Evaluation of a localization training program for hearing impaired listeners.

ABSTRACT

OBJECTIVE: To evaluate the effectiveness of a home-based and a laboratory-based localization training program. DESIGN: This study examined the effectiveness of a localization training program on improving the localization ability of 15 participants with a mild-to-moderately severe hearing loss. These participants had worn the study hearing aids in a previous study. The training consisted of laboratory-based training and home-based training. The participants were divided into three groups a control group, a group that performed the laboratory training first followed by the home training, and a group that completed the home training first followed by the laboratory training. The participants were evaluated before any training (baseline), at 2 weeks, 1 month, 2 months, and 3 months after baseline testing. All training was completed by the second month. The participants only wore the study hearing aids between the second month and the third month. Localization testing and laboratory training were conducted in a sound-treated room with a 360 degree, 12 loudspeaker array. There were three stimuli each randomly presented three times from each loudspeaker (nine test items from each loudspeaker) for a total of 108 items on each test or training trial. The stimuli, including a continuous noise, a telephone ring, and a speech passage "Search for the sound from this speaker" were high-pass filtered above 2000 Hz. The test stimuli had a duration of 300 ms, whereas the training stimuli had five durations (3 s, 2 s, 1 s, 500 ms, and 300 ms) and four back attenuation (-8, -4, -2, and 0 dB re front presentation) values. All stimuli were presented at 30 dB SL or the most comfortable listening level of the participants. Each participant completed 6 to 8, 2 hr laboratory-based training within a month. The home training required a two-loudspeaker computer system using 30 different sounds of various durations (5) by attenuation (4) combinations. The participants were required to use the home training program for 30 min per day, 5 days per week for 4 weeks. RESULTS: Localization data were evaluated using a 30 degree error criterion. There was a significant difference in localization scores for sounds that originated from the back between baseline and 3 months for the two groups that received training. The performance of the control group remained the same across the 3 month period. Generalization to other stimuli and in the unaided condition was also seen. There were no significant differences in localization performance from other directions between baseline and 3 months. These results indicated that the training program was effective in improving the localization skills of these listeners under the current test set-up. CONCLUSIONS: The current study demonstrated that hearing aid wearers can be trained on their front/back localization skills using either laboratory-based or home-based training program. The effectiveness of the training was generalized to other acoustic stimuli and the unaided conditions when the stimulus levels were fixed.