Frequency-altered Feedback Research Articles

Control of vocalization at utterance onset and mid-utterance: Different mechanisms for different goals

A large body of evidence suggests that the motor system maintains a forward model that predicts the sensory outcome of movements. When sensory feedback does not match the predicted consequences, a compensatory response corrects for the motor error and the forward model is updated to prevent future errors. Like other motor behaviours, vocalization relies on sensory feedback for the maintenance of forward models. In this study, we used a frequency altered feedback (FAF) paradigm to study the role of auditory feedback in the control of vocal pitch (F0). We adapted subjects to a one semitone shift and induced a perturbation by briefly removing the altered feedback. This was compared to a control block in which a 1 semitone perturbation was introduced into an unshifted trial, or trials were randomly shifted up 1 semitone, and a perturbation was introduced by removing the feedback alteration. The compensation response to mid-utterance perturbations was identical in all conditions, and was always smaller than the compensation to a shift at utterance onset. These results are explained by a change in the control strategy at utterance onset and mid-utterance. At utterance onset, auditory feedback is compared to feedback predicted by a forward model to ensure the pitch goal is achieved. However, after utterance onset, the control strategy switches and stabilization is maintained by comparing feedback to previous F0 production.

The Effect of Frequency Altered Feedback on Stuttering Duration and Type

The effect of frequency altered feedback (FAF) on stuttering type (i.e., prolongation, repetition, or silent block) and stuttering duration (i.e., average duration of stuttering event and total stuttering time) was examined. Retrospective analyses of previously collected data from 12 adult persons who stutter who participated in an ABA time-series design while reading orally was undertaken. It was hypothesized that stuttering duration would decrease and there would be a differential reduction in the type of stuttering during FAF, concurrent with previously confirmed reduction of stuttering episodes. A total of 2,971 stuttered syllables were analyzed. The total stuttering duration (s/min) was significantly reduced by approximately 50% irrespective of stuttering type (p = .0014). Although significant differences in the average duration(s) of the 3 stuttering types (p = .0064) existed, FAF significantly reduced each type of stuttering by approximately 20% (p = .0055). There was no differential effect on the reduction of proportion of stuttering type during FAF (p = .36). FAF positively affects the speech of persons who stutter by reducing the proportion of stuttered events with a concomitant decrease in duration of residual stuttering and total stuttering time during oral reading.

Auditory-motor mapping for pitch control in singers and nonsingers

Little is known about the basic processes underlying the behavior of singing. This experiment was designed to examine differences in the representation of the mapping between fundamental frequency (F0) feedback and the vocal production system in singers and nonsingers. Auditory feedback regarding F0 was shifted down in frequency while participants sang the consonant-vowel /ta/. During the initial frequency-altered trials, singers compensated to a lesser degree than nonsingers, but this difference was reduced with continued exposure to frequency-altered feedback. After brief exposure to frequency altered auditory feedback, both singers and nonsingers suddenly heard their F0 unaltered. When participants received this unaltered feedback, only singers' F0 values were found to be significantly higher than their F0 values produced during baseline and control trials. These aftereffects in singers were replicated when participants sang a different note than the note they produced while hearing altered feedback. Together, these results suggest that singers rely more on internal models than nonsingers to regulate vocal productions rather than real time auditory feedback.

The effects of frequency altered feedback on reading comprehension abilities of normal and reading disordered children

The effects of frequency altered feedback (FAF) on the reading comprehension levels and error types of normal children and children with reading disorders were examined. Participants read aloud third, sixth, and ninth grade level material in non-altered auditory feedback (NAF) and FAF conditions. Comprehension improved significantly when the reading disordered children read aloud under the FAF listening condition, regardless of the reading level. Significant differences did not occur in reading comprehension for the normal readers under NAF versus FAF conditions. Reading disordered children produced significantly more reading errors as compared to the normal reading children under the NAF listening condition. No significant difference was found in reading errors between groups when reading under FAF regardless of the reading level, suggesting that the FAF signal produced a facilitory effect on reading errors in the reading disordered children. Theoretically, the FAF signal may have activated those cortical regions responsible for the relationship that has been shown to exist between lexical encoding and decoding of verbal and written material, respectively.

