The author's artistic experiment The Hearing Test focuses on detection of high frequency clicking sounds that are emitted by the tips of plants' roots. Scientists have claimed that plants' roots produce high frequency clicks between 20 and 300 kHz by bursting air bubbles. But while the phenomenon has been described, its cause remains unexplained. This lack of knowledge opens up possibilities for multiple interpretations and invites experimental approaches as well as speculation concerning plant intelligence, the role of species-specific hearing and sound as evidence. The article is an extended reflection on the experiment.