Immediate effects of AAF devices on the characteristics of stuttering: A clinical analysis

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Abstract

The present study investigated the immediate effects of altered auditory feedback (AAF) and one Inactive Condition (AAF parameters set to 0) on clinical attributes of stuttering during scripted and spontaneous speech. Two commercially available, portable AAF devices were used to create the combined delayed auditory feedback (DAF) and frequency altered feedback (FAF) effects. Thirty adults, who stutter, aged 18–68 years (M = 36.5; SD = 15.2), participated in this investigation. Each subject produced four sets of 5-min of oral reading, three sets of 5-min monologs as well as 10-min dialogs. These speech samples were analyzed to detect changes in descriptive features of stuttering (frequency, duration, speech/articulatory rate, core behaviors) across the various speech samples and within two SSI-4 (Riley, 2009) based severity ratings. A statistically significant difference was found in the frequency of stuttered syllables (%SS) during both Active Device conditions (p = .000) for all speech samples. The most sizable reductions in %SS occurred within scripted speech. In the analysis of stuttering type, it was found that blocks were reduced significantly (Device A: p = .017; Device B: p = .049). To evaluate the impact on severe and mild stuttering, participants were grouped into two SSI-4 based categories; mild and moderate–severe. During the Inactive Condition those participants within the moderate–severe group (p = .024) showed a statistically significant reduction in overall disfluencies. This result indicates, that active AAF parameters alone may not be the sole cause of a fluency-enhancement when using a technical speech aid.

Educational objectives: The reader will learn and be able to describe: (1) currently available scientific evidence on the use of altered auditory feedback (AAF) during scripted and spontaneous speech, (2) which characteristics of stuttering are impacted by an AAF device (frequency, duration, core behaviors, speech & articulatory rate, stuttering severity), (3) the effects of an Inactive Condition on people who stutter (PWS) falling into two severity groups, and (4) how the examined participants perceived the use of AAF devices.

Highlights

AAF significantly reduced, yet did not eliminate, stuttering during both scripted and spontaneous speech. ► An Inactive Condition also showed a significant improvement of speech fluency for those participants with advanced SSI-4 based severity ratings. ► Blocks were the core behavior most impacted by active AAF parameters. ► While using a device, the most disfluencies remained during spontaneous speech.

Introduction

Altered auditory feedback is considered to be “a collective term for conditions involving the electronic alteration of the speech signal” (Lincoln, Packman, & Onslow, 2006, p. 72). While exposed to the various forms of AAF, speakers perceive their own speech differently from the way they typically hear themselves. In the prominent literature on stuttering numerous forms of technical modifications in one's own voice are portrayed. Among the most thoroughly documented forms of AAF as a clinical tool in the treatment of stuttering are delayed auditory feedback (DAF) and frequency altered feedback (FAF). While exposed to DAF, the speaker will hear himself or herself slightly delayed through headphones, an earpiece, or speakers. The individual delay time in which the speech signal is delivered is measured in milliseconds (ms) and commonly varies between 30 and 500 ms. Although initial studies on DAF utilized long delays of 250 ms and up, more recent studies have focused on shorter delays of up to 75 ms. It was originally concluded that a long delay slows a speaker's speech rate, thus facilitating fluency (Goldiamond, 1965). However, more recent studies have found that increased fluency is maintained even when exposed to shorter delay times, which do not slow a speaker's rate considerably (Natke, 2000, Sparks et al., 2002). The setting of 50 ms delay has been determined to be the “minimum delay necessary for maximum fluency enhancement” (Kalinowski, Stuart, Sark, & Armson, 1996, p. 265). Thus, a 50 ms delay has become a common manufacture recommended calibration for DAF speech aids.

Frequency altered feedback (FAF) is another form of AAF that has been investigated more recently. While experiencing the influence of FAF, a speaker will hear his own voice in either a higher or lower pitch. The impact of this type of aural modification on the speech of people who stutter (PWS) was first documented by Howell, El-Yaniv, and Powell (1987). These authors found significant improvements in the speech fluency of adult stutterers while exposed to FAF. They concluded that FAF is more beneficial in enhancing the fluency of PWS as compared to DAF alone. However, a subsequent study contrasting the effects of DAF and FAF failed to support this assumption (Kalinowski, Armson, Roland-Mieszkowski, Stuart, & Gracco, 1993). Even more inconclusive data on the effect of FAF was published in consecutive studies. While exploring the effect of FAF on scripted speech, Stuart, Frazier, Kalinowski, and Voss (2008) found a reduction in stuttering duration of up to 50%, while Ingham, Moglia, Frank, Ingham, and Cordes (1997) concluded that improvements in fluency during scripted and non-scripted speech were highly variable within their participant group. In further studies on FAF, Natke (2000) reported no significant changes in speech fluency of 12 PWS while reading, but documented improved speech fluency during spontaneous speech (Natke, Grosser, & Kalveram, 2001).