Pseudoscience and the SpeechEasy: Reply to Kalinowski, Saltuklaroglu, Stuart, and Guntupalli (2007)

Purpose To respond to several of the issues raised in J. Kalinowski, T. Saltuklaroglu, A. Stuart, and V. K. Guntupalli’s (2007) critique of our previous article (P. Finn, A. K. Bothe, & R. E. Bramlett, 2005). Method Information is provided to refute criticisms raised by Kalinowski et al. about the Finn et al. article, including with respect to that report’s methodology, previous research about fluency-inducing conditions in stuttering, and the SpeechEasy device. Conclusions Available data show that delayed auditory feedback, frequency-altered feedback, masking, and chorus reading can result in reduced stuttering for some speakers, and the inconsistencies and variability in available reports suggest that further careful and creative research could be very valuable. Neither the information about the SpeechEasy provided by its developers, however, nor the manner in which that information has been presented and discussed by its developers rises to the standards of a science-based clinical service discipline.

A survey of Australian adult users of altered auditory feedback devices for stuttering: Use patterns, perceived effectiveness and satisfaction

Purpose. Small portable devices that provide delayed auditory feedback (DAF) and/or frequency altered feedback (FAF) have been developed and marketed to clinicians and people who stutter as fluency enhancing aids for use in everyday speaking situations. The literature contains many laboratory-based reports about the impact of altered auditory feedback (AAF) on the speech of people who stutter but few reports about its use in everyday speaking situations. This paper investigates use patterns and perceptions of the effectiveness and satisfaction with AAF devices.Methods. The current study surveys 14 Australian AAF users.Results. The survey responses revealed varied opinions about AAF devices and their use and effectiveness in everyday speaking situations. Opinions were somewhat related to the type of device used.Conclusions. The results of this study provide some important directions for future research. In particular there is need to investigate the effectiveness of AAF devices when used in conjunction with other traditional treatments.

Auditory feedback control during a sentence-reading task: Effect of other's voice

Graduate School of Information Science and Technology, Hokkaido University,Kita 14 Nishi 9, Sapporo, 060–0814 Japan(Received 21 December 2004, Accepted for publication 7 February 2005)Keywords: Delayed auditory feedback, Transformed auditory feedback, Speech motor control, StutteringPACS number: 43.70. h [DOI: 10.1250/ast.26.358]1. IntroductionSpeech perception plays an important role in speechproduction. When we speak, we always control our voicethrough speech perception in order to adapt our speaking tounpredictable environmental changes. For example, accordingto the Lombard effect [1], pitch or loudness increases under anoisy condition. An artificial change such as a delayedauditory feedback (DAF) or a transformed auditory feedback(TAF) experiments also gives rise to various behaviors ofsubjects. It is known that in the DAF experiment, wherespeech is delayed for a short time (50–300ms) before it isreplayed to the speaker, normal subjects fall into a stuttering-like condition [2]. However, in the case of stutterers,stuttering is suppressed with DAF. In the TAF experiment,where the pitch of the feedback voice is shifted, the pitchfrequency is feedback-controlled with fast (’150ms) andslow ( 300ms) responses [3–5]. Stutterers also demonstratedifferent performance from normal subjects [6]. Thesefindings indicate that complex feedback controls, includingmultiple processing paths, play a part in speech motor controlthrough speech perception.A phenomenon called the ‘‘chorus effect,’’ which isrelated to stuttering, is known [7]. It is a phenomenon inwhich stuttering is suppressed when the stutterer speaks thesame sentences in synchrony with others. The mechanism ofthis effect is not known, however, there are some possibleexplanations for this effect. One is that the brain of stutterersforms a specific structure in the feedback control ofarticulation that does not exist in normal subjects, and it iseffective only under the condition described above. A secondsimpler explanation which is not limited to stutterers is that, ingeneral, the feedback control of articulation is activated onlyon one’s own voice; it does not function when other’s voice isinput to the auditory system. As a result, stutterers who havesome problem in their articulation feedback control system donot fall into stuttering when other’s voice is given. In the lattercase, we can predict that when a parameter of the feedbackvoice is artificially shifted sufficiently to change one’sperception of the voice, the feedback control of articulationwill be suppressed. One of the parameters is pitch. It is knownthat a frequency altered feedback (FAF) medical treatment,where the pitch of the feedback voice is shifted for stutterers,has an inhibitory effect on stuttering [8].Up to now, control models of pitch [4,5] or brainprocessing models of speech [9] have been proposed fromthe viewpoint of speech motor control. However, brainprocessing that explains the chorus effect, such as the twopossibilities above, has not been sufficiently discussed orexamined. The assumption that feedback control of articu-lation acts only on one’s own voice suggests the existence ofanother process of speech motor control that has not beenconsidered until now. Consequently, we report the results ofan experiment in which DAF and TAF were combined toexamine the nature of the interaction between articulationcontrol and pitch-shift perception. Following that, we discussthe mechanism of feedback control on articulation.2. ExperimentIt has been reported from conventional DAF experimentsthat DAF is most effective at delays under 200ms. However,if the feedback control of articulation is suppressed in propor-tion to the pitch shift, the DAF effect will be reduced inproportion to the pitch shift, independently of the delay time.2.1. Experimental methodEight healthy, male native Japanese speakers (age range22–26 years, mean SD 23:5 1:9) participated as subjects.They had no speech or voice disorders, and were not trainedas singers.Each subject’s voice was recorded with a microphone(SHURE SM58). The delay and pitch were converted throughan effector (ZOOM RFX-2000) and fed back to the subjectsthrough headphones (AKG K271S). The parameters of pitchand delay were manipulated using a PC (SONY VAIO PCV-RX72K) through MIDI. The voices were recorded on a DAT(SONY DTC-ZA5ES). Pink noise at 75dB SPL was gen-erated by an analyzer (PHONIC PAA-2) and mixed with thefeedback voice by a mixer (PHONIC PM602FX).Each subject was instructed to read a Japanese junior highschool language textbook. Two conditions were prepared.Under the normal condition, subjects read the textbook aloudwhile listening to an unaltered feedback voice throughheadphones. Under the altered condition, they read the sametext aloud while listening to an altered voice. Under thealtered condition, the sentences were divided into blocks, andeach block was allocated different delay-time and pitch-shift

