A double-blind, randomized controlled trial exploring the efficacy of frequency lowering hearing aids in patients with high-frequency hearing loss

Whether linear frequency transposition (LFT) assists individuals with hearing difficulties has been studied for years, but no reliable comparison between LFT hearing aids (HAs) and conventional compression-type HAs has been conducted. Herein, we report on the first, relevant, double-blind, randomized controlled trial on this topic using a large sample size. We compared the efficacies of LFT HAs to those of compression-type HAs in patients with high-frequency hearing loss (HFHL); we also reviewed the literature. A total of 103 patients were randomized into three groups: conventional HAs featuring wide dynamic range compression (control group); HAs featuring LFT (LFT group); and HAs employing both LFT and wide dynamic range compression of high frequencies (combined group). Pure tone averages (PTAs), speech recognition thresholds (SRTs), word recognition scores (WRSs), and Abbreviated Profile of Hearing Aid Benefit (APHAB) inventories were assessed at the initial visit and after 3 months of HA use. Subject preferences in terms of continued use of their HAs were also evaluated. The PTA, SRT, and WRS scores significantly improved in all three groups. No significant among-group differences were evident. The APHAB score significantly improved only in the control group; HA future-use preference was also highest in this group. LFT did not provide an additional benefit for subjects with HFHL over conventional amplification and users preferred conventional HAs featuring wide dynamic range compression.