It’s amazing how sound affects how we experience things. Of course it does, it’s one of our primary senses.
Some apps don’t use a lot of sound, like Gmail or Instagram (unless the content is video). Others use sound to precision, like Duo Lingo and other gamified apps.
Users engage with what they hear just as much as with what they see. Music and sounds can invoke emotions, memories, feelings and other reactions from users. It’s important we be just as deliberate with our sounds as we are with our visuals.