Recently, portable terminal units such as portable telephones and the like become remarkably popular, and are carried by many people when they go outside.
Also, the portable terminal unit has become capable of providing multimedia services. Because of an increase in memory capacity, incorporation of storage media, an increase in a communication speed and the like, the portable terminal unit can handle a large capacity data such as image, music and the like.
In each of Japanese patent laid-open publication No. 2000-49722 and Japanese patent laid-open publication No. 2000-78301, there is disclosed a stereophonic reproducing technology in which headphones are used with a portable terminal unit.
However, in the above-mentioned conventional technologies, there is a problem that only a person who wears the headphones can listen to stereophonic music, surround sound and the like, but other surrounding persons can not listen thereto.
In order for the persons other than the person wearing the headphones to be able to listen to stereophonic music, surround sound and the like, it is necessary that a single portable terminal unit has a plurality of speakers for propagating sound into space. However, since the portable terminal unit usually has a small size, there occurs another problem that crosstalk becomes large and it is difficult to obtain sufficient stereophonic effect.
Further, there occurs still another problem that, in order to listen to the sound such as the surround sound and the like, it is necessary to connect other speakers to the portable terminal unit.