Evaluation of cellular-phone technology with digital hearing-aid features: Effects of encoding and individualized amplification

摘要

Multi-channel amplification was implemented within a cellular phone system and compared to a standard cellular-phone response. Three cellular phone speech-encoding strategies were evaluated: a narrow-band (3.5 kHz upper cut-off) enhanced variable-rate coder (EVRC), a narrow-band selectable-mode vocoder (SMV), and a wide-band SMV (7.5 kHz cut-off). Because the SMV encoding strategies are not yet available on phones, the processing was simulated using a computer. Individualized-amplification settings were created for 14 participants with hearing loss using NAL-NL1 targets. Overall gain was set at preferred listening levels for both the individualized-amplification setting and the standard cellular phone setting for each of the three encoders. Phoneme-recognition scores and subjective ratings (listening effort, overall quality) were obtained in quiet and in noise. Stimuli were played from loudspeakers in one room, picked up by a microphone connected to a (transmitting) computer, and sent over the internet to a receiving computer in an adjacent room, where the signal was amplified and delivered monaurally. Phoneme scores and subjective ratings were significantly higher for the individualized-amplification setting than for the standard setting in both quiet and noise. There were no significant differences among the cellular-phone encoding strategies for any measure.