Listen for humdrum humming. The garden variety call of a unicorn is, by definition, ordinary. As with contemporary classical music, the tones may sound monotonous to the untrained ear. In To Light a Candle (2005), Mercedes Lackey describes a unicorn's voice as "bland." The challenge for the listener is to distinguish unicorn humming from other environmental sounds, such as the humming of insect wings. If you hear a loud swarm of bumblebees when no bees are visible, it may be a unicorn. Accounts of humdrum unicorn humming in literature include: Whispering behind him sounded like the humming of insects: unimportant, beneath his notice. He did not hear the words spoken. Whisper of footsteps, and the unicorn lifted its head. -- Lara Bartram, "Once In a Lullaby" (2004) Note the "monotonous" regularity is this waveform of a unicorn's humming.