We are conducting a legal review of the use of sound on Sketchfab, and have to temporarily disable sound on all models.
We are aware that the huge majority of sounds are not infringing, but out of an abundance of caution on the advice of our lawyers, the feature will remain disabled until we can determine the next steps. There is no need for action or proof of ownership.
We hope to bring back sound soon and will notify you when that happens.
Update: We have shared two code examples on how to add sound to your models using the Viewer API: