To begin with an attempt at humor, the “speech banana” isn’t a reference to the old skit, “Speak up…I can’t hear you…I’ve got a banana in my ear.” The “speech banana” is a distinctive design appearing on an audiogram. In an audiogram, you usually see the frequency (measured in Hertz) on the x axis, and the loudness (measured in Decibels) on the y axis.
The expression ‘speech banana’ comes from the banana-shaped cluster of points on the audiogram that arises when human language is analyzed. The spoken sounds of most of the letters of the alphabet together with the letter combinations ch, sh, th and ng all fall within this area.
The speech banana is important because it includes most of the sounds of human language which is vital for our communications with each other. People with normal hearing, can also hear lots of sounds outside of the speech banana such as low frequency fog horns or high frequency mosquitos. It is very common for individuals to have trouble hearing or understanding specific vowels and letter combinations such as ng, th, sh and ch.
Because of this hearing specialists and audiologist are most concerned by loss of hearing inside the range represented by the speech banana. If an audiogram exposes that an individual has hearing loss within the speech banana range, it is practically certain that they are having oral communication difficulties.
This is one of the reasons why hearing checks using audiograms are mandated in the schools of many states – to detect possible hearing problems at an early age, when they can be easily corrected. Because this frequency and volume range of sounds is so vital to communications it is the range that most hearing aids are programmed and tuned to perform best in. Make certain you don’t miss any of the human speech in your life by scheduling a hearing exam and audiogram if you believe there is a problem.