Improvements in speech perception with an experimental nonlinear frequency compression hearing device.

The performance of an experimental frequency compression hearing device was evaluated using tests of speech understanding in quiet. The device compressed frequencies above a programmable cut-off, resulting in those parts of the input signal being shifted to lower frequencies. Below the cut-off, signals were amplified without frequency shifting. Subjects were experienced hearing aid users with moderate-to-severe sensorineural hearing loss and sloping audiograms. Their recognition of monosyllabic words was tested using the experimental device in comparison with conventional hearing aids. Of the 17 subjects, eight showed a significant score improvement (p < 0.05), whereas one subject showed a significant score decrease. Some of the improvements may have resulted from the better audibility provided in the high frequencies by the experimental device in comparison with the conventional aids. However, a subsequent study found that increasing the high-frequency gain in the conventional aids did not produce equivalent perceptual benefits.