Delayed Auditory Feedback Research Articles

Stuttering inhibition via altered auditory feedback during scripted telephone conversations

Overt stuttering is inhibited by approximately 80% when people who stutter read aloud as they hear an altered form of their speech feedback to them. However, levels of stuttering inhibition vary from 60% to 100% depending on speaking situation and signal presentation. For example, binaural presentations of delayed auditory feedback (DAF) and frequency-altered feedback (FAF) have been shown to reduce stuttering by approximately 57% during scripted telephone conversations. To examine stuttering frequency under monaural auditory feedback with one combination of DAF with FAF (COMBO-2) and two combinations of DAF with FAF (COMBO-4) during scripted telephone conversations. Nine adult participants who stutter called 15 local businesses during scripted telephone conversations; each condition consisted of five randomized telephone calls. Conditions consisted of (1) baseline (i.e. non-altered feedback), (2) COMBO-2 (i.e. 50-ms delay with a half octave spectral shift up), and (3) COMBO-4 (i.e. 200-ms delay and a half octave spectral shift down in addition to the COMBO-2). Participants wore a supra-aural headset with a dynamic condenser microphone while holding a receiver to their contralateral ear when making telephone calls. Stuttering was significantly reduced during both altered auditory feedback (AAF) conditions by approximately 65%. Furthermore, a greater reduction in stuttering was revealed during the COMBO with four effects (74%) as compared with the COMBO with two effects (63%). Results from the current study support prior research reporting decreased stuttering under AAF during scripted telephone conversations. Findings that stuttering was significantly reduced to a greater extent under the COMBO with four effects condition suggest that second signals reduce stuttering along a continuum. Additionally, findings support prior research results of decreased stuttering frequency under AAF during hierarchically difficult speaking situations. Clinical application of these findings may be that people who stutter can use specific software or smartphone applications that produce second speech signals to inhibit stuttering frequency effectively during telephone conversations.

Individual differences in auditory-motor integration revealed by speech fluency manipulations

A role for auditory feedback in maintaining fluency appears less specific than for pitch control, as one example, but delayed auditory feedback (DAF) clearly provides a potent manipulation of fluency. As most speakers are susceptible to DAF, we predicted DAF is particularly suited to identifying individual differences in auditory-motor integration. We conducted a series of studies to probe susceptibility to DAF-induced disfluency in 60 normally fluent speakers during conversation and oral reading. We further contrasted DAF effects on fluency with dual-task effects on fluency. During conversation and reading under DAF (250 ms delay), multivariate cluster classification indicated speakers show high, low, or intermediate susceptibility to disfluency. In contrast, dual-task effects on fluency appeared bimodal with individuals showing high or low susceptibility. DAF susceptibility was not related to dual-task disfluency in 41/60 speakers, but the remaining speakers were disfluent under DAF and dual-task conditions. When the DAF paradigm was extended to adults who stutter, most were classified as highly susceptible. The findings provide compelling evidence that individual differences need to be considered in auditory-motor integration research. Fluency is influenced by both auditory feedback and cognitive factors related to attention, which can inform theories of normal and disordered speech.

Overcoming Stuttering Using Delayed Auditory Feedback (DAF): A Case Study

Background: With the tremendous improvements in technology in producing new techniques to overcome stuttering, many assumptions were stated from different aspects. Aims: To in/validate some of the stuttering assumptions, the present study attempts to investigate the role played by Delayed Auditory Feedback (DAF) device in overcoming stuttering and improving stutterers’ fluency. Methods: A client study of MO, a 23-year old bilingual student who exhibits stuttering and language delay due to psychological factors. An intensive therapeutic treatment which continued for 20 months has been given to the client at hand. The client had to practice (in English) ten(10) alphabetical characters, twenty (20) words (10 nouns and 10 verbs), and ten (10)sentences for four continuous hours every day. Results: The analyses of the client’s utterances throughout five entire sessions show that his rate of speech became slower if not almost normal across increases in DAF. The findings reveal that simultaneous application of both treatments on speaking through DAF was successful in reducing the rate of stuttering in the speech of the client under investigation. It all depends on age, determination, the level of severity, and the way he/she uses DAF. These findings account for the results that support many theories of stuttering including Phonemic Content Theory, Covert Repair Hypothesis (CRH) and Johnson's theory. Taken together, these results weigh strongly against the hypothesis stated that stutterers have generally high levels of emotional reactivity (e.g., Brutten/Shoemaker, 1967).

