A new portable device that reduces speech speed in real time has been developed to aid hearing-impaired listeners. The device employs realtime digital signal processing to expand the time scale of the speech signal without changing the pitch. Seven out often elderly hearing-impaired listeners have shown improvements in word discrimination tests when using this speech-rate conversion. The subjects' temporal resolution showed a correlation with the observed improvement, with a coefficient value of 0.859. The results suggest that this device provides support at the cognitive level of the auditory system.