portable sound systems 
Small self-contained sound reproduction equipment that can be carried easily from one place to another.
portable compact disc player
Portable CD player.
Small speakers placed directly over the ears to listen to sounds from the player.
Liquid crystal display showing instructions for setting or operating the player.
portable digital audio player
Portable player for digital music files.
Portable radio with a built-in alarm clock whose wake-up mechanism is a buzzer or a radio station setting.