a pair of bellows a roaring in one's ears a purr Velcro opening a freight train engine thunder the furnace cycling on (or, in warm climates, the air conditioner) The transfixing sound of heavy breathing can indicate the presence of a nearby unicorn, as mentioned by Walter Dean Myers in Shadow of the Red Moon (1995). Other accounts of unicorn breathing in literature include: The unicorn blew softly through his nostrils and then spoke! -- Dot Taig, Satylea Scrolls: Lost Soul (2005) He stopped a few feet away, nostrils flaring, breathing heavily. -- Sunblind, "The Unicorn Herd" (2006) The unicorn released a shuddering breath through its nostrils. -- Jedi Boadicea, "Tears of Fire" (2003) The unicorn's voice is breathy, and it reminds you of a breeze in summer. -- Saebrylla (2006) Particularly heavy unicorn respiration could indicate "mouth breathing," which means that you may, after all, be dealing with a unicorn subject to nasal congestion as a result of allergies.