The Speech Banana in an Audiogram

Can you or your child hear sounds within the speech banana? A speech banana is a banana-shaped range on an audiogram that covers the frequencies and decibels that are needed to understand speech. Contained within the speech banana are letters and letter combinations for these sounds.

To understand the speech banana, let's first look at the audiogram. The audiogram is used to graph hearing sensitivity. Frequencies, also called pitch, are measured in Hertz (Hz). The frequencies on the audiogram start at the lower frequencies (or deeper pitches, such as a dog barking or the sound of a lawnmower) on the left and move to the higher frequencies on the right (such as birds chirping or bells ringing); similar to keys on a piano. Moving from top to bottom on the audiogram measures loudness in decibels (dB). The further down on the graph, the louder the sound needs to be in order to be heard. 

All the letters of the alphabet except /q/,/w/, /x/, and /y/ are within the speech banana. Also within the speech banana are the letter combinations /th/, /ch/, /sh/, and /ng/. Those letter combinations can be difficult for deaf and hard-of-hearing people to hear and understand.

Making Sounds Visual

One use of the speech banana is to help visually understand what sounds are not audible. It is an excellent counseling tool for families to understand why their spouse or child seems to hear certain sounds or words but not others. In some cases, audiologists will do aided testing to show what sounds within the speech banana can be heard when using a hearing aid or cochlear implant. This helps you get a pretty good idea how much spoken language your child can understand, but should not be the only type of amplification verification done.

Another audiogram tool that builds on the idea behind the speech banana is the "Count the Dots" audiogram developed by Killion and Mueller in 1990 and updated in 2010. A count the dots audiogram has 100 dots, each representing 1% speech understanding. In areas more important to speech understanding, the dots are closer together. In areas less important, the dots are spread out more. You will notice these dots are in the speech banana range. By overlaying the hearing loss on this connect the dots audiogram and counting the dots that would be audible (those above the hearing thresholds plotted on the graph), you will have an estimate of speech understanding.