Using Speech Perception Measures to Guide the Choice of Amplification

The early fitting of infants with hearing aids relies largely on the verification of amplification characteristics using simulated real ear measurements (REM) that are matched to prescription targets derived from audiometric thresholds. The audibility of different parts of the speech spectrum can be inferred from the audiometric thresholds and the estimated applied gain, and is expressed as the speech intelligibility index (SII; ANSI 1997). However, the fidelity of the representation of important temporal and spectral cues within speech is generally not assessed, and detection and discrimination of speech features for the infant or child remain unconfirmed. Thus REM allows verification that the hearing aid gains fit the target, but not the verification of functional benefit for speech intelligibility. The latter requires speech testing, with the form of the test(s) chosen so as to be age-appropriate and to avoid floor and ceiling effects.