I got my surface 3 last summer and the built in speakers worked. I haven't tried using sound for a few months but just tried to listen to you tube videos and other videos on the net and no sound at all. The speakers are at 100% volume, and on control panel speakers are turned on at full volume. Also on keyboard volume button has speakers on at 100. What could be wrong? Don'tt know what atom is but i have windows 10. Tried to put this post in the help forum but it got closed, so guess its staying here.
If you don't know what Atom is I am in doubt if you have the Surface 3 or the Surface Pro 3. Atom is the CPU used in the Surface 3.
Perhaps your sound is connected to a bluetooth device. I would expect that is something one doesn't forget nor do accidentally, but hey...let's give it a shot.
In Windows check the right bottom corner (system tray) and see if you can find the speaker icon. If not click the up arrow and it should be there. Then right click it and select "Playback devices". In the list check if everything is available and if the speakers have the check marking they're set as default. I'll have to translate from my Dutch machine to English here. Right click the device that you want to use and hit "Test". See if the indicator shows green bars (indicating a sound is being played) and if you hear sound.
If you don't see the device that you want to use right click anywhere in that screen where you would expect a list of devices and check to see if disabled devices and not connected devices will be shown. Tick both check boxes.
If that all doesn't work out please post a screen shot of the screen that I just described.