When you install Debian 8.2 on the Dell Precision M3800 laptop, audio is muted by default. To unmute it, install the pavucontrol apt package. This will allow you to edit pulseaudio settings directly.
sudo apt-get install pavucontrol
Then run the pavucontrol command
Click the tab “Output Devices”, and use the tiny, hard-to-see scrollbar on the right side of the window to scroll down to “Built in Audio Analog Stereo.” In the upper right corner there is a mute button. Click it to unmute, and audio should play.