Fitting Formula
A prescriptive algorithm used to calculate target gain and output settings for a hearing aid based on a patient's audiometric data.
Full Definition
A fitting formula is a prescriptive method—most commonly a mathematical algorithm—that translates an individual's audiogram into recommended hearing aid gain, frequency response, and output targets. The goal is to restore audibility for speech across the frequency range while preventing discomfort from over-amplification. Commonly used formulae include NAL-NL2 (National Acoustic Laboratories Non-Linear version 2), DSL v5 (Desired Sensation Level), and the manufacturer-proprietary 'first-fit' algorithms. Editors of clinical protocols and hearing aid fitting documentation must be aware that 'formula' and 'prescription' are used near-synonymously in this context; both forms are acceptable, but the document should be internally consistent.
Usage
Usage note: The plural is 'formulae' in formal and academic writing; 'formulas' is acceptable in clinical and patient-facing documents. Either is defensible, but the document should be consistent.
In Context
- "The audiologist selected the NAL-NL2 fitting formula as the starting prescription for the new device." — Hearing aid fitting report
- "A comparison of two fitting formulae was the primary outcome measure in the randomised crossover study." — Research methods section