October 9th, 2011 by Elizabeth | Tags: Audiology, Baha, Cochlear Implant, Hearing Aids | 6 Comments »
I often say that becoming a parent of a child with hearing loss is like being drafted onto a team for a sport you’ve never played and expected to be the MVP. Almost overnight, you’re bombarded with technical jargon, communication options, opinions, appointments, and waves of emotion. Who wouldn’t be overwhelmed?
Being an adult with hearing loss can be equally mystifying. If you have adult-onset hearing loss, you’ve been launched into a new world. If you’ve had hearing loss your whole life, there’s no guarantee that you have the terminology and adult understanding of things that have been happening to you since you were a child.
One of the first things I like to help parents or adults with hearing loss understand is how to read an audiogram. If we are building speech and language skills on a foundation of listening, it is crucial for all members of the team — including the parents, who are very important team members — to understand the child’s hearing. Adults with hearing loss should also be informed and empowered healthcare consumers.
The audiogram is a graph of how your child hears. Across the top are the frequencies, or pitches, of sounds, from low sounds to high sounds. Down the side are measures of intensity, or loudness, of sounds, from soft sounds to loud sounds. In the middle of the audiogram there is a part called the “Speech Banana.” Most of the sounds of speech fall into that range of pitches and loudness. Our goal is for the child or adult with hearing loss to be able to hear in or above the Speech Banana with hearing aid(s), Baha, or cochlear implant(s) to have access to the sounds of speech. In the speech banana, you can find the sounds a, u, i, sh, s, m, better known as the Ling Six Sounds. These sounds span the length of the Speech Banana. When a listener responds (through a behavioral response or imitation) to a Ling Six Sound Check, we can be reasonably sure that he has access to all of the sounds of speech.
When a child or adult has an audiological exam, many things may take place. The listener may wear insert plugs, earphones, or listen to sounds played over speakers (called a “soundfield”) while sitting in an acoustically treated booth. Tones will be played at various pitches and intensities. The responses may be measured by:
- Behavioral Observation Audiometry (BOA): measuring responses based on the child’s behavior (eye blinking, eye widening, sucking on a pacifier, etc.)
- Visual Reinforcement Audiometry (VRA): measuring the child’s responses based on a head turn to a screen or light-up box with puppets, or other visual reinforcement
- Conditioned Play Audiometry (CPA): measuring the child’s responses based on a conditioned play response (stacking rings, putting a block in a bucket, etc.)
- Adults and older children usually respond by pushing a button or raising their hand to indicate that they heard the tones
Various measurements will be taken of the listener’s hearing ability, and the results will be marked on the audiogram as follows:
Air Conduction refers to sounds transmitted through the air (soundfield, headphones, inserts). This tests if sounds are audible after going through the outer, middle, and inner ear. Bone Conduction refers to sounds transmitted through a bone oscillator. Those sounds bypass the outer and middle ear and test inner ear (cochlear) functioning alone. People with a conductive hearing loss have difficulty with air conduction testing due to outer or middle ear issues, but they will perform well on bone conduction testing, as they do not have problems with cochlear hearing. People with sensorineural hearing loss will have difficulty hearing tones presented through both media (air and bone conduction). People with mixed hearing loss will have components of both types of hearing loss. (Click these links for more information on parts of the ear and types of hearing loss.)
Masking refers to playing “distraction noise” in the opposite ear while testing hearing loss. It is often used when there is a large mismatch in hearing loss level between the ears, to prevent the ear with greater hearing from “helping” the opposite ear and distorting test results.
Those are just the basics of pure tone audiometry. Stay tuned for future posts about how hearing aids are fit, cochlear implants are mapped, and hearing in noise is tested. Leave questions below!