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

Abstract

Frequency-lowering technology has been around for decades. The primary aim—namely, that of providing high-frequency information to those with severe high-frequency hearing loss—addresses a clinical need most conventional hearing devices are still unable to provide. Early studies with frequency-lowering technology reported mostly unfavorable results, and the devices never gained clinical popularity. However, as hearing aid (HA) technology becomes ever more sophisticated, it is appropriate to reconsider whether frequency-lowering HAs should be an amplification choice in those with high-frequency hearing loss. Recent research is yielding promise with people who wear frequency-lowering devices showing improved speech perception. Questions remain regarding patient candidacy and whether auditory training may result in better outcomes. The author also discusses future clinical directions and research needs for frequency lowering.

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

“…As reported by Simpson (2009), results of these studies on slow-playback hearing aid technology show that 13 of 28 children and 6 of 18 adults reported significant improvements for speech understanding. The range of improvement was 10-20% for word and sentence recognition, which is not entirely different from the results reported by early studies on slow-playback technology (Braida et al, 1979).…”

“…All subjects were required to alternate daily among the two hearing aid programs for two months, thus providing four weeks of wear time for each hearing aid condition. 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.…”

“…Additionally, studies on frequencylowering have traditionally been conducted on subjects with profound hearing loss in the high frequencies. It is possible that the persons with more severe hearing losses may not receive as much benefit from frequency lowering as those with better hearing thresholds (Simpson, 2009). Secondly, many of the earliest frequency-lowering algorithms altered the speech signal in ways that negatively affected important characteristics of speech, such as temporal and rhythmic patterns, fundamental frequency information, and vowel and syllable durations, and did not preserve the necessary contrasts for distinguishing acoustic cues, such as unvoiced and voiced sounds (Braida et al, 1979).…”

“…Previous studies have reported two types of frequency compression: 1) proportional (or ratio) shifting, whereby all frequencies are shifted by the same multiplicative factor (McDermott & Dean, 2000;Turner & Hurtig, 1999), or 2) nonlinear shifting, wherein certain frequencies above a predetermined cutoff are compressed and signals below the cutoff are not compressed (Simpson et al, 2005). At this time, frequency compression via linear shifting has yet to be implemented into a commercial hearing aid device (Simpson, 2009). Only one manufacturer is marketing nonlinear frequency compression in a hearing aid (Phonak AG).…”

Effectiveness of Frequency-Lowering Hearing Aids and Electric Acoustic Stimulation Cochlear Implant for Treating People with a Severe-To-Profound High-Frequency Hearing Loss

“…Nowadays, several makes and models of digital HAs feature FL algorithms [3][4][5]. So, FL HAs now appear as a viable alternative to conventional amplification for people with a severe-to-profound HFHL.…”