Tehran University of Medical Sciences Auditory and Vestibular Research 2423-480X 24 1 2015 10 04 42 50 EN Marjan Soleimani Department of Audiology, School of Rehabilitation, Tehran University of Medical Sciences, Tehran, Iran Seyyed Jalal Sameni Department of Audiology, School of Rehabilitation Sciences, Iran University of Medical Sciences, Tehran, Iran Farhad Torabi Nezhad Department of Speech Therapy, School of Rehabilitation Sciences, Iran University of Medical Sciences, Tehran, Iran Yahya Modarresi Department of Linguistics, Institute for Humanities and Cultural Studies, Tehran, Iran Mohammad Kamali Department of Rehabilitation Management, School of Rehabilitation Sciences, Iran University of Medical Sciences, Tehran, Iran 2015 10 04 2015 10 04 Background and Aim: As the most perceived and articulated errors of hearing aid users occur in high frequency speech phonemes, this study aimed to find a way to amplify and reconstruct the errors. Thus, the study first prepared a recorded form of two Persian fricative consonants as stimulus; then, the rate of the prescribed gain of the two methods of National Acoustic Laboratories-Nonlinear 2 (NAL-NL2) and the Desired Sensation Level Multistage Input/Output (DSLm[i/o]) were compared. Methods: This study was performed using eight programmed hearing aids for severe sensorineural hearing loss in three configurations: flat, raising, and sloping. After fitting the hearing aids upon the NAL-NL2 and DSLm[i/o] methods, the rate of their gain for the consonants of /s/ and /f/, using Affinity 2.0 analyzer, was determined in 2 cc coupler at the three different levels.  Results: In the flat and raising audiograms, the prescribed gain of DSLm[i/o] for the two consonants in all three speakers and intensity level was more than NAL-NL2 (p< 0.05). In the sloping audiogram, the significance of the difference of prescribed gain of these methods disappeared; however, the DSL m[i/o] in the low frequency area was higher than NAL-NL2 (p< 0.001). Conclusion: The average prescribed gain of methods in the three frequency regions for the two consonants is different, and the prescribed gain of DSLm[i/o] in all frequencies, especially in the low frequency areas, is higher than NAL-NL2. https://avr.tums.ac.ir/index.php/avr/article/view/17 https://avr.tums.ac.ir/index.php/avr/article/download/17/16