Effect of Digital Noise Reduction and Directionality on Acceptable Noise Level and Recognition of Digit in Noise

Despite the recent advances in digital processing of hearing aids, a large number of users are not happy with their hearing aids. One of the major reasons for this is the lack of good recognition of speech in noisy environments. Digital noise reduction and directionality are some of the technologies that are helpful in this issue. The present study was conducted to evaluate the effects of these two technologies on listening comfort and speech recognition of individuals with moderate sensory-neural hearing loss. In the current study, we applied Acceptable Noise Level (ANL) and Farsi Auditory Recognition of Digit in Noise (FARDIN), as measures of listening comfort and speech intelligibility, respectively, on 18 participants (8 male and 10 female) who had moderate sensory neural hearing loss. We evaluated both these measures under six different hearing aid conditions: 1) Omnidirectional-DNR/off (baseline), 2) Omnidirectional-Broadband DNR, 3) Omnidirectional-Multichannel DNR, 4) Directional, 5) Directional-Broadband DNA, and 6) Directional-Multicellular DNR. Both the digital noise reduction technology and the directionality improved the ANL, but the effect of directionality was more than the other. None of the digital noise reduction or directionality could improve the score in FARDIN test, but it did not make the results even worse. According to the results, since these two technologies improve listening comfort and do not affect speech comprehension, it is recommended that these two options be activated for adjusting the hearing aid in clinics.