Purpose : In this study, when the compression threshold (CT) was set high and low for sensorineural hearing loss (SNHL), which uses hearing aids for the first time, evaluated the effects of electro-acoustic adjustments such as word recognition scores (WRSs), K-IOI-HA (Korean version of international outcome inventory for hearing aids) (Chu et al., 2012), K-PHAB-Q (Korean version of profile of hearing aid benefit-quick version) (Kim & Lee, 2020), K-PHAB-Q), sound quality (sound quality, sentence clarity, and loudness of noise).
Through this study, it was intended to help the CT adjustment of hearing aids, and further to help improve the communication ability of hearing impaired in various listening environments.
Methods : A total of 20 patients consisting of 11 men and 9 women with bilateral SNHL participated in this study. The mean average age of participants was 75 years with the standard deviation of 8.08 ranging from 49 to 88 years old. The combined average of pure tone average was 63.9 dB HL with the standard deviation of 13.51 dB HL. All participants had no prior experience with hearing aids.
CT control method was performed through gain for 55 dB sound pressure level (SPL). CT was controlled in two groups, with one group initially controlled to low CT (around 50 dB SPL) and the other to high CT (around 60 dB SPL). And after 4 weeks, CT reversed. During the adjustment process, the overall volume and frequency response curve were adjusted by the subjective response of the subjects, such as the loudness and sound quality of the conversational sound. Additionally, insertion gains, 5 dB and 10 dB word in noise evaluations and hearing aids performance diagnosis as well as surveys (K-IOI-HA and K-PHAB-Q) were conducted at week 4 and week 6.
Results : The results of this study are summarized as follows based on when the gain for 55 dB SPL was small, that is, when high CT.
First, It has been shown that the noisy WRS was improved significantly. However, when analyzed individually due to the small differences, it was found that there were more subjects with improved noisy WRS at high CT.
Second, it was found that LC was improved among K-PHAB-Q.
Third, it was found that the loudness of the noise was improved significantly and the noise was felt small.
Conclusions : The results of the study suggest that when gain adjustment of multi-channel hearing aids at the hearing rehabilitation center, the gain for small conversation levels as well as the gain for the overall or normal conversation level needs to be adjusted considering the individual's draft and psychoacoustic characteristics. However, for effective adjustment of CT, it is necessary to verify the suitability of hearing aids or assess the effectiveness of hearing aids on recognition of quiet or noise environments, hearing loss preference, satisfaction before and after wearing hearing aids, and changes in communication abilities in various environments.
The results of this study are thought to be able to be used as basic data when determining the effective CT of hearing aids worn by SNHL at the hearing aid centers, and calculating the hearing aid fitting formula.