly by stretching vowels and also by having minute pauses that are not noticeable. Moreover, listening to their own speech continuously with a delay would make them monitor their speech easily. These 2 factors when combined is thought to make the person speak slower as well as intentionally which enhances fluency. 

Frequency- Altered Feedback (FAF)

This device changes the frequency or pitch of the speaker while providing feedback of their voice that is, the speaker hears their own voice in a different pitch. The FAF device picks up speech, alters the pitch and relays it back to the speaker with a slight delay. The feedback is given through headphones or earphones either to both ears or to one ear. The duration of delay of the feedback given is in the range of 50-200 milliseconds. The shift in the frequency is quarter, half or a full octave of the original frequency. This shift in frequency is either made higher or lower than the speaker’s actual pitch. The idea behind change in pitch with delay is to make the speaker to not only slow down and be conscious of their speech, but also to ensure that the delayed auditory feedback does not interfere with their conversation. When the feedback comes with a voice that is different from the speaker, there is less chance of the speaker being unable to focus on the things that they are going to say while having to continue the conversation. FAF is thought to be more beneficial than DAF because of the alteration in voice pitch. 

There are mixed opinions regarding the effectiveness of DAF and FAF. 

A study conducted by Stuart and Kalinowski (1996) has concluded that the use of DAF and FAF devices made people with stuttering have a slower speaking rate which has enhanced fluency.

A systematic review of studies done by Andrade et al. (2011) has concluded that the use of altered auditory feedback devices for the reduction of stuttering do not have robust support for their applicability. 

Although certain studies have shown increased fluency while using DAF and FAF, it is also concluded that using DAF and FAF alone might not be effective in improving fluency. 

The main issue with DAF and FAF is that the speech produced is mostly monotonous and slow, which affects the naturality of speech.

Another issue with DAF and FAF is that the user will have to consistently depend on it for their everyday speech. They will also have to consistently wear earphones or headphones while speaking which is not practical. 

Sound Masking

In sound masking, the person with stuttering is presented with a noise through headphones, to avoid listening to their own speech. The noise that is presented is generally white noise or pink noise. The theory behind using masking is that a lot of people with stuttering report that they do not stutter if they are unable to hear themselves while speaking.  Due to this, it was speculated that one probable cause of stuttering is due to faulty auditory feedback while speaking. Although there is no concrete proof to support this theory, sound masking is done to help the person with stuttering not listen to their own speech, which reduces any faulty feedback that they hear while speaking. Secondly, the noise urges the speaker to increase their volume which helps in reducing their rate of speech. This can reduce dysfluencies. 

A study done by Murray (1969) has concluded that sound masking using white noise helps in reducing stuttering. 

A study done by Garber and Martin shows that the effects of fluency using masking changes over short term and long term masking. Although their test subjects had significantly reduced dysfluencies initially, there were inconsistencies with prolonged masking. 

Sound masking does not help persons with stuttering to monitor their speaking rate or speech in general. 

Some individuals find it impractical to use it during conversations as their ability to hear and understand their conversation partner/s gets affected. 

Moreover, the user will have to constantly depend on the masking noise and wearing headphones/earphones in all speaking situations is inconvenient.

Electronic fluency devices or fluency enhancing devices are devices that are used to reduce stuttering and to improve speaking fluency. Research done regarding these devices have shown mixed results, with some studies supporting an improvement in speech fluency and other studies supporting no change in speech fluency. It is up to the individual to decide about using these devices along with fluency therapy after weighing the pros and cons based on their communication situation and lifestyle.

To speak with a psychotherapist or one of the speech-language pathologists at Well Said: Toronto Speech Therapy, schedule an initial consultation by clicking the link below or calling (647) 795-5277.