Although there have been tremendous development of hearing aid technology, it is important to understand features of non-linear hearing aid technology and to adjust various electroacoustic parameters when fitting hearing aids. The author described changes of dynamic range, signal-to-noise ratio and consonant-to-vowel ratio by adjustment of compression ratio (CR), compression threshold (CT), attack time (AT) and release time (RT) in non-linear hearing aids using Korean sentence waveforms. In addition, the author suggested effective methods to determine CR, CT, AT and RT in non-linear hearing aid fitting for children and adults with hearing loss. Further, to maximize communication abilities of hearing-impaired, especially Korean children and adults with hearing loss, future researches are needed regarding to understanding of Korean language, Korean version of hearing aid fitting fomulae, and aural rehabilitation programs.