Amplification devices and fitting
AIDS
Participants were fitted with bilateral PSAPs (CS50+, Sound World Solutions, Park Ridge, IL, USA). We used this device because it is one of the most studied PSAPs in the literature, making it easier to integrate our results with the results of previous studies. It is a high-end behind-the-ear sound amplifier with a 16-channel compressor, 16-channel noise reduction, feedback suppression, and a dual-directional microphone that is more sensitive to sounds from the front and less sensitive to sounds from the back. The price is approximately USD300 dollars per device, which is still significantly lower than traditional hearing aids.The participants fitted the bilateral PSAPs themselves. They first selected the most appropriate ear tips from the three sizes (small, medium and large) according to their preferences and comfort level. They then took a hearing test in the PSAPs. The PSAPs were connected through Bluetooth to a mobile application on an iPhone (Apple, Cupertino, CA, USA) called Customizer by Sound World Solutions. Participants pressed a button when they heard a tone in one of the devices. This test is similar to a traditional pure-tone audiometry test in which pure tones of different frequencies are played in each ear separately. Instructions on how to conduct the test were provided in the iPhone app. No guidance was given to participants during the test, as these devices are intended to be fitted at home without the help of a healthcare professional. Although participants received no guidance, they were supervised during the fitting. The majority of participants were able to fit the devices themselves. However, on a few occasions, participants received assistance when encountering difficulties. Occasional guidance was provided to ensure that we were measuring the effectiveness of the devices rather than the participants’ ability to fit them. After the hearing test, the iPhone app automatically sets the gain prescription (amplification) according to the in situ audiometric assessment results using the NAL-NL2 prescription [It should be noted that we did not use objective methods to test the PSAPs fitting process. In other words, we did not assess the consistency of audibility or the extent to which the amplification matched the NAL-NL2 targets. Instead, the study relied on participants’ subjective feedback to confirm the effectiveness of PSAPs. Indeed, after the fitting, participants were asked if they heard a change in amplification, and the experimenter changed the amplification level to confirm that the devices were working properly. Finally, the devices were put into "restaurant mode" to activate the dual directionality of the microphone and were set to the amplification level determined by the app. These options were retained for each task.