Then go to control panel,system ,hardware ,device manager option
There if u find any question mark or exclamation mark in yellow Color that means sound drivers are not installed properly
please reinstall sound drivers properly

or else

If no question mark or exclamation mark then check the cable connections of the speaker to the machine

or else

In control panel , select sound audio devices open it there u have
volume,sounds,audio,voice,hardware options

1)See whether it is mute
2)In audio option select default audio device and recording device
should be same

this should solve u r problem .if it is not solved please let me know u r problem briefly

or else put the model number and brand name followed by drivers search in ww.google.com