The Perception of Speech Naturalness of Post-Therapeutic and Altered Auditory Feedback Speech of Adults with Mild and Severe Stuttering

The effect of therapy and altered auditory feedback (AAF) on the perception of speech naturalness of people who stutter was examined. Thirty-five naïve young adult listeners rated speech samples from fluent speakers and individuals who stutter. Samples came from normal adults who spoke Standard American English; adults with mild or severe stuttering who spoke under conditions of non-altered feedback (NAF), delayed auditory feedback (DAF), and frequency-altered feedback (FAF); and adults with mild or severe stuttering prior to and following successful completion of a Precision Fluency Shaping Program. Speech produced under AAF was rated as significantly more natural sounding than speech from the same individuals under NAF (p < 0.0001). Speech produced during FAF was judged to be more natural sounding than that produced during DAF for those with mild (p = 0.003) and severe (p < 0.0001) stuttering. Mild stuttered speech was judged to have more natural-sounding speech than severe stuttered speech during AAF (p < 0.0001). Speech from individuals following therapy was rated significatly less natural sounding than that from individuals during AAF for both mild and severe stuttering (p < 0.0001). The speech of individuals prior to therapy was rated significantly more natural than their speech produced after therapy (p < 0.0001). Speech from normal fluent speakers was rated as significantly more natural sounding than all samples produced from the individuals who stutter (p < 0.0001). These findings support the contention that AAF benefits those who stutter through a reduction of stuttering with a gain in perceived speech naturalness.

Acquired stuttering following right frontal and bilateral pontine lesion: A case study

We report neurological information and experimental data regarding acquired neurogenic stuttering in a 57-year-old male following ischemic lesion to the orbital surface of the right frontal lobe and the pons. The experimental data consist of stuttering frequency measures under various conditions that are well known to enhance fluency in most individuals with developmental stuttering. Specifically, we report data for adaptation, unison reading, delayed auditory feedback (DAF), and frequency altered feedback (FAF). This work is the first published report of such a comprehensive examination of a variety of fluency-enhancing conditions in acquired stuttering. The patient read six 200-word texts under different conditions: Six solo readings (Text 1), five unison readings followed by five solo readings (Text 2), five readings with non-altered auditory feedback (Text 3), five readings with 50 ms delayed auditory feedback (Text 4), five readings with increased FAF (Text 5), and five readings with decreased FAF (Text 6). Results indicate that, unlike the typical situation for developmental stuttering, this individual with acquired neurogenic stuttering did not show increased fluency during an adaptation paradigm or under unison, DAF, and FAF conditions. We discuss possible implications of these findings and emphasize the need for further research on acquired neurogenic stuttering.

Self-contained in-the-ear device to deliver altered auditory feedback: applications for stuttering.

