Altered Auditory Feedback Conditions Research Articles

Auditory imagery ability influences accuracy when singing with altered auditory feedback.

In this preliminary study, we explored the relationship between auditory imagery ability and the maintenance of tonal and temporal accuracy when singing and audiating with altered auditory feedback (AAF). Actively performing participants sang and audiated (sang mentally but not aloud) a self-selected piece in AAF conditions, including upward pitch-shifts and delayed auditory feedback (DAF), and with speech distraction. Participants with higher self-reported scores on the Bucknell Auditory Imagery Scale (BAIS) produced a tonal reference that was less disrupted by pitch shifts and speech distraction than musicians with lower scores. However, there was no observed effect of BAIS score on temporal deviation when singing with DAF. Auditory imagery ability was not related to the experience of having studied music theory formally, but was significantly related to the experience of performing. The significant effect of auditory imagery ability on tonal reference deviation remained even after partialling out the effect of experience of performing. The results indicate that auditory imagery ability plays a key role in maintaining an internal tonal center during singing but has at most a weak effect on temporal consistency. In this article, we outline future directions in understanding the multifaceted role of auditory imagery ability in singers' accuracy and expression.

The impact of task automaticity on speech in noise

In the control of skeleto-motor movement, it is well established that the less complex, or more automatic a motor task is, the less variability and uncertainty there is in its performance. It was hypothesized that a similar relationship exists for integrated cognitive-motor tasks such as speech where the uncertainty with which actions are initiated may increase when the feedback loop is interrupted or dampened. To investigate this, the Lombard effect was exploited to explore the acoustic impact of background noise on speech during tasks increasing in automaticity. Fifteen healthy adults produced five speech tasks bearing different levels of automaticity (e.g., counting, reading, unprepared monologue) during habitual and altered auditory feedback conditions (Lombard effect). Data suggest that speech tasks relatively free of meaning or phonetic complexity are influenced to a lesser degree by a compromised auditory feedback than more complex paradigms (e.g., contemporaneous speech) on measures of timing. These findings inform understanding of the relative contribution speech task selection plays in measures of speech. Data also aid in understanding the relationship between task automaticity and altered speech production in neurological conditions where dual impairments of movement and cognition are observed (e.g., Huntington’s disease, progressive aphasia).

Lexical-perceptual integration influences sensorimotor adaptation in speech.

A combination of lexical bias and altered auditory feedback was used to investigate the influence of higher-order linguistic knowledge on the perceptual aspects of speech motor control. Subjects produced monosyllabic real words or pseudo-words containing the vowel [ε] (as in “head”) under conditions of altered auditory feedback involving a decrease in vowel first formant (F1) frequency. This manipulation had the effect of making the vowel sound more similar to [I] (as in “hid”), affecting the lexical status of produced words in two Lexical-Change (LC) groups (either changing them from real words to pseudo-words: e.g., less—liss, or pseudo-words to real words: e.g., kess—kiss). Two Non-Lexical-Change (NLC) control groups underwent the same auditory feedback manipulation during the production of [ε] real- or pseudo-words, only without any resulting change in lexical status (real words to real words: e.g., mess—miss, or pseudo-words to pseudo-words: e.g., ness—niss). The results from the LC groups indicate that auditory-feedback-based speech motor learning is sensitive to the lexical status of the stimuli being produced, in that speakers tend to keep their acoustic speech outcomes within the auditory-perceptual space corresponding to the task-related side of the word/non-word boundary (real words or pseudo-words). For the NLC groups, however, no such effect of lexical status is observed.

Auditory plasticity and sensorimotor learning in speech production

Numerous studies have shown the speech motor system to be highly flexible and responsive to changes in sensory input, revealing a central role for both auditory and somatosensory feedback in the acquisition and maintenance of speech motor control. Consistent with these studies, models of speech production have highlighted the role of accurate, stable sensory representations that serve, in part, as the goals of speech movements. A separate (and considerable) body of work has demonstrated that auditory-sensory representations of speech sounds are not perfectly stable, but rather exhibit rapid adaptation to changing input conditions in both children and adults. The plasticity of auditory representations has important implications for the control of speech production, both in early speech motor development and in the sensory-based maintenance of speech accuracy that characterizes adult speech motor control. In this talk, I will describe a series of studies that explore the link between sensory and motor plasticity in the speech motor system. The studies combine the paradigm of sensorimotor adaptation (altering auditory feedback during speech production) with measures and manipulations of auditory-perceptual representations of speech sounds. The results reveal not only that auditory speech targets are flexible under conditions of altered auditory feedback, but that changes in sensory representations can have a direct impact on speech motor learning and performance.

