Use of frequency transposition in a thin-tube open-ear fitting

The use of thin-tube open-ear fitting has become increasingly popular in the last few years. This type of fitting offers improvements in the wearers’ perception of their own voice, especially for people with a mild hearing loss or a highfrequency hearing loss. It also provides an instant fit, is easy to demonstrate, and improves the appearance of behind-the-ear (BTE) hearing aid to wearers. Both the acceptance rate and the return rate of these models are more favorable than the average for hearing aids overall. Although the openness of the fitting may reduce the potential improvement in signal-to-noise ratio (SNR) offered by a directional microphone, Kuk et al. have shown that an open-fit directional microphone provides an SNR improvement of 2-3 dB over the same hearing aid in its omnidirectional microphone mode. 1 On the other hand, thin-tube open-ear fittings may compromise the audibility of the high frequencies for some wearers. 2 In this paper, we will review some of these potential compromises and discuss why frequency transposition may be a solution for the limitations. We will also show that frequency transposition improves the perception of everyday sounds and may enhance consonant recognition for some people fitted with thin-tube openear devices. ISSUES WITH THIN-TUBE, OPEN-EAR FITTINGS