Many of the early investigations on the effects of AAF created the modifications in auditory feedback using intricate systems such as audio mixers, signal processors, microphones and amplifiers in a laboratory setting (e.g. Armson and Stuart, 1998, Howell et al., 1999, Ingham et al., 1997). However, for more than a decade the features of AAF have been available in the form of portable speech aids. As a result, portable devices have been used to deliver DAF and FAF in many of the more recent studies (e.g. Antipova et al., 2008, Bray and James, 2009, Van Borsel and Eeckhout, 2008, Van Borsel et al., 2003). These commercially available AAF devices made it possible to transfer the documented fluency-enhancing effects from scripted speech (Hargrave et al., 1994, Zimmermann et al., 1997) into natural speaking situations. As such, research on speech samples has expanded to include the effects of AAF on spontaneous speech (Armson and Kiefte, 2008, Corey and Cuddapah, 2008, O’Donnell et al., 2008, Lincoln et al., 2010, Pollard et al., 2009).

Since data on non-scripted speech has become available, it appears as though the positive effects of DAF and FAF during oral reading exceed the reported fluency enhancements documented while speaking spontaneously. Therefore, some researchers have expressed doubt that the positive effects reported during scripted speech can be generalized to natural speech (Foundas and Conture, 2009, Ramig et al., 2010). A trend drawn from recently available data is that the responsiveness to AAF appears to vary widely from client to client (Armson et al., 2006, Lincoln et al., 2010, Packman and Meredith, 2011, Pollard et al., 2009). Whether or not a person who stutters will benefit from an AAF device in any given speaking situation is currently not predictable. This may also be due to the fact that little is known about the specific impact of AAF on the clinical features of stuttering. Many studies have looked at alterations in one clinical category, typically frequency of stuttered syllables (%SS), to determine whether or not an individual had benefited from exposure to AAF. For an increased understanding of AAF's fluency enhancing potential, highly individualized aspects of stuttering, such as specific core behaviors and stuttering severity, should be investigated. Lincoln et al. (2010) recognize the role that clinical attributes may play in predicting the benefit of AAF and called for further investigation into the “characteristics that are predictive of responsiveness”.

Attempting to expand recent findings on the effect of AAF on the speech of PWS the current study examines the immediate effect of DAF and FAF. The latter two as well as masking auditory feedback (MAF) have become widely available in the form of prosthetic speech aids. The fluency-enhancing effect of such devices for some PWS has been established by many of the aforementioned studies. However, it remains difficult to predict how different devices impact individual patterns of stuttering in diverse communicative contexts. This study attempts to address this issue by systematically determining the observable changes in fluency associated with AAF. Namely, notable decreases in stuttering were examined more closely by investigating changes among common clinical categories, which can be derived for every PWS. The main objective of this investigation is the evaluation of the devices’ effects on the following dependent variables:

  • 1.

    Stuttering frequency (percent stuttered syllables, %SS) and duration (measured in seconds).

  • 2.

    Speech and articulatory rate (syllables per minute).

  • 3.

    Frequency of three core behaviors (repetitions, prolongations, blocks).

  • 4.

    Stuttering Severity Ratings (SSI-4, Riley, 2009).

Speech characteristics were investigated, within the following scenarios:

  • a.

    Three speech samples: scripted (reading) and spontaneous speech (monolog and dialog) samples.

  • b.

    Four experimental conditions: No Device (no AAF), an Inactive Condition (DAF/FAF settings set to 0), Device A and Device B (using active AAF settings).

In addition to investigating the impact of active AAF settings, delivered by portable speech aids on specific characteristics of stuttering (see dependent variables 1–4), this study also aimed at an evaluation of the impact of active AAF settings itself. For this purpose all participants were exposed to a concealed Inactive Condition setting, during which the participants were under the impression of being exposed to active AAF. In this condition the DAF/FAF settings were disabled (set to 0) in which case the device did not play the user's voice back. Rather participants were exposed to a slight statical contact noise. This setting was applied during the reading sample, as scripted speech has been documented to improve predominantly, when using AAF. The goal was to see whether or not fluency enhancement could be achieved by both the active and inactive AAF settings. A final objective was to interpret the subjective impressions of the client group in terms of the experienced device use.

Section snippets

Participants

A group of 30 PWS (7 females and 23 males) participated in this study. All individuals were at least 18 years of age to be considered for participation. The ages of participants ranged from 18 to 68 years (M = 36.5; SD = 15.2). Participants were all diagnosed with the fluency disorder stuttering with no history of other speech, language or neurological impairments. All participants had received some form of speech and language intervention in the past but none have had any clinical experience with

Effects on stuttering frequency and duration

In order to determine the overall effect each device had on the fluency of the entire participant group (N = 30), changes in frequency and mean duration of the total disfluencies were determined. Total disfluencies include the cumulative stutter-like disfluencies of all three speech samples (reading, monolog, dialog) within three experimental conditions (No Device, Device A, Device B). Refer to Table 1 for a summary of all syllables produced within the No Device and With Device conditions during

Summary of findings and conclusion

The present study attempted to add to the current body of knowledge regarding the immediate effect of AAF on the speech of PWS. Results are based on the evaluation of the impact of two commercially available AAF aids on clinical features of stuttering during both scripted and spontaneous speech.

