I have Dell Notebook, I’ve had no sound on my laptop for several months. I had to replace the motherboard recently, and had hoped that would fix the problem, but no, I would be grateful for any and all suggestions!
Have you checked the speakers for any sign of damage? Is it just when using the built in speakers that your not getting any sound or is it also when you have headphones plugged into the headphone socket?
Go into the device manager and see if any conflicts are showing, also download the sound driver from Dell for you’re system and reinstall it, that often cures issues where sound drops out, so see if that helps.
First check your sound device driver in device manager. My computer > right click > manage. If there is no driver, download it from website install it. If still there is problem than visit the hardware engineer.
have you tried different apps like games or watching a movie? sometimes there is problem between the graphics card and sound card. Or you could just get yourself external ones 
- Try with headphones
- Check the volume control maybe it’s set at mute or very low volume
- Reinstall the sound drivers.
if you use internal speaker check it
check first your wire
check you Adapter that is work properly.
just contact to service center for the same because specialist will tell you the solution of this problem
If all else fails buy a usb soundcard for it.
try to install a new Operating System… Clean Install