Hansen was born in Sydney, Australia, and attended St Andrew's Cathedral School and Newington College.
He continued his musical education with James Bowman, David Harper and Graham Pushee.
Hansen first performed in the United Kingdom in concerts with the Scottish Chamber Orchestra, conducted by Emmanuelle Haïm.
He also performed with Il Complesso Barocco in Fernando by Handel, conducted by Alan Curtis during the Spoleto Festival in Italy.
He also performed in the U.S. premiere of Thomas Adès' The Tempest at the Santa Fe Opera, conducted by Alan Gilbert, Handel's Giulio Cesare at the Theater an der Wien, conducted by René Jacobs, Monteverdi's L'Orfeo at the Berlin State Opera, conducted by René Jacobs, Handel's Semele at the Théâtre Royal de la Monnaie, conducted by Christophe Rousset, in Giovanni Andrea Bontempi's Il Paride at the Innsbruck Festival of Early Music, directed by Christina Pluhar.