Each participant will be fitted with the noise reduction program on the same hearing aid. The principle of the noise reduction algorithm is to remove noise from a speech signal with the aim of improving the speech intelligibility and comfort.

Each participant will be fitted with a second noise reduction program on the same hearing aid. The parameterization of this NR algorithm differs from that in NR(1).

Each participant will be fitted with a third noise reduction program on the same hearing aid. The parameterization of this NR algorithm differs from that in NR(1) and NR(2).

Stimuli which contain simultaneous frequency and amplitude modulations of a wide-band noise carrier are presented to the participants.

The depth of the modulations is systematically varied and the individual modulation detection thresholds are recorded as a broadband decibel (dB) value.

For each participant 4 measures were made and averaged to give a mean STM threshold.

The digit-span task is used to measure working memory's number storage capacity. Participants will see a sequence of numerical digits and are tasked to recall the sequence correctly, with increasingly longer sequences being tested in each trial. The participant's span is the longest number of sequential digits that can accurately be remembered, which means that the participant recalls two sequences out of a maximum of three sequences correct. Digit-span tasks can be given forwards or backwards, meaning that once the sequence is presented, the participant is asked to either recall the sentence in normal or reverse order.

The Go/No-go task measures inhibitory control. Participants are asked to respond to a Go stimulus as fast as possible but not respond to a No-go stimulus. Go stimuli are presented at a rate much higher than the No-go stimuli to elicit prepotent motor activity. The outcome measure of this task is the number of commission errors (i.e. responding to a No-go stimuli) a participant commits as a measure of their ability to stop prepotent motor activity.

Blood volume pulse will be recorded from participants during the performance of the auditory task (non-invasively with a photoplethysmographic (PPG) sensor). Analyses will be carried out on the data recorded during a time window following each auditory stimulus (relative to baseline activity). It is planned to analyze event-related changes in pulse rate and amplitude (beats per minute).

Respiration rates will be recorded from participants during the auditory task using a belt placed under the ribcage. This data will only be used to control for changes in breathing patterns which may influence skin conductance measurements.

Skin temperature will be recorded from participants during the auditory task using a small thermometer attached to the outside of the little finger (non-dominant hand). This data will only be used to control for changes in temperature which may influence skin conductance measurements.

Tympanometry will be used to assess the mobility of the eardrum, prior to recording Acoustic Reflex Thresholds (ARTs). Compliance [ml], Middle Ear Pressure [daPa] and ear canal volume [ml] will be recorded and checked that they fall within normal limits. Where this is the case, ARTs will be measured using 0.5, 1 & 2 kHz stimulus tones ipsi- and contralaterally for each ear. The resulting outcome measure will be the threshold [dB] required at each frequency and ear arrangement for a stapedial reflex to be present.

Race and Ethnicity were not collected from any participant.

Hearing Aid with Noise Reduction I (NR) enabled.

Hearing Aid with NR(1): Each participant will be fitted with the noise reduction program on the same hearing aid. The principle of the noise reduction algorithm is to remove noise from a speech signal with the aim of improving the speech intelligibility and comfort.

Hearing Aid with Noise Reduction II (NR) enabled.

Hearing Aid with NR(2): Each participant will be fitted with a second noise reduction program on the same hearing aid. The parameterization of this NR algorithm differs from that in NR(1).

Hearing Aid with Noise Reduction III (NR) enabled.

Hearing Aid with NR(3): Each participant will be fitted with a third noise reduction program on the same hearing aid. The parameterization of this NR algorithm differs from that in NR(1) and NR(2).

Pupil dilations will be recorded from the participant during the performance of the auditory tasks.

Analyses will be carried out relative to the pre-trial baseline (measured one second prior to the onset of the stimulus), in order to account for differences in baseline physiological activity.

It is planned to analyze event-related-pupil-dilations. We use the unit: pixels. The size of a pixel in 1mm^2 is relative to the distance between the eye and the camera. Even though participants heads were placed on a chin rest that was always the same distance from the camera, the distance between the individual eye and the camera can still be different due to differences in participants' anatomies.

