Evaluation of a frequency transposition algorithm using wearable hearing aids.

Transposition of acoustic information from higher to lower frequencies may help people with severe or profound high-frequency hearing loss, especially when a 'dead region' is present. Previously, we (Robinson et al, 2007 ) evaluated the benefit of an FFT-based transposition algorithm in a laboratory study. Although results were promising, we hypothesized that further training and exposure would be needed to gain the full benefit. This was tested here by implementing the algorithm in wearable digital hearing aids. Five subjects with high-frequency dead regions used the aids for five weeks. Performance on the transposing and control conditions was compared objectively using speech tests (vowel-consonant-vowel, 's' detection, and speech in noise) and subjectively using questionnaires. Overall, the results showed no benefit with the transposition even after experience. Subjective preference was generally for the control condition.