# Tests of the Influence of DAF (Delayed Auditory Feedback) on Changes in Speech Signal Parameters
###### Contents  
* 1 Introduction
* 2 Motor activities such as speech and articulation are highly complex operations that not only rely on precise neuromuscular coordination but also exemplify how natural language interactions support adaptive behavior in complex cyber-socio-technical systems [1]. Their proper functioning directly depends on the structure and functionality of the speech apparatus and the auditory system [2], which, when working in cooperation, enable accurate articulation of words and sentences. One example of speech disorders is stuttering, which may be caused by genetic mutations [3], atypical brain activity [4], or sensorimotor changes, including alterations in auditory information processing and speech rhythm [5]. Research on speech disorders, as outlined in the new WHO guidelines in ICD-11, emphasizes the need for detailed descriptions and classifications of speech disorders, considering their diverse symptoms and severity. This approach highlights the significance of speech disorders and facilitates a better understanding of these conditions, which is critical in globally improving the quality of life for individuals with communication difficulties [6]. Delayed Auditory Feedback (DAF) is a sensory modification characterized by a precisely defined delay in auditory feedback, which can range up to 500 ms [7]. Numerous studies in the literature have addressed the selection of appropriate delay intervals to elicit the DAF effect. Table 1 presents a selection of relevant articles along with the specific delayed used. For clarity, a 0 ms condition is not listed, as its inclusion is typically implicit. These findings support the rationale behind the delay intervals chosen by the authors, as described in the Study Design section. The article opted for delays of 180, 250, and 360 ms, as delays below 100 ms did not significantly affect the subjects. In a recent article from 2022, authors [PERSON], [PERSON], [PERSON], and [PERSON] examined auditory cortex activation along with the DAF effect for delays of 50, 100, and 200 ms. Activity in the auditory cortex (STG) increased with increasing delay--for a delay of 200 ms, neural activation, prolongation, and speech fluency impairment were most noticeable [16]. The phenomenon of Delayed Auditory Feedback remains the only known research tool capable of inducing stuttering symptoms in healthy individuals. At the same time, several  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Authors** & **Title** & **Delayed [ms]** \\ \hline [PERSON], [PERSON] & Factoral Analysis of the Delayed & 85, 170, 255, \\ [PERSON] & Speech Feedback Phenomenon [8] & 340, random \\ [PERSON], [PERSON], & Stability of Susceptibility to DAF [9] & 80, 180, 280 \\ [PERSON], [PERSON] & Effect of Different Delayed Auditory & 10, 13, 18, 20, 27, 35, \\ [PERSON], [PERSON]. & Feedback Intervals on a Music & 48, 55, 65, 75, 85, 105 \\ [PERSON] & Psych  
studies suggest that the appropriate use of DAF in speech therapy effectively supports individuals with fluency disorders, enhancing communication quality [15]. A notable advantage of this phenomenon is its potential application in home settings, making therapy more accessible. Regular training sessions with DAF can lead to significant improvements in speech fluency [17]. Speech disorders, such as stuttering (ICD-10), are the most common fluency disorders, affecting approximately 0.76% of the population [18]. It is worth noting that discrepancies in data are reported in the scientific literature--some sources suggest that stuttering may affect between 1% and even 5% of the population, which allows for the assumption that it pertains to a small percentage of individuals [19]. Another disorder currently undergoing clear identification, cluttering (ICD-10 F98.6, ICD-9307.0), is observed in 5-16% of the population [20]. The therapies currently available are tailored to the needs of patients and depend, among other factors, on age and the underlying cause of the disorder.