Word discrimination task
Phonological AX discrimination in noise was measured using a task similar to that developed by Tremblay and colleagues [Three different signal-to-noise ratios (SNRs; +3 dB, 0 dB and -3 dB), calculated as the ratio of pressure signal to pressure noise, were utilized in the study. The audio files for the words were edited using PRAAT script to normalize root-mean-square (RMS) intensity at 70 dB sound pressure level (SPL). The audio files for noise were edited to normalize the RMS intensity to 67, 70, or 73 dB SPL. Thus, word intensity was constant, while noise intensity varied across trials to mimic a real-world situation. The sound level was adjusted at 70 dB SPL for all participants.To utilize the dual-microphone directionality feature of the PSAPs, words were presented simultaneously through two speakers (Control 1 Pro, JBL, Los Angeles, CA, USA) placed in the front corners, while background noise was played through two speakers in the back corners of the soundproof room. This configuration was used to create a complex immersive auditory experience. All speakers were located approximately 1.5 meters from the participant’s head, with a height of 1.2 meters and an angle of 45°. To ensure that the participant remained seated and looked straight ahead without turning slightly toward the speakers, participants were instructed to focus on a fixation cross on a computer screen throughout the task. Video monitoring was used to ensure that participants complied with task instructions.Two versions of the same task were created, one for each testing session. In both versions, the material was the same, except that the order of the words in each pair was reversed, and the pairs were presented in different SNRs. In both sessions, the experiment began with a practice block of 16 trials. The main task was divided into three blocks of 10 minutes each, with a short break between blocks. A total of 306 pairs were presented in both sessions, including 102 pairs in each SNR condition. In each trial, the babble noise began to play for 1000 milliseconds (ms), and then the two words were presented with an inter-stimulus interval of 300 ms. After the words were presented, participants were asked to determine whether the words were the same or different using a response box (Cedrus, model RB-530). A white fixation cross centred on a dark gray background was presented during the words, followed by a green question mark (?) to instruct participants to respond. The inter-trial interval was 1000 ms. Participants had a maximum of 3 s to respond. All stimuli and experiment files are available at 