Effects of delayed auditory and visual feedback on sequence production

This study represents the first systematic comparison of the relative contributions of auditory and visual feedback to sequence production. Participants learned an isochronous melody that they performed on a keyboard and attempted to perform this sequence at a prescribed rate while auditory and visual feedback were manipulated. Delayed auditory feedback (DAF) and delayed visual feedback (DVF) both tended to slow production of the sequence. These effects were additive. There was no modulation of this effect of delay in either modality by the absence of feedback in the other. In contrast with past research, DAF did not increase timing variability, though DVF did. Motion analyses ruled out differences in salience of visual feedback between delayed and non-delayed conditions as an explanation of the effects of DVF. The results suggest that the effects of delayed feedback may be attributable to both sensorimotor interference and to conflicting information across feedback channels.

The effect of portable DAF usage in daily life on the speech intelligibility of dysarthrias

Dysarthria is a neurologic motor speech impairment due to a pathological change of nerve and muscle system. Several rehabilitation methods of speaking rate control have been widely used to improve speech intelligibility for mild dysarthria. Nevertheless, speech intelligibility of the dysarthric patients show almost no improvement outside of a clinic. Delayed auditory feedback(DAF)is one of the speaking rate control methods. Recently a small portable DAF device has been developed, which enables dysarthric patients to use it in their daily life. In this study, wearing a portable DAF, two dysarthric patients conducted a 20-minute practice per day for three months. In the practice, they instructed to prolong vowel length in DAF usage. Intelligibility tests for single-word utterance and for reading aloud a long sentence were conducted before and after the practices. As a result, the single-word intelligibility score increased from 84.0% to 90.6% in case1, and from 68.3% to 89.7% in case2. Additionally, vowel space in the F1-F2 space in case2 enlarged. Both the performance of long sentence reading and free conversation will be presented in the meeting. These results suggest that a portable DAF effectiveness in daily use. This work was supported by JSPS KAKENHI 10424889.

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

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.

Audio-Vocal Monitoring System Revealed by Mu-Rhythm Activity

Understanding the neural mechanisms underlying speech production has a number of potential practical applications. Speech production involves multiple feedback loops. An audio-vocal monitoring system plays an important role in speech production, based on auditory feedback about the speaker’s own voice. Here we investigated the mu-rhythm activity associated with speech production by examining event-related desynchronization and synchronization in conditions of delayed auditory feedback (DAF) and noise feedback (Lombard). In Experiment 1, we confirmed that the mu-rhythms were detectable for a conventional finger-tapping task, and vocalization. In Experiment 2, we examined the mu-rhythms for imagined speech production. We tested whether the same motor-related mu-rhythm activity was exhibited while participants listened to their own voice, and while reading. The mu-rhythms were observed for overt vocalization and covert reading, while listening to simulated auditory feedback of the participants’ own voice reading text. In addition, we found that the mu-rhythm associated with listening was boosted and attenuated under the DAF and Lombard conditions, respectively. This is consistent with the notion that auditory feedback is important for the audio-vocal monitoring system in speech production. This paradigm may help clarify the way in which auditory feedback supports motor planning, as indexed by the motor-related mu-rhythm.

Perceptual calibration to delayed auditory feedback of self-body movement

Temporal contingency between self-body movement and its auditory feedback is crucial to perceive external auditory events. The present study examined whether delay detection of self-generated sound is modulated by short-term exposure of delayed auditory feedback. A total of 36 healthy students participated in Experiment 1 (, age 21.4 ± 1.3 years, mean ± SD) and 2 (, age 20.8 ± 1.4 years). In both experiments, the subject pressed a button with their right index finger and judged whether the auditory feedback (full-range pulsed sound) delivered through a headphone was delayed or not, compared to the sensation of the finger movement. Auditory feedback delay was inserted by using a sound effector device (SPX2000, YAMAHA, Japan). The durations of auditory feedback delay were ranged from 118 to 352 ms at 33.3 ms intervals in Experiment 1, and from 19 to 253 ms in Experiment 2. To calculate the point of subjective equality (PSE), where the delay detection rate was 50%, we have fitted a logistic function to the delay detection probability curve for each subject. The results showed that PSEs were 209.0 and 137.5 ms in Experiment 1 and 2, respectively, which were significantly different (, ). This indicates that PSE was modulated by the range of the delay used in the experiment; PSE became longer as the delay lengthened. We suppose that the perceptual delay in auditory feedback of self-body movement is automatically calibrated to the frequently exposed duration between self-body movement and the auditory feedback.

