Listen and watch the video below, in which a tone starts at 20 Hertz and rises to 20 kiloHertz (1000 times higher). This is referred to as the human audio spectrum. You may not hear anything at first, but you will start to hear when your own auditory transduction kicks in. Children are capable of hearing what adults cannot; as we know, hearing capacity diminishes with age. Change the setting (gear-shaped icon) to speed the video up if you want to.