# Tests of the Influence of DAF (Delayed Auditory Feedback) on Changes in Speech Signal Parameters
## 4 Result and Discussion
An analysis was conducted on the articulation time of 71 words repeated by each participant. The results showed that for the DAF delays of 250 ms and 360 ms, the articulation time increased for both women and men. In contrast, at the delay of 180 ms, the articulation time was shorter. Notably, the 180 ms delay not only reduced the articulation time but also increased the number of syllables in the overall speech compared to the 0 ms condition (no delay). This observation suggests that the participants were able to articulate more content under a shorter amount of time, indicating improved focus and greater speech efficiency. The study also examined the number of syllables spoken during the description of the photographs. The results indicate that the number of syllables reflected the participants' creativity and their ability to focus on the task or susceptibility to distraction. These data enabled the determination of speech tempo, which, for both women and men, was significantly higher at the 180 ms delay compared to the speech without a delay. These findings suggest that a 180 ms DAF delay may have a positive impact on speech fluency, making it a potentially useful tool for therapy aimed at improving speech fluency. It should be noted that the earlier conclusion is based on a sample of typical speakers. Therefore, further research is necessary to confirm these findings within clinical populations affected by speech disorders. Additionally, jitter and shimmer parameters were analyzed. Jitter refers to irregularities in pitch, while shimmer measures the variation in acoustic wave intensity from one cycle to the next. Both parameters are determined by the characteristics of the vocal folds and are used to assess the extent to which a vowel in speech indicates voice pathology. In  
Figure 5: Standard deviation of formants for vowel ‘A’ at different DAF delay levels in women. Figure 6: Standard deviation of formants for vowel ‘A’ at different DAF delay levels in men. Praat, jitter is calculated based on the actual waveform of the voice signal rather than on a simulated model. It represents the average relative difference between successive pitch periods, thus reflecting the extent to which the duration of vocal fold vibrations varies over time. \[Jitter=\frac{1}{N-1}\sum_{i=1}^{N-1}\frac{|T_{i}-T_{i+1}|}{\overline{T}} \tag{5}\]  
\(T_{i}\)--duration of the i-th period;  
\(\overline{T}\)--average duration of periods. Analogous to jitter, shimmer refers to variations in amplitude between consecutive vocal cycles. It reflects the degree of instability in vocal intensity and is used to assess irregularities in voice signal amplitude over time. Jitter is considered pathological at values exceeding 1.040%, and at values above 3.810% for shimmer. However, the reliability and utility of these parameters are debated, as they are susceptible to technical factors such as microphone interference, microphone quality, software type, and background noise. These circumstances can significantly influence jitter and shimmer measurements [31]. The analysis of the impact of text complexity and Delayed Auditory Feedback (DAF) on speech tempo indicates that both factors significantly influence reading fluency. The data show that as the delay increases, the speech tempo slows down. Notably, at the 250 ms delay, participants in both groups experienced clear difficulties in articulatory fluency. This finding suggests that delays of this magnitude significantly disrupt the natural speech process, leading to reduced speech tempo and extended reading times. As illustrated in Figure 7, the men demonstrated better performance under the DAF conditions in terms of speech tempo compared to the women, which may indicate their greater tolerance to disruptions. However, the effect of delay was equally problematic for both groups when reading texts with lower complexity levels (FOG = 6). This suggests that speakers dedicate more attention to articulation control in simpler texts.