DId you check if your sound drivers are updated ?
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I had this problem too but these instructions didn't work. I then figured out that it was Razer Cortex, which I use too boost my game so I will have less lag. I guess Razer closes down a program that makes the sound work for the Sims 4.
The second tip helped me, thank you so much for posting this :3 Im a real dummy when It comes to computers, but I coud follow these instruction because they were so clear.
March 2016 - last edited April 2016
This is a common problem on systems with multiple audio devices since windows will detect the active device during initialization of applications and if there is any interruption of the device during operation or initialization, the device will be removed from the list and another selected by the application as default. This has been a problem since plug and play was introduced for windows audio devices. The best solution is to deactivate all unnecessary audio devices in your control panel and you may discover devices which you never knew had been installed such as "Nvidia HD Audio" which is installed automatically with unified driver updates.
To disable the device, simply right click on it and select disable, then re-launch your game or multimedia application:
You can prevent installation of these unnecessary devices or uninstall them by choosing the advanced options during driver installation:
Then choosing the components to be updated or removed:
For removal of NVidia software components you must select 'Perform Clean Installation' otherwise the installer will only update the selected components. The 3D Vision and "Geforce Experience" components are unnecessary and can be removed without any concern for game performance or functionality.