Effect of Digital Frequency Compression (DFC) on speech recognition in candidates for combined Electric and Acoustic Stimulation (EAS)

Purpose: To compare the effects of conventional amplification (CA) and digital frequency compression (DFC) amplification on the speech recognition abilities of candidates for a partial-insertion cochlear implant, that is, candidates for combined electric and acoustic stimulation (EAS). Method: The participants were 6 patients whose audiometric thresholds at 500 Hz and below were ≤60 dB HL and whose thresholds at 2000 Hz and above were ≥80 dB HL. Six tests of speech understanding were administered with CA and DFC. The Abbreviated Profile of Hearing Aid Benefit (APHAB) was also administered following use of CA and DFC. Results: Group mean scores were not statistically different in the CA and DFC conditions. However, 2 patients received substantial benefit in DFC conditions. APHAB scores suggested increased ease of communication, but also increased aversive sound quality. Conclusion: Results suggest that a relatively small proportion of individuals who meet EAS candidacy will receive substantial benefit from a DFC hearing aid and that a larger proportion will receive at least a small benefit when speech is presented against a background of noise. This benefit, however, comes at a cost - aversive sound quality.