According to his discography page, Owl City founder and singer Adam Young is the creator of iOS 7’s sounds. While the visual design changes are most evident in the new operating system, another noticeable change is how most of the regular sounds are revamped and a slew of new ring and text tones are included. Even before Young was revealed as the creator, many noted how the sounds seemed like Owl City’s style:
It is uncertain if Young created all of the tones and sounds, but his involvement in the development alongside Apple has now been made public.
Update: This entry has removed from Young’s list, likely at Apple’s request.