Hi there, I'm Tim and will be assisting you today. I have over 15 Years as an Engineer and have been with eBay, DoD and many others. I will do my VERY BEST to help you. If you like i can offer remote access and a call. In addition, with any positive rating I will support your question going forward for free.
Windows 10 has caused issues here and there with up grades, missing drivers would be one of them.
1. Please go here http://www.driverscape.com/manufacturers/hp/laptops-desktops/hp-envy-700-pc/121534
2. Go down to "Audio Drivers"
3. Hit download and put in the pin number to proceed.
4. Install the drivers.
If all is well, please do leave me a rating in the upper right hand corner as i do this for a living, if you still need help, just come back to this page and let me know.