# Tests of the Influence of DAF (Delayed Auditory Feedback) on Changes in Speech Signal Parameters
## 3 Study Design  
The study group consisted of university students (mean age: 22 years), all of whom were native speakers of Polish. The participants had no speech, hearing, vision, or neurological disorders. All were open to participating in the study and provided their consent. As required by the Polish legislation [24], written informed consent was obtained from all participants prior to their involvement in the study, including consent for the processing  
Figure 2: Screenshot of the DAF application during testing with a selected delay of 250 ms.  
of personal data. The participants were provided with comprehensive information regarding the study's objectives and scope. The research carried no health risks, and participation was strictly voluntary [25]. The investigation examined delays of 0 ms, 180 ms, 250 ms, and 360 ms, where 0 ms represented natural speech. The participants wore headphones that isolated them from external sounds, focusing their attention entirely on auditory sensations. The tasks assigned to the participants included engaging in short conversations, describing a picture, and reading--both in natural speech and under delayed auditory feedback conditions. Before the study began, the participants were informed about the procedure and provided with guidelines to ensure smooth execution. They were instructed to maintain a consistent distance from the microphone and avoid deviating from the specified distance between their mouths and the transducer. They were asked not to laugh during their speech, to speak loudly and clearly, maintain their natural pace, avoid rustling the paper containing the text, and refrain from tapping or stomping. Recognizing that the study could induce stress in the participants, a stress-relief tool in the form of an elastic band was provided. This allowed the participants to channel their emotions without disrupting the study. The band did not introduce motor noise, and hand movements were not recorded in the acoustic signal. These measures were designed to prevent extraneous sounds that might interfere with the recorded speech samples. The participants were reassured that speech difficulties arising under delayed auditory feedback were expected, ensuring they did not focus excessively on verbal impairments. The study began with spontaneous speech to familiarize the participants with the experiment's structure. This was followed by Delayed Auditory Feedback (DAF) with delays of 180 ms, 250 ms, and 360 ms, applied in random order to prevent the participants from predicting the delay or its level of difficulty. A short conversation was conducted at the start of the test, focusing on natural topics familiar to the participant. The dialog was designed to encourage a conversation rather than interrogate the participant, helping to alleviate stress and \"warm up\" the speech apparatus. This section was not analyzed, as its purpose was to prepare the participants for subsequent stages of the study. The next stage involved describing photographs selected to minimize ambiguity about their content. Participants were not informed beforehand about the images and were required to describe them spontaneously as the visual stimuli were presented in a randomized sequence. The images used in the study were frames from cartoons familiar to the participants, ensuring contextual recognition. Each of the photos described was taken into account when analyzing the results. Before this task, the participants were advised to provide descriptions as detailed as possible for a later analysis. This part aimed to assess creativity, unconventional ideas, and the ability to divide attention during spontaneous speech. The final task involved reading two texts: a poem and a book advertisement. The poem consisted of 110 words and 209 syllables, with a Flesch-Kincaid Grade Level (Fog Index) of 6, indicating that the language was very simple and appropriate for primary school students. The book advertisement contained 139 words and 295 syllables, with a Fog Index of 9, classifying it as simple and accessible.