To describe and discuss the evolution of hearing aid prescriptions for gain and compression from the National Acoustic Laboratories (NAL).
✦ The floor
Discussion
Signed responses from readers of the wire.
Audiologists using older NAL prescription targets (NAL-NL1 or NAL-NL2) should be aware that NAL-NL3 represents a philosophically and algorithmically updated standard; reviewing the rationale for the changes can inform more accurate first-fit prescriptions.
Prescription rules like NAL-NL3 are foundational to hearing aid fitting practice worldwide, and understanding their evolution helps clinicians apply them correctly and evaluate when to deviate from defaults.
- 01Narrative review covers the full lineage of NAL prescriptive rules from the original NAL rule to NAL-NL3, published in International Journal of Audiology.
- 02NAL rules aim to optimise speech intelligibility while maintaining overall loudness comfort across a wide range of hearing loss profiles.
- 03Each iteration of the NAL rule has incorporated new evidence on loudness perception, compression, and individual fitting needs.
- 04NAL-NL3 reflects a philosophical shift in how audibility, comfort, and benefit are balanced in the prescription.
- 05The review is positioned as a narrative (not systematic) synthesis, so evidence hierarchies of the underlying studies vary.
The NAL prescriptive framework has evolved through multiple iterations, culminating in NAL-NL3, to better optimise hearing aid gain and compression for speech intelligibility.
guidelinesupportedNAL-NL3 represents an evolved philosophy compared to its predecessors (NAL-NL1, NAL-NL2) in hearing aid prescription.
studypartially supported- PMID
- 42342663
- DOI
- 10.1080/14992027.2026.2690236.
- Journal
- International Journal of Audiology
- Publication type
- review
- Evidence level
- 5
- Population
- Not applicable — narrative review of prescriptive rule development literature
- Intervention
- NAL hearing aid gain and compression prescription rules (NAL through NAL-NL3)
- Comparator
- Sequential comparison of NAL rule iterations (NAL, NAL-R, NAL-NL1, NAL-NL2, NAL-NL3)
Primary outcomes
Philosophical and algorithmic changes across NAL prescription rule generations; Rationale for evolving speech intelligibility and loudness comfort targets