Hello Fahad Al-Riyami,
We do indeed want to ensure that sound is being played back properly through your audio devices from our Surface Laptop. I currently am using some Skullcandy Hesh2.0 headphones with the original audio-jack cable they came with, as well as some basic ear-bud headphones for testing this. We've found that at 100% volume on the Surface Laptop as well as 100% in any music/video/audio playback software, while holding the Skullcandy headphones about 2-3 feet away, is very audible. Also it's almost too loud at 100% using the ear-buds to keep in ears comfortably.
Just to make sure, the audio is turned up within the software being used for audio playback, and not 100% in Windows only, correct? It would also help to know what you are attempting to listen to (Groove Music, Pandora, YouTube etc...).
There are also some applications/features that may be available to install for your headphones depending on the branding or make/model. What kind of headphones are being used with your Surface Laptop at this time?
Thank you~
Mason L.
Microsoft Surface Technical Support