No sound after Ubuntu12.04 is installed

A laptop in the home is upgraded directly from Ubuntu10.10 to Ubuntu12.04. after entering the system, no sound is found. I thought that the upgrade was not successful, and I was too lazy to check the cause. Later I directly burned the InternetdownloadISO image into a CD and installed it directly. I found the same situation. There are several ways to find a solution in Google. After testing, we found that the MasterChannel sound of the AlsaMixer program was turned off, so there was no sound. However

A laptop in the home is upgraded directly from Ubuntu 10.10 to Ubuntu 12.04. after entering the system, no sound is found. I thought that the upgrade was not successful, and I was too lazy to check the cause. Later I directly burned the Internet download ISO image into a CD and installed it directly. I found the same situation. There are several ways to find a solution in Google. After testing, we found that the Master Channel sound of the Alsa Mixer program was turned off, so there was no sound. However, there is no interface to modify after the system is installed. The modification method is as follows:

Execute the alsamixer program under Terminal (you can use ctl + alt + t to execute quickly) and the following screen is displayed:

Use the left and right buttons on the keyboard to move to the Master Channel and control the volume in upper and lower layers. After the adjustment, Press esc to exit the program.