My first G752VS OC from Amazon had the same issue. I attempted the various suggested fixes with minimal success. I eventually contacted Amazon and explained the issue. They exchanged the laptop with no hassle. My new G752VS OC did not have any sound issues. I also noticed the volume is much louder on this one. I am not sure if they made adjustments in manufacturing since coming out with these first 10 series graphics laptops but my original 'Check NO#' on box was in the 3800s. The new laptop 'Check NO#' on box was in the 6200s. I would definitely if within your return period contact seller for a replacement. This is why I usually buy through Amazon. They make it hassle free and a great experience.
"It's all 'bits' and 'nibbles' until it turns into a 'Byte'"...Me
"Those who know, do. Those who understand, teach"...Aristotle
Desktop: i7 8700K, ROG STRIX Z370-E Gaming, 16GB G.Skill TridentZ RGB CL14 DDR4, NVIDIA GTX 1080 Founder's Edition, Samsung 960 Pro M2 512GB NVMe, Samsung 960 EVO M2 1TB NVMe, and Win 10 Pro
Laptop: [ASUS G752VS OC] i7 6820K, 32GB DDR4, GTX 1070, Samsung 950 Pro 512GB NVMe, Samsung 850 Evo 500GB SSD, and Win 10 Pro