The design and operating characteristics of the first self-contained in-the-ear device to deliver altered auditory feedback is described for applications with those who stutter. The device incorporates a microdigital signal processor core that reproduces the high fidelity of unaided listening and auditory self-monitoring while at the same time delivering altered auditory feedback. Delayed auditory feedback and frequency-altered feedback signals in combination or isolation can be generated to the user in a cosmetically appealing custom in-the-canal and completely-in-the-canal design. Programming of the device is achieved through a personal computer, interface, and fitting software. Researchers and clinicians interested in evaluating persons who stutter outside laboratory settings in a natural environment and persons who stutter looking for an alternative or adjunct to traditional therapy options are ideal candidates for this technology. In both instances an inconspicuous ear level alternative to traditional body worn devices with external microphones and earphones is offered.

Self-reported efficacy of an all in-the-ear-canal prosthetic device to inhibit stuttering during one hundred hours of university teaching: an autobiographical clinical commentary

This manuscript outlines the lifelong battle with severe stuttering and describes a new modality of effective amelioration of the disorder from the standpoint of a university professor and researcher in the field of stuttering. Childhood reactions to stuttering are discussed, along with the educational and vocational impact of stuttering. Ongoing therapy was received throughout the formative years and into adulthood, emphasizing reduced rates of speech. The use of Delayed Auditory Feedback (DAF) was found to induce fluent speech, but was considered only as a tool for decreasing the speech rate to achieve fluency. When fluency under DAF was discovered to be possible at faster speech rates, the possibility that the use of DAF and other forms of altered auditory feedback could themselves have an inhibitory effect on stuttering, without concomitant rate reduction was investigated. An In-The-Canal (ITC) fluency-enhancing device was used that provided DAF and Frequency Altered Feedback (FAF) to produce more fluent speech. After 10 months of use, the author was relatively free from stuttering. Speech was natural sounding, relatively spontaneous and unlaboured with an absence of fear. However, further testing (that is currently underway at various centres) is necessary before generalizations can be made.

Self-reported efficacy of an all in-the-ear-canal prosthetic device to inhibit stuttering during one hundred hours of university teaching: an autobiographical clinical commentary

This manuscript outlines the lifelong battle with severe stuttering and describes a new modality of effective amelioration of the disorder from the standpoint of a university professor and researcher in the field of stuttering. Childhood reactions to stuttering are discussed, along with the educational and vocational impact of stuttering. Ongoing therapy was received throughout the formative years and into adulthood, emphasizing reduced rates of speech. The use of Delayed Auditory Feedback (DAF) was found to induce fluent speech, but was considered only as a tool for decreasing the speech rate to achieve fluency. When fluency under DAF was discovered to be possible at faster speech rates, the possibility that the use of DAF and other forms of altered auditory feedback could themselves have an inhibitory effect on stuttering, without concomitant rate reduction was investigated. An In-The-Canal (ITC) fluency-enhancing device was used that provided DAF and Frequency Altered Feedback (FAF) to produce more fluent speech. After 10 months of use, the author was relatively free from stuttering. Speech was natural sounding, relatively spontaneous and unlaboured with an absence of fear. However, further testing (that is currently underway at various centres) is necessary before generalizations can be made.

Quantitative electroencephalogram of posterior cortical areas of fluent and stuttering participants during reading with normal and altered auditory feedback.

In the left and right hemisphere, posterior quantitative electroencephalogram Beta band activity (13.5-25.5 Hz) of seven adult participants who stutter and seven age-matched normal controls was obtained while subjects read text under three experimental conditions of normal auditory feedback, delayed auditory feedback, and frequency-altered feedback. Data were obtained from surface electrodes affixed to the scalp using a commercial electrode cap. Electroencephalogram activity was amplified, band-pass analog-filtered, and then digitized. During nonaltered auditory feedback, stuttering participants displayed Beta band hyperreactivity, with the right temporal-parietal lobe region showing the greatest activity. Under conditions of delayed auditory feedback and frequency-altered auditory feedback, the stuttering participants displayed a decrease in stuttering behavior accompanied by a strong reduction in Beta activity for the posterior-temporal-parietal electrode sites, and the left hemisphere posterior sites evidenced a larger area of reactivity. Such findings suggest than an alteration in the electrical fields of the cortex occurred in the stuttering participants under both conditions, possibly reflecting changes in neurogenerator status or current dipole activity. Further, one could propose that stuttering reflects an anomaly of the sensory-linguistic motor integration wherein each hemisphere generates competing linguistic messages at hyperreactive amplitudes.

The Effects of Frequency-Altered Feedback on Stuttering

The Effects of Frequency-Altered Feedback on Stuttering

Effect of extended exposure to frequency-altered feedback on stuttering during reading and monologue.

