The speech banana is a colloquial term for referring to the frequency and decibel range covered by normal human speech. This term is a reference to the shape that this range takes when it is mapped out on a chart with frequencies on one axis and decibel levels on the other. When people are given hearing tests, the person administering the test pays special attention to hearing loss that falls within the speech banana.
In order to understand the speech banana, it can be helpful to know how an audiogram, a chart of hearing test results, is laid out. The horizontal axis of the chart contains information about frequencies a person can hear, from high to low. The vertical axis provides details about decibel levels the person's ears can detect, charted with the lowest levels at the top and the highest at the bottom. The speech banana is located around one third of the way down the chart.
Someone who has difficulty hearing normal human speech can have difficulty learning to talk, understanding conversations, and learning material that is presented in spoken format. People with mild hearing loss may not realize that they cannot hear normally. Children with hearing loss often struggle in class because they cannot hear the teacher talking, but they don't realize their hearing is impaired because they can hear sounds in other ranges. Regular hearing tests are designed to identify hearing loss early so that interventions can be provided.
When a hearing test is conducted, the results can be charted to show the range of sounds the subject of the test can hear. People with good hearing will have results that are located above the speech banana, meaning that they can hear sounds at both lower and higher frequencies than normal human speech, and lower decibel levels than normal human speech. If hearing test results fall below or within the speech banana, it means that the person may have difficulty hearing people talk.
One approach to hearing loss is to fit the person with hearing aids. Hearing aids are adjusted and tested to generate a new audiogram showing what the person can hear while wearing the hearing aids. The goal is to provide the person with the ability to hear the normal range of human speech to facilitate communication. In other cases, hearing loss may be profound enough that hearing aids cannot provide people with a range of hearing that falls inside the speech banana. These individuals may need people to talk more loudly around them, or they may consider using modes of communication like sign language to facilitate conversation.
When a person's hearing test results are charted, the test administrator often draws an outline around the speech banana to create a visual reference that can be compared with hearing ability. It is important to be aware that it is possible for people to have excellent hearing combined with an auditory processing disorder that makes it difficult to understand speech. For these people, the problem is not hearing loss, but a cognitive disorder that interferes with the way the brain processes sound.