Hello!Thank you for your question. I am Shefin and I look forward to helping you with your issue today.
Have you tried reinstalling the sound driver?
May I know the make and model number of your computer?
May I know the operating system you are using? Is it Windows 7?
S H E F I N
Please check the bottom of your computer for the model number.
Can I access your computer remotely and check the issue?
Please go to the link below, click Download listed under All-In-One: TeamViewer full version.
After installing it, let me know the ID (E.g 578 467 234) and password (E.g. 2345).
After restarting the computer, check if the sound works fine on youtube.
If the issue persists, or you have any questions, please be back and let me know.If you appreciate my service, please rate it EXCELLENT by clicking the EXCELLENT (5 Stars) and Submit. My goal is to provide you with excellent service – if you feel you have gotten anything less, please reply back, I am happy to address follow-up questions. Thank you for your business!Thank you!S H E F I N