An ABA time series design was used to examine the effect of extended, continuous exposure to frequency-altered auditory feedback (FAF) during an oral reading and monologue task on stuttering frequency and speech rate. Twelve adults who stutter participated. A statistically significant decrease in number of stuttering events, an increase in number of syllables produced, and a decrease in percent stuttering was observed during the experimental segment relative to baseline segments for the oral reading task. In the monologue task, there were no statistically significant differences for the number of stuttering events, number of syllables produced, or percent stuttering between the experimental and baseline segments. Varying individual patterns of response to FAF were evident during the experimental segment of the reading task: a large consistent reduction in stuttering, an initial reduction followed by fluctuations in amount of stuttering, and essentially no change in stuttering frequency. Ten of 12 participants showed no reduction in stuttering frequency during the experimental segment of the monologue task. These findings have ramifications both for the clinical utilization of FAF and for theoretical explanations of fluency-enhancement.

Effect of frequency altered feedback and audience size on stuttering.

The effect of frequency altered feedback (FAF) and audience size on stuttering frequency was examined. Nine adults who stutter orally read to audiences of two, four and 15 people under conditions of FAF (one-half octave shift down) and non-altered auditory feedback (NAF). There was no statistically significant effect of audience size on stuttering frequency (p > 0.05). A statistically significant reduction in stuttering frequency was found under FAF relative to NAF (p < 0.5). Collapsed across audience conditions, stuttering frequency was reduced by 74%. These findings suggest that FAF may be useful as a treatment tool.

Effects of speaking into a passive resonator following exposure to frequency altered feedback

Effects of speaking into a passive resonator following exposure to frequency altered feedback

Fluency effect of frequency alterations of plus/minus one-half and one-quarter octave shifts in auditory feedback of people who stutter.

The effect of frequency alterations in auditory feedback of people who stutter on stuttering frequency was investigated. Twelve participants who stutter read aloud under nonaltered auditory feedback (NAF) and four conditions of frequency-altered feedback ([FAF], plus/minus one-half and one-quarter octaves) at normal and fast speech rates. Stuttering frequency was significantly higher while reading aloud with NAF relative to the four conditions of FAF (p < 0.05). There were no differences among participants' stuttering frequency between the four FAF conditions (p > 0.05). Reductions in stuttering frequency of approximately 50% to 60% were found with FAF relative to NAF. More disfluencies occurred with the fast versus the normal speech rate condition (p = .0007) irrespective of auditory feedback condition. These findings suggest that slight alterations in the frequency of auditory feedback of people who stutter are fluency-enhancing.

Effect of single and combined altered auditory feedback on stuttering frequency at two speech rates

The purpose of this study was to determine if combining delayed auditory feedback (DAF) and frequency altered feedback (FAF) would enhance fluency more than either DAF or FAF alone. Ten stutterers read at normal and fast speech rates under nonaltered auditory feedback (NAF), DAF (i.e., a 50 ms delay), FAF (i.e., a one half octave downward shift), and a combination of DAF and FAF [(COMBO), i.e., a 50 ms delay plus a one half octave downward shift]. Results indicated that stuttering frequency was significantly reduced under all altered auditory conditions at high speech rates relative to the NAF condition. There were, however, no significant differences between the altered auditory feedback conditions (i.e., DAF, FAF, and COMBO). It is suggested that further studies be undertaken to explore the combination of altered auditory feedback conditions, as it may be the case that a floor effect was demonstrated with the singular presentations of DAF and FAF and further improvements in fluency enhancement could not be exhibited in the combined condition. Finally, these findings support the notion that a slowed rate of speech is not necessary for fluency enhancement under conditions of altered auditory feedback.

Effect of Frequency-Altered Feedback on Stuttering Frequency at Normal and Fast Speech Rates

The purpose of this study was to determine the effect of the magnitude and direction of the frequency shift of frequency-altered auditory feedback (FAF) on stuttering frequency at both normal and fast speech rates. Twelve adult male and 2 adult female subjects who stutter read 10 different passages at either a normal or fast speech rate under nonaltered auditory feedback (NAF) and each of four FAF conditions in which the feedback signal was shifted: up one-half octave; up one octave; down one-half octave; and down one octave. Mean stuttering frequency for NAF was significantly higher than mean stuttering frequencies for all FAF conditions (p < 0.05). There were no statistically significant differences between the FAF conditions (p > 0.05). Subjects exhibited significantly more disfluencies under the fast speech rate condition relative to the normal speech rate condition. Future research should examine the relationship between frequency shifts of less than one-half octave and stuttering amelioration.