In agreement with the results of many aforementioned studies, a significant reduction in the occurrence of disfluencies during scripted speech was found. Even though descriptive statistics show

CONTINUING EDUCATION

Immediate effects of AAF devices on the characteristics of stuttering: A clinical analysis

QUESTIONS

  • 1.

    The most thoroughly investigated forms of AAF are:

    • (a)

      Masking and choral reading

    • (b)

      Delayed auditory feedback (DAF) and frequency altered feedback (FAF)

    • (c)

      Choral and metronome speech

    • (d)

      Delayed auditory feedback (DAF) only

  • 2.

    The article expands current knowledge on AAF in the following ways:

    • (a)

      Differentiates between the impact of active AAF settings and an Inactive Condition

    • (b)

      Provides results on the optimal AAF settings

    • (c)

      Directly compares the effects of AAF during scripted and spontaneous speech

    • (d)

      Both a and c

  • 3.

    Results show

Acknowledgments

We wish to thank the device manufacturers of VoiceAmp and Casa Futura Technologies for providing loaned devices for this objective clinical trial, thus supporting the development of an extended evidence-base for AAF. Further we would like to thank the research assistants who have conducted repeated analysis of the speech data. We would also like to express our sincere appreciation for the thoughtful reviews of a draft of this article by Hans-Georg Bosshardt and Paul Blanchet. Last but not

Julia P. Unger, M.A., CCC-SLP, Education: University of Education Heidelberg, Germany, Ph.D. (Speech-Language Pathology), 2009–present; University of Colorado at Boulder, U.S.A., M.A. (Speech & Hearing Sciences), 2006; European Fresenius University of Applied Sciences, Germany/Hogeschool Utrecht, Netherlands, B.S. (Speech-Language Pathology), 2004. Positions held: Founding Clinical Supervisor, Speech & Language Clinic, University of Education Heidelberg; Area of focus: Research, Evaluation &

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  • Cited by (0)

    Julia P. Unger, M.A., CCC-SLP, Education: University of Education Heidelberg, Germany, Ph.D. (Speech-Language Pathology), 2009–present; University of Colorado at Boulder, U.S.A., M.A. (Speech & Hearing Sciences), 2006; European Fresenius University of Applied Sciences, Germany/Hogeschool Utrecht, Netherlands, B.S. (Speech-Language Pathology), 2004. Positions held: Founding Clinical Supervisor, Speech & Language Clinic, University of Education Heidelberg; Area of focus: Research, Evaluation & Treatment of Stuttering; Heidelberg, Germany, 2009–present; Speech-Language Pathologist at the Associated Stuttering Treatment Clinic; Area of focus: Evaluation & Treatment of Stuttering; Boulder, Colorado, U.S.A., 2005–2009. Certificates: BRS-FD Candidate 2010–present; ASHA Certificate of Clinical Competence, 2007.

    Christian W. Glück, Professor, Ph.D., Education: Ludwig-Maximilian University Munich, Germany, Ph.D. (Speech-Language Pathology), 1997; Ludwig-Maximilian University Munich, Germany, M.A. (Speech-Language Pathology), 1992. Positions held: Professor & Chair at the department of Speech-Language-Communication in Special Education, Institute of Special Education, University of Leipzig, Germany, present; Professor at the Department Speech-Language Pathology, School of Special Education at the University of Education, Heidelberg, Germany, 2005–September 2011; Research Assistant & Lecturer at the Department of Speech-Language Pathology and Special Education at the Ludwig-Maximilians University Munich; Area of focus: Assessment of fluency disorders, Munich, Germany, 1995–2005.

    Jürgen Cholewa, Professor, Ph.D., Education: Johann-Wolfgang-Goethe University Frankfurt, Germany, Ph.D. (Speech-Language Pathology), 1995; Friedrich-Wilhelms University Bonn, Germany, M.A. (Clinical Linguistics), 1988. Positions held: Dean of Admissions at the University of Education Heidelberg, Germany, 2003–present; Professor at the School of Special Education, University of Education Heidelberg; Area of focus: Speech science, Evidence-based practice, Heidelberg, Germany, 1998–present; Lecturer & Research Assistant at the Department of Clinical Linguistics at the University of Potsdam; Area of focus: Speech Science, Language Disorders (Aphasia), Academic Development, Potsdam, Germany, 1994–1998.

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