Justin Bieber's voice is "definitely" changing.

The 16-year-old singing sensation is relying on the assistance of his vocal coach to adapt his music to suit the way puberty has impacted on his speaking and singing, but says he is handling it well.

He told 'Today' show host Matt Lauer: "My voice is definitely changing, gradually. It's definitely lower than last time I was here. I think that everybody's voice changes. It's just how you go through it. I have a great vocal coach that's helping me."

Though the 'Baby' hitmaker's schedule is always packed, he is given one day off a week to live a normal life and while he sometimes struggles to cope with the demands of being an international pop icon, he hopes he can make his younger stepsiblings, Jaxon and Jazmyn, proud.

He said: "I make sure I have at least one day off a week. I need one day of downtime. The rest of the week is all jam-packed. I have to have at least one day. It's hard because I'm away from my family, like, my brother and sister. You only live once, but at the same time, my brother and sister are going to grow up and they're going to be proud of me."