Immediate speech fluency improvement after application of the Digital Speech Aid in stuttering patients

SummaryBackgroundThe Digital Speech Aid (DSA) is a pocket-sized device used for speech correction in stutterers. The device modifies the patient’s auditory feedback with the use of Delayed Auditory Feedback (DAF) and Frequency-shifted Auditory Feedback (FAF). Both methods are well-known to improve speech fluency in stuttering persons. The aim of this study was to assess immediate disfluency reduction after application of the DSA.Material/MethodsThe study included 335 patients aged 6–64 years with speech disfluency. DSA fitting was performed during 3-day hospitalization. Speech disfluency was assessed during reading, in dialogue and in monologue before fitting and after selection of optimal DAF and FAF parameters. Fluency improvement was assessed statistically with Student’s t test for logarithms of the odds of disfluency presence without the DSA and with the DSA.ResultsFor all speaking situations, statistically significant improvement was achieved, with p<0.005. Immediate fluency improvement was observed in 82.1% of patients during reading, in 84.5% during dialogue, and in 81.2% during monologue. Values different from placebo (reliable improvement) were obtained in 66.9% of patients during reading, in 66.6% during dialogue, and in 63.9% during monologue.ConclusionsThe results show that the DSA is an effective tool for immediate disfluency reduction in stutterers.

Temporal Recalibration in Vocalization Induced by Adaptation of Delayed Auditory Feedback

BackgroundWe ordinarily perceive our voice sound as occurring simultaneously with vocal production, but the sense of simultaneity in vocalization can be easily interrupted by delayed auditory feedback (DAF). DAF causes normal people to have difficulty speaking fluently but helps people with stuttering to improve speech fluency. However, the underlying temporal mechanism for integrating the motor production of voice and the auditory perception of vocal sound remains unclear. In this study, we investigated the temporal tuning mechanism integrating vocal sensory and voice sounds under DAF with an adaptation technique.Methods and FindingsParticipants produced a single voice sound repeatedly with specific delay times of DAF (0, 66, 133 ms) during three minutes to induce ‘Lag Adaptation’. They then judged the simultaneity between motor sensation and vocal sound given feedback. We found that lag adaptation induced a shift in simultaneity responses toward the adapted auditory delays. This indicates that the temporal tuning mechanism in vocalization can be temporally recalibrated after prolonged exposure to delayed vocal sounds. Furthermore, we found that the temporal recalibration in vocalization can be affected by averaging delay times in the adaptation phase.ConclusionsThese findings suggest vocalization is finely tuned by the temporal recalibration mechanism, which acutely monitors the integration of temporal delays between motor sensation and vocal sound.

Adaptation to Delayed Speech Feedback Induces Temporal Recalibration between Vocal Sensory and Auditory Modalities

We ordinarily perceive our voice sound as occurring simultaneously with vocal production, but the sense of simultaneity in vocalization can be easily interrupted by delayed auditory feedback (DAF). DAF causes normal people to have difficulty speaking fluently but helps people with stuttering to improve speech fluency. However, the underlying temporal mechanism for integrating the motor production of voice and the auditory perception of vocal sound remains unclear. In this study, we investigated the temporal tuning mechanism integrating vocal sensory and voice sounds under DAF with an adaptation technique. Participants read some sentences with specific delay times of DAF (0, 30, 75, 120 ms) during three minutes to induce ‘Lag Adaptation’. After the adaptation, they then judged the simultaneity between motor sensation and vocal sound given feedback in producing simple voice but not speech. We found that speech production with lag adaptation induced a shift in simultaneity responses toward the adapted audito...

Delayed auditory feedback and movement.

It is well known that timing of rhythm production is disrupted by delayed auditory feedback (DAF), and that disruption varies with delay length. We tested the hypothesis that disruption depends on the state of the movement trajectory at the onset of DAF. Participants tapped isochronous rhythms at a rate specified by a metronome while hearing DAF (for piano tones) of differing lengths. Motion capture was used to analyze movement trajectories. Mean Inter-Response Intervals (IRIs) varied as an approximately sinusoidal function of feedback condition, with DAF causing slowed production for shorter delays and speeded production for faster delays. Motion capture analyses revealed that finger velocity at the time of DAF predicted the effect of DAF on mean IRI whereas finger position predicted the variability of IRIs. A second experiment in which participants were instructed to vary the timing of peak finger height confirmed that the effect of DAF on timing variability is directly influenced by the finger trajectory.