Thus, pupil dilation are often reported relative to an individuals' baseline, for example as percent change relative to the baseline.

Therefore, we use the unit: pixels, as the use of mm^2 may be inaccurate.

The data from some participants had to be excluded from the analysis. Due to the noisy nature of physiological data, in some cases we were unable to collect enough valid, artefact-free data to analyse. Where this was the case, we discounted the participant from analyses.

Words recalled correctly: words repeated back by participants are logged and the percentage of words recalled correctly calculated.

By the time this outcome measure was performed, 1 of the original participants had withdrawn from the study.

Therefore, data for 18 participants was analysed.

The sound quality ratings will be assessed with the aid of a Multi-Stimulus Test.

The data, serving as secondary outcome measure, are collected in the laboratory.

The scale ranges from 0 "very bad" to 6 "very good" in increments of 1. Individual sound quality rating from participants are averaged over 3 different acoustic scenes for each hearing aid program.

By the time this outcome measure was performed, 2 of the original participants had withdrawn from the study.

Therefore, data for 17 participants was analysed.

Stimuli which contain simultaneous frequency and amplitude modulations of a wide-band noise carrier are presented to the participants.

The depth of the modulations is systematically varied and the individual modulation detection thresholds are recorded as a broadband decibel (dB) value.

For each participant 4 measures were made and averaged to give a mean STM threshold.

By the time this outcome measure was performed, 2 of the original participants had withdrawn from the study.

Therefore, 17 participants had measurements for this outcome measure made. For 5 participants it was not possible to measure an STM threshold reliably at all test occasions.

Where this was the case, these participants were excluded from analyses.

The Trail Making Test (TMT) is a neuropsychological test of visual attention and task switching. It consists of two parts in which the subject is instructed to connect a set of 25 dots as quickly as possible according to a given order. In version A the order is given by increasing digit number (i.e. 1-25) while in version B the order is given by alternating digits and letters (i.e. 1-A-2-B-3-C…). The data, serving as an outcome measure, are time-to-complete the set in seconds.

The digit-span task is used to measure working memory's number storage capacity. Participants will see a sequence of numerical digits and are tasked to recall the sequence correctly, with increasingly longer sequences being tested in each trial. The participant's span is the longest number of sequential digits that can accurately be remembered, which means that the participant recalls two sequences out of a maximum of three sequences correct. Digit-span tasks can be given forwards or backwards, meaning that once the sequence is presented, the participant is asked to either recall the sentence in normal or reverse order.

The Go/No-go task measures inhibitory control. Participants are asked to respond to a Go stimulus as fast as possible but not respond to a No-go stimulus. Go stimuli are presented at a rate much higher than the No-go stimuli to elicit prepotent motor activity. The outcome measure of this task is the number of commission errors (i.e. responding to a No-go stimuli) a participant commits as a measure of their ability to stop prepotent motor activity.

Blood volume pulse will be recorded from participants during the performance of the auditory task (non-invasively with a photoplethysmographic (PPG) sensor). Analyses will be carried out on the data recorded during a time window following each auditory stimulus (relative to baseline activity). It is planned to analyze event-related changes in pulse rate and amplitude (beats per minute).

Respiration rates will be recorded from participants during the auditory task using a belt placed under the ribcage. This data will only be used to control for changes in breathing patterns which may influence skin conductance measurements.

Skin temperature will be recorded from participants during the auditory task using a small thermometer attached to the outside of the little finger (non-dominant hand). This data will only be used to control for changes in temperature which may influence skin conductance measurements.

Tympanometry will be used to assess the mobility of the eardrum, prior to recording Acoustic Reflex Thresholds (ARTs). Compliance [ml], Middle Ear Pressure [daPa] and ear canal volume [ml] will be recorded and checked that they fall within normal limits. Where this is the case, ARTs will be measured using 0.5, 1 & 2 kHz stimulus tones ipsi- and contralaterally for each ear. The resulting outcome measure will be the threshold [dB] required at each frequency and ear arrangement for a stapedial reflex to be present.