This work was performed between November 2019 and December 2020 after being approved by The Research Ethics Committee (No.33498/11/19) and included 60 adults aged 18–60.
Subjects
Patients included in this study were divided into study and control groups (SD and CG, respectively).
CG consisted of 20 adults having bilateral normal peripheral hearing, according to the American National Standards Institute [11].
SG consisted of 40 adults with bilateral symmetrical sensorineural hearing loss.
Inclusion criteria for SG:
Exclusion criteria:
Method
The equipment
-
Sound-treated room: locally manufactured
-
Pure tone audiometry: Madsen Astera, type-1, two channels, and PC-based audiometer with multiple sound field speakers (front-left, front-right, and rear), which are Martin-Audio London type
-
HA: digital multichannel HA with omnidirectional, directional front, and automatic adaptive microphones
Methodology
All subjects were submitted to the following.
Basic audiological evaluation
Hearing in noise test (HINT): we used adaptive testing techniques in accordance with HINT standards of the US House Ear Institute in 1994 [12].
The noise level for CG was constant at 65 dB (A) throughout the test. For SG, the noise level was constant at 75 dB throughout the test (to be heard by all patients as some patients have HL up to 70 dB).
The HINT test material was incorporated into the Astera software, and lists can be selected from the software playlist.
Sentences’ degrees of intensity were modified in an adaptive technique in response to the participant’s response. The initial presentation of the first phrase was at a signal-to-noise (SNR) ratio of − 5 dB. In the first four phrases, the step size was 4 dB. The beginning presentation level for the fifth sentence was determined by averaging the four SNRs from the previous four sentences. The average SNR from the past 5 sentences, with step sizes of 2 dB each, was used to determine the list’s reception threshold for sentences (RTS). According to Nilsson et al. [9] and Hallgren et al. [13], the mean and SD of the threshold stabilize after the fourth or fifth phrase.
To familiarize themselves with the assignment, each participant was given one practice list with noise at azimuth 0° and encouraged to pay close attention and repeat loudly anything they heard as much as possible. The sentences were offered one at a time. If a listener is unsure about what was said, they are advised to make a guess.
Scoring was determined by accurately reporting whole sentences. Minor variations, in verb tense, articles, and singular versus plural nouns, were accepted [14].
The HINT test was done in three situations: signal and noise at 0° azimuth; signal at 0° azimuth and noise at 90° azimuth; signal at 0° azimuth and noise at 270°.
For the SG, these three situations were done in four different conditions using monaural HA. First, the side of monaural HA was considered when collecting data. Then, the noise results at 90° azimuth were calculated by adding the results of noise at 90° azimuth of right HA users to the results of noise at 270° azimuth of left HA users. Finally, and vice versa in noise at 270° azimuth, when collecting data, the results of noise at 270° azimuth were calculated by adding the results of noise at 90° azimuth of left HA users to the results of noise at 270° azimuth of right HA users.
SG condition 1: unaided. Condition 2: aided response with the omnidirectional microphone. Condition 3: aided response with FDM. Condition 4: aided response with AADM.
The three loudspeakers were separated by a 90° azimuth and placed such that the subject’s head center is 1 m from each loudspeaker, just at the subject’s ear level (Figs. 1, 2, and 3).
Statistical analysis
Statistical presentation and analysis of the present study were conducted using SPSS V.22 for the mean value, standard deviation, standard Student “t-test,” and degree of freedom (DF). We have also used the analysis of variance (ANOVA) tests (f), post hoc test, and chi-square test of significance.
