An evidence-based systematic review of frequency lowering in hearing aids for school-age children with hearing loss

Purpose: We developed 1 clinical question for this review, which addressed the comparison of hearing aids using frequency lowering compared to conventional processing amplification for outcomes of audibility, speech recognition, speech and language, and self- or parent-report for children with hearing loss. Method: We systematically searched 26 databases for studies addressing a clinical question and meeting all inclusion criteria. We evaluated studies for methodological quality and reported or calculated effect sizes when possible. Results: The literature search resulted in the inclusion of 5 studies. We implemented several different frequency-lowering strategies across studies; 2 studies used nonlinear frequency compression, 2 used frequency transposition, and 1 used frequency compression with dynamic consonant boost. Conclusions: Whereas methodological limitations of the included studies preclude the formulation of strong conclusions, findings were generally positive across frequency-lowering strategies and outcomes. Additional high-quality research is needed in this area.