You can restore the default sound effects following these steps on Spreaker Studio for desktop:
Preferences > Console > Restore default effects

At the moment, it's not possible to restore sound effects on Spreaker Studio for mobile.
You can restore the default sound effects following these steps on Spreaker Studio for desktop:
Preferences > Console > Restore default effects
At the moment, it's not possible to restore sound effects on Spreaker Studio for mobile.