This paper presents a portable real-time speech rate conversion system for compensating degeneration of hearing intelligibility of elderly listeners who are suffering from listening to rapid speech. This system enables an elderly user to convert a speech rate as desired by him/herself on real time, with invariance in pitch as well as small impairments in quality. Conventional hearing aids are focusing on compensation of decreased hearing abilities of peripheral auditory pathways in the frequency area, while the new system tries to compensate for them with central auditory pathways in the temporal area. When this system is applied to speech accompanied with a picture, temporal discrepancy between the converted voice and the picture can be absorbed by changing the speech rate at every pitch period along a monotone decreasing function from slow to fast. The system is 180x130x65 mm in size. Another feature allows a user to change the speech rate quickly whenever he/she wants to convert at any stage of conversion. This system can be applied to both the Japanese spoken language and foreign spoken languages, and can be used as a listening aid to learn foreign languages.