The audio driver may not be loading when comming back from stand by... see if updating it or reinstalling the audio driver helps.
Go to your computer or motherboard manufacturer's website, find the Support, Drivers or Downloads link,.. find your model or type it in the search bar, find the audio driver and download it... to install it see how to in the thread
http://www.tomshardware.com/answers/id-1886474/sound-windows-drivers.html
Also; Stand by memory is saved in the RAM modules and hibernation in the C:\Hiberfil.sys file... Hiberfil tends to corrupt with time, and may cause different types of startup issues.. so disable Hibernation (Control Panel \ Power Options \ Hibernate) next restart the computer and re-enable Hibernation. If you don't have Hibernation enabled, reseat the RAM modules which may be losing Stand By memory.