but in my ubuntu "Administration" there is no "additional Drivers" option.there is only "hardware driver" option.please help me to install sound driver in ubuntu.i can hear sound with the help of headphone,without headphone I cannot listen the sound.please help me.
You can hear sound with your headphones, it means that sound driver is installed.
Single click on the Speaker icon at the right of your Panel then click on Sound Preference A windows will appear. Click on Output tab and change the Connector properties to Analog Speakers then close. You'll normally hear sound from the speakers now.