Análise sistemática da efetividade do uso da alteração do feedback auditivo para a redução da gagueira

To perform a systematic review of studies related to the effects of delayed auditory feedback on speech fluency in individuals who stutter. Concepts of the Cochrane Handbook were followed: formulation of initial question (theme to be reviewed), location and selection of studies (PubMed database) and compatibilization among researchers (aiming to minimize possible citation losses). The following were excluded: citations in languages other than English, citations that did not allow access to full text, repeated citations due to the overlap of keywords, studies developed exclusively with fluent individuals, case reports, reviews of the literature, letters to the editor, and texts that were not directly related to the theme. Hence, texts that were related to treatment with delayed auditory feedback (DAF) and frequency-altered feedback (FAF) were analyzed. Data were analyzed according to research indicators and according to study quality markers. The results indicated that the use of altered auditory feedback devices for the reduction of stuttering events still do not have robust support for their applicability. Methodological variability does not allow a consistent answer, or a trend about the effectiveness of the device, to be drawn. Although the limitations in the studies prevent generalizations about the effectiveness of the device for the reduction of stuttering, these same limitations are important resources for future research planning.

Rhythmic Versus Phonemic Interference in Delayed Auditory Feedback

Delayed auditory feedback (DAF) of a speaker's voice disturbs normal speech production. Various traditional theories assume that the content of the delayed feedback signal interferes with the actual production of a particular speech unit (phonemic content hypothesis). The displaced rhythm hypothesis as an alternative explanation suggests that speech disturbances arise from a disruptive rhythm that is produced by the delayed speech signal. The present experimental study directly contrasted the role of rhythm and speech content in a DAF task using speech units as stimuli. One hundred fifty-one participants read aloud 4 different sequences of double syllables that varied in phonemic content and rhythm while auditory feedback was either nondelayed or delayed by 200 or 400 ms. In line with previous studies, the authors found a peak of disturbances at a delay of about 200 ms, independent of speech rate. More important, the present results clearly support the displaced rhythm hypothesis. A speech rate dependency of this effect was also found. Rhythm seems to be a significant criterion of speech monitoring, and hence a mismatch between spoken words and auditory feedback realized by DAF induces obvious speech problems on rhythmic level regardless of phonemic discrepancy at the same time.

An Experimental Investigation of the Effect of Altered Auditory Feedback on the Conversational Speech of Adults Who Stutter

To investigate the impact on percentage of syllables stuttered of various durations of delayed auditory feedback (DAF), levels of frequency-altered feedback (FAF), and masking auditory feedback (MAF) during conversational speech. Eleven adults who stuttered produced 10-min conversational speech samples during a control condition and under 4 different combinations of DAF, FAF, and MAF. Participants also read aloud in a control condition with DAF and FAF. A statistically significant difference was found between the NAF conversation condition and the 4 combined altered auditory feedback (AAF) conditions. No statistically significant differences in percentage of syllables stuttered were found in conversation or reading between the control conditions and the FAF/DAF or MAF conditions. The analysis of individual participants' data showed highly individual responsiveness to different conditions. Participants' varying responses to differing AAF settings likely accounted for the failure to find group differences between conditions. These results suggest that studies that use standard DAF and FAF settings for all participants are likely to underestimate any AAF effect. It is not yet possible to predict who will benefit from AAF devices in everyday situations and the extent of those benefits.

Brain activation in adults who stutter under delayed auditory feedback: An fMRI study

It is well known that some people who stutter (PWS) show an immediate reduction of stuttering when they speak under a condition of delayed auditory feedback (DAF). In the present study, to investigate cortical activations during speech production through the DAF effect, we performed functional magnetic resonance imaging (fMRI) experiments under the NAF (non-altered feedback) and DAF conditions for PWS and people who do not stutter (PWNS). The results are that (1) the PWS showed the higher activation in the right inferior frontal gyrus (Brodmann Area (BA)45) than the PWNS under the NAF condition; (2) the activations of the right superior temporal gyrus and the right middle temporal gyrus were higher under the DAF condition than the NAF in both PWNS and PWS groups; (3) the PWNS showed the higher activation in the right supplementary motor area and superior temporal gyrus than the PWS under both NAF and DAF conditions; (4) the PWNS showed the higher activation in the inferior frontal gyrus(the right BA45 and the bilateral BA46) under the DAF condition than the NAF. These results reconfirm most of the previous findings with some slightly different activation areas, and underscore the involvement of inferior frontal gyrus and superior temporal gyrus in dysfluency.

