Real ear measurments (REMs) or the probe microphone measurments is an objective method to verify hearing aids fitting taking into account the ear canal acoustics of the patient.(1) It is the best method to provide a patient with an audible signal.(2)
Prescriptive fitting formulas, such as NAL-NL1, NAL-NL2, and DSL V5a are evidence-based methods for determining how much amplification is needed for a particular hearing loss. By using prescriptive formula verified with REMs at the initial hearing aid fitting allows the audiologist to ensure audibility for conversational speech, to set appropriate amounts of amplification for soft sounds, and to prevent loud sounds from becoming uncomfortable.(3)
Some audiologists use the first-fit formulas of the manufacturer to have a proper fitting gain, however, many studies revealed that the first fit of the manufacturer is insufficient for the required gain.(4)
Self-report outcome measure is also mandatory to determine the benefit of hearing aids.(5) The Abbreviated Profile of Hearing Aid Benefit questionnaire (APHAB) is used to measure disability caused by hearing loss and measure the reduction of that disability by using hearing aids. The APHAB uses 24 elements including 4 dimensions: ease of communication, reverberation, background noise, and aversiveness to sounds.(6)