Jerry L. Yanz
David J. Delage
Qualitone, 4931 W. 35th St., Minneapolis, MN 55416
The recent increase in the use of compression amplifiers in hearing aids has created the need for more sophisticated fitting algorithms to help select the hearing aid characteristics---gain, output, compression threshold and compression ratio---most appropriate for individual hearing losses. Conventional prescriptive formulas (NAL-R, POGO, etc.), intended for linear amplifiers, are not adequate. The Independent Hearing Aid Fitting Forum (IHAFF) recently published a protocol for defining these variables using multiple existing clinical instruments, computer software, and normative corrections. In this presentation the Prophet Hearing Aid Fitting System will be described. Prophet was developed to accomplish the goals of the IHAFF protocol, as well as the FIG6 approach of Killion, in a single integrated, PC-based instrument. The system sharpens the accuracy of amplification targets by calibrating all signals in dB SPL with real ear values where appropriate, thereby eliminating any reliance on inherently variable HL norms. In addition to creating acoustic targets, it confirms the fit to target by measuring the response of the hearing aid to a multi-level, speech-noise stimulus.