Effect of Digital Frequency Compression (DFC) on Speech Recognition in Candidates for Combined Electric and Acoustic Stimulation (EAS)

Abstract

Purpose-To compare the effects of conventional amplification (CA) and digital frequency compression (DFC) amplification on the speech recognition abilities of candidates for a partialinsertion 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-Resultssuggest 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. Keywordshearing aids; frequency compression; cochlear implants; amplification; electric and acoustic stimulation (EAS) Approximately 31.5 million individuals in the United States have hearing loss (Kochkin, 2005). The most common losses are at frequencies higher than 1 kHz, for which the most common rehabilitation option is conventional, frequency-shaped amplification. The benefits of conventional amplification, however, vary considerably with the configuration and degree of the hearing loss. Several studies report little or no benefit of high-frequency amplification when auditory thresholds exceed 55-60 dB HL at or above 2000 Hz when speech materials are presented in quiet (Amos & Humes, 2001;Ching, Dillon, & Byrne, 1998;Hogan & Turner, 1998;Turner & Cummings, 1999). Although amplification of high frequencies may be of some benefit in noise (Plyler & Fleck, 2006), listeners with severe high-frequency losses remain at a significant disadvantage in all listening environments.Listeners with greater degrees of hearing loss are at the greatest disadvantage because speech reception is negatively influenced, first, by the high presentation levels used to improve audibility (e.g., Dubno, Horwitz, & Ahlstrom, 2005French & Steinberg, 1947;Hornsby & Ricketts, 2006;Studebaker, Sherbecoe, McDaniel, & Gwaltney, 1999) and, second, by the increased likelihood of damage to inner hair cells in the basal region of the cochlea (e.g., Moore, Huss, Vickers, Glasberg, & Alcántara, 2000). Thus, the use of conventional, frequency-shaped amplification results in the presentation of less intelligible speech to an impaired auditory system. Combined Electric and Acoustic Stimulation (EAS)Despite the shortcomings of traditional amplification, few alternative rehabilitation options have been available to listeners with relatively good l...

Electric-Acoustic Stimulation of the Auditory System: A Review of the First Decade

“…An increase in monosyllable word recognition from 9% best aided with HA in quiet, over 48% in the CI-only condition to 65% under the EAS condition is not unusual [Gstoettner et al, 2009]. But while in quiet, the gain in speech understanding between CI only and EAS is not significant in all cases, the overwhelming advantage of EAS over conventional and even DFL HA becomes clearly evident in adverse listening situations with decreasing signal-to-noise levels [Gifford et al, 2007b;Lorens et al, 2008].…”

“…The only study available so far which compared DFL technology with conventional HA and EAS was published by Gifford et al [2007b]. In their study, 6 subjects showing the typical EAS indication criteria were evaluated in terms of the outcome of CNC scores using conventional and NFC HA.…”

The Contribution of a Frequency-Compression Hearing Aid to Contralateral Cochlear Implant Performance

“…Existing literature indicates that listening time or experience with frequency-lowering signal processing is necessary for listeners to achieve better performance (Braida et al, 1979;Simpson et al, 2009). On average, previous studies have provided four weeks of listening time for listeners to adjust to a new frequency-lowering signal processing strategy using a take-home device (Gifford et al, 2007;Glista et al, 2009;McDermott & Knight, 2001;Parent et al, 1997;Simpson et al, 2005Simpson et al, , 2006. By giving each subject two months in the study while alternating daily among the two hearing aid programs, each signal processing (frequency-compressed and conventional) was used for approximately four weeks.…”

“…More recently, Gifford et al (2007) investigated the use of the AVR Nano frequency-lowering hearing aids for six subjects with steeply sloping losses that fit the criteria for the short electrode CI. Each subject wore the AVR Nano hearing aid for five weeks.…”

Frequency-Lowering Devices for Managing High-Frequency Hearing Loss: A Review

“…In a recent study, the AVR Nano Xp was trialed in 6 adult participants with steeply sloping losses (Gifford, Dorman, Spahr, & McKarns, 2007). Participants were required to have hearing thresholds of 60 dB HL or better at frequencies less than or equal to 0.5 kHz.…”