Delayed auditory feedback effects during reading and conversation tasks: Gender differences in fluent adults

Delayed auditory feedback (DAF) impacts the speech fluency of normally fluent males more than that of normally fluent females. Understanding this gender difference may contribute to our understanding of gender differences in the prevalence of developmental stuttering. To characterize this gender difference in fluent people, DAF-induced dysfluency was measured in 20 male and 21 female young adults during oral reading and conversation tasks. Stutter-like dysfluencies (SLDs), articulation errors, interjections, reading errors, and speech rate were measured for both speech tasks as the participant spoke without feedback, with non-delayed feedback, and with DAF presented with 5 delay intervals (14 conditions total). DAF induced SLDs (but not other dysfluencies) more frequently during conversation than reading, and this effect was significantly greater for males than females ( Gender × Task × Feedback interaction). Males also produced significantly more reading errors than females. DAF reduced speaking rate significantly more while reading than conversing ( Task × Feedback interaction). DAF significantly decreased the frequency of interjections and increased the frequency of articulation errors; however, no Gender effects on these variables were observed. Although significant order effects indicated improved fluency across trials, covariance analysis suggested that order effects could not explain other results. Educational Objectives: After reading this article, the reader will be able to (1) Discuss developmental stuttering (DS) and gender differences in DS prevalence. (2) Define delayed auditory feedback (DAF). (3) Evaluate the evidence that gender is linked to DAF effects on fluent people. (4) Summarize the results of new research designed to assess sex differences in DAF effects on speech fluency in normally fluent adults. (5) Evaluate the degree to which evidence from the literature indicating that individual differences in attentional control may help us understand gender difference in DAF effects and possibly in DS prevalence as well.

Effects of altered auditory feedback (AAF) on stuttering frequency during monologue speech production

The present study investigated the immediate effects of eight altered auditory feedback (AAF) parameters on stuttering frequency during monologue speech production on two occasions. One of the modern commercially available portable anti-stuttering devices, “The Pocket Speech Lab” (Casa Futura Technologies ®) was used in the study to produce the auditory feedback alterations. Six types of combined delayed auditory feedback (DAF) and frequency shifted auditory feedback (FAF) and two types of DAF alone were tested for eight participants aged 16–55 years, with stuttering severity ranging from mild to severe. The present study found that AAF is an effective means to reduce stuttering frequency during monologue speech production. All eight AAF experimental conditions reduced stuttering frequency, however, there was substantial variability in the stuttering reduction effect across experimental conditions and across participants. There was also instability in stuttering reduction across the two testing sessions. On average, a 75 ms time delay on its own and a combination of the 75 ms time delay and a half octave downward frequency shift were found to be more effective than other combinations of AAF parameters that were investigated. Educational objectives: After reading this paper, the reader should be able to (1) summarize the research investigating the effect of altered auditory feedback on stuttering frequency during monologue speech production; (2) describe the stuttering reduction effect of the eight parameters of AAF tested during monologue speech production; and (3) discuss the possible clinical implications of the use of AAF for stuttering treatment.

The speech naturalness of people who stutter speaking under delayed auditory feedback as perceived by different groups of listeners

This study investigated listeners’ perception of the speech naturalness of people who stutter (PWS) speaking under delayed auditory feedback (DAF) with particular attention for possible listener differences. Three panels of judges consisting of 14 stuttering individuals, 14 speech language pathologists, and 14 naive listeners rated the naturalness of speech samples of stuttering and non-stuttering individuals using a 9-point interval scale. Results clearly indicate that these three groups evaluate naturalness differently. Naive listeners appear to be more severe in their judgements than speech language pathologists and stuttering listeners, and speech language pathologists are apparently more severe than PWS. The three listener groups showed similar trends with respect to the relationship between speech naturalness and speech rate. Results of all three indicated that for PWS, the slower a speaker's rate was, the less natural speech was judged to sound. The three listener groups also showed similar trends with regard to naturalness of the stuttering versus the non-stuttering individuals. All three panels considered the speech of the non-stuttering participants more natural. Educational objectives: The reader will be able to: (1) discuss the speech naturalness of people who stutter speaking under delayed auditory feedback, (2) discuss listener differences about the naturalness of people who stutter speaking under delayed auditory feedback, and (3) discuss the importance of speech rate for the naturalness of speech.

Providing simultaneous visual feedback may ameliorate speech disruptions caused by exposure to delayed auditory feedback

Speakers exposed to delayed auditory feedback (DAF) are often dysfluent. We investigated the possibility that providing visual feedback in addition to DAF would reduce speech disruption. Participants repeated sentences while they heard their auditory feedback delayed with and without simultaneous visual feedback. Replicating previous work, DAF led to increased sentence durations and an increased number of speech disruptions. Results showed that visual feedback did not reduce DAF effects on duration, however, a nonsignificant trend was observed that indicated fewer speech disruptions occurred when visual feedback was provided. This trend was significant in speakers who were overall less affected by DAF. These results suggest the possibility that speakers can strategically use alternative sources of feedback.