Auditory-Motor Learning during Speech Production in 9-11-Year-Old Children

BackgroundHearing ability is essential for normal speech development, however the precise mechanisms linking auditory input and the improvement of speaking ability remain poorly understood. Auditory feedback during speech production is believed to play a critical role by providing the nervous system with information about speech outcomes that is used to learn and subsequently fine-tune speech motor output. Surprisingly, few studies have directly investigated such auditory-motor learning in the speech production of typically developing children.Methodology/Principal FindingsIn the present study, we manipulated auditory feedback during speech production in a group of 9–11-year old children, as well as in adults. Following a period of speech practice under conditions of altered auditory feedback, compensatory changes in speech production and perception were examined. Consistent with prior studies, the adults exhibited compensatory changes in both their speech motor output and their perceptual representations of speech sound categories. The children exhibited compensatory changes in the motor domain, with a change in speech output that was similar in magnitude to that of the adults, however the children showed no reliable compensatory effect on their perceptual representations.ConclusionsThe results indicate that 9–11-year-old children, whose speech motor and perceptual abilities are still not fully developed, are nonetheless capable of auditory-feedback-based sensorimotor adaptation, supporting a role for such learning processes in speech motor development. Auditory feedback may play a more limited role, however, in the fine-tuning of children's perceptual representations of speech sound categories.

Adaptation to altered feedback in speech

This study focuses on how the control of fundamental frequency (F0) of the voice is influenced by modulations of auditory feedback. A methodology analogous to one used in visual perturbation studies of limb movements was used. In these studies, optical feedback is distorted and subjects adapt to the transformed conditions by relearning the spatial coordinates used in visuomotor control. It was investigated whether F0 control would exhibit an analogous adaptation response to altered auditory feedback conditions. Subjects were exposed to pitch-shifted auditory feedback through headphones while producing (a) sustained vowels and (b) sentence material. The F0 feedback was increased in 2 cent steps that were not noticed by the talkers. Both aural- and bone-conducted masking noise were used to minimize feedback from the true F0. During the transformed feedback condition, subjects decreased their pitch in response to the increasing pitch feedback. However, preliminary analyses did not reveal evidence of adaptation to the auditory transformations. This was examined by unexpectedly introducing normal feedback trials to test for ‘‘aftereffects.’’ Results will be discussed in terms of sensorimotor learning and the role of internal models of sensory feedback in speech motor control. [Work supported by NIH NIDCD Grant No. DC-00594 and NSERC.]

Effect of altered auditory feedback on people who stutter during scripted telephone conversations.

The effect of altered auditory feedback (AAF) conditions on stuttering during scripted telephone conversations was investigated. Nine adult participants made 15 scripted telephone calls to business in New York City. Alterations in the participants' auditory feedback signal were generated by a commercially available digital signal processor (Casa Futura Technologies Desktop Fluency System Model BTD-400) that shifted participants' speech one-half octave down in frequency, produced a 50-ms delay, or produced non-altered auditory feedback. The AAF effects produced by the digital signal processor were not perceived by the recipients of the telephone calls. The proportion of stuttering events per scripted telephone conversations were significantly reduced in the AAF conditions relative to the non-altered auditory feedback condition (p = .0004). Stuttering frequency was reduced by 55% and 60% for the FAF and DAF, respectively. These findings demonstrate the applicability of this technology to situations of daily living involving telephone use.

Effect of monaural and binaural altered auditory feedback on stuttering frequency

The effect of monaural and binaural alterations in auditory feedback on stuttering frequency was investigated. Eleven participants who stutter read aloud under nonaltered auditory feedback (NAF) and monaural and binaural conditions of frequency altered feedback [(FAF), on-quarter octave shift upward] and delayed auditory feedback [(DAF), 50-ms delay] at a normal speech rate. Relative to the NAF condition, reductions in stuttering frequency of approximately 60%-75% were found with the altered auditory feedback conditions. Post hoc single-df comparisons revealed a reduction in stuttering frequency with altered auditory feedback versus NAF (p < 0.0001), a greater reduction in stuttering frequency for binaural compared to monaural altered auditory feedback (p = 0.028), and nonsignificant differences in stuttering frequencies for right versus left monaural conditions (p = 0.54) and DAF versus FAF (p = 0.70).

