The speech banana is a region in which all the phonemes of the world's languages fall on an audiogram. An audiogram is a graphical representation of a person's hearing acuity at a range of frequencies and loudness levels, and it is generally charted with frequency level (in Hertz on the x-axis and decibel level (dB) on the y-axis. When the sounds of speech or phonemes of all known human languages are plotted on an audiogram, they cluster in a banana-shaped region known as the speech banana.
People with normal hearing acuity can also hear sounds outside of the speech banana. These sounds include ambient natural sounds such as a rustling of leaves in the wind or birds chirping. Artificial sounds outside of the speech banana can include music and mechanical noises (e.g., automobiles, lawn mowers).
Audiologists are primarily concerned with hearing loss that occurs within the speech banana because it can slow the development of a child’s language and speech abilities, and this in turn can profoundly interfere with learning. Hearing loss within the speech banana can also hinder communication capabilities in adults, as in elderly people with age-related hearing loss (presbycusis).