The intent of Justin Bieber’s acoustic album is twofold, according to the star: It’s a holiday-timed gift for fans who want to feel closer to their teen idol, but also a response to critics who have panned his sound as overproduced bubble-gum pop. On the former count, “My Worlds Acoustic” succeeds. It repackages the 16-year-old singer’s most intimate songs from his two albums and offers new material in the form of “Pray,” a treacly but well-meaning ballad that taps into Bieber’s spiritual beliefs. Whether it succeeds on the second count is a trickier matter, though, mostly because “acoustic” is a somewhat misleading descriptive. The tracks “Baby” and “One Time” feature extraneous layers of congas and new age-style synths as prominently as they do guitar riffs, and the opportunity to switch up the arrangements of Bieber’s songs along with their instrumentation is missed. The saving grace comes on “Favorite Girl,” precisely because the track is a live recording from the truly acoustic portion of Bieber’s concert. It’s the one moment where you can hear all of the young artist’s strengths falling in line-raw talent, maturing vocals and, of course, an all-too-valuable connection with his fans.