Stuttering amelioration at various auditory feedback delays and speech rates

The primary purpose of this study was to determine if the finding of Kalinowski et al. (1993) of dramatic reductions in stuttering under delayed auditory feedback (DAF) at normal and fast speech rates could be replicated. The second purpose was to determine if stuttering frequency is differentially affected by various delays in an attempt to identify the optimal delay for fluency enhancement for both normal and fast speech rates. Fourteen adult stutterers read eight different passages at either a normal or fast speech rate under non-altered auditory feedback (NAF) and DAF with delays of 25, 50 and 75 ms. Results showed that significant fluency enhancement occurred under DAF at both normal and fast speech rates at all DAF settings (p < 0.05). This finding corroborates the notion that a slowed rate of speech is not a necessary antecedent for fluency improvement under conditions of altered auditory feedback. In addition, the results indicated that 50 ms appears to be the shortest delay producing the maximum reduction in stuttering frequency.

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.

Effects of alterations in auditory feedback on stuttering frequency during fast and normal speech rates

That stuttering is ameliorated under altered auditory feedback conditions (e.g., masking and delayed auditory feedback) has been known for over 40 years. While this effect was initially attributed to auditory factors, more recent explanations have suggested that a change in speech production, specifically slowed speed rate is responsible. The purpose of this study was to determine if stutterers could demonstrate fluency enhancement under various altered auditory feedback conditions at normal and fast speech rates. Using these rates, stutterers read eight 300‐syllable passages under nonaltered auditory feedback (NAF), delayed auditory feedback (DAF), frequency‐altered feedback (FAF), and a combination of DAF and FAF (DAF+FAF). Results showed that stutterers significantly reduced stuttering under all altered auditory conditions at both speech rates. These results indicate that a slowed speech rate is not necessary to achieve fluency enhancement under altered auditory conditions. Because sensory and motor ev...

Effects of alterations in auditory feedback on stuttering frequency during fast and normal speech rates

That stuttering is ameliorated under altered auditory feedback conditions (e.g., masking and delayed auditory feedback) has been known for over 40 years. While this effect was initially attributed to auditory factors, more recent explanations have suggested that a change in speech production, specifically slowed speed rate is responsible. The purpose of this study was to determine if stutterers could demonstrate fluency enhancement under various altered auditory feedback conditions at normal and fast speech rates. Using these rates, stutterers read eight 300-syllable passages under nonaltered auditory feedback (NAF), delayed auditory feedback (DAF), frequency-altered feedback (FAF), and a combination of DAF and FAF (DAF+FAF). Results showed that stutterers significantly reduced stuttering under all altered auditory conditions at both speech rates. These results indicate that a slowed speech rate is not necessary to achieve fluency enhancement under altered auditory conditions. Because sensory and motor events are inseparable components within the speech process, it is proposed that reduction in stuttering occurs as a result of alterations to both auditory feedback and speech production. [Work supported by NIH-DC-00201 awarded to Haskins Laboratories.]

Effects of alterations in auditory feedback and speech rate on stuttering frequency.

This study investigated the effects of altered auditory feedback on stuttering frequency during speech production at two different speech rates, Nine stutterers, who exhibited at least 5% dysfluency during a reading task, served as subjects. They read eight different passages (each 300 syllables in length) while receiving four conditions of auditory feedback: nonaltered, masking, delayed, and frequency altered. For each auditory feedback condition, subjects read at both a normal and a fast rate. Results indicated that stuttering frequency was significantly decreased during conditions of delayed and frequency altered auditory feedback at both speech rates (p < 0.05). These findings refute the notion that a slowed speech rate is necessary for fluency enhancement under conditions of altered auditory feedback. Considering previous research and the results of this study, it is proposed that there may be two interdependent factors that are responsible for fluency enhancement: alteration of auditory feedback and modification of speech production.