Understanding Hearing Loss – Part 1
In my own practice, I often find myself counseling families about hearing loss and how it can affect speech and language development. Hearing loss can be tricky and its effects on development aren’t necessarily obvious, but hearing plays a huge part in your child meeting many developmental milestones. It’s important to know about hearing and how hearing loss can present itself…especially in the mild, non-obvious cases.
First, let’s make sure we are on the same page and dispel and simplify some common misconceptions about hearing loss.
There is no such thing as a percent loss when it comes to hearing. There are two important things to consider – frequency and decibels. All of our speech sounds occur at different frequencies (Hz); it’s what many people consider to be the “pitch” of the sound. You can think of decibels (dB HL) as the “volume” or “loudness level.” When you participate in a hearing test, your evaluator is trying to determine at what loudness level (dB HL) is needed for you to hear each frequency (Hz). Normal hearing for adults falls between 0-15 dB HL across all frequencies (Hz).
For example, the sound /s/ is about 6000 Hz. Your audiologist will test to see if you can hear 6000 Hz sounds in the 0-15 dB HL range. If you hear the sound and respond within that range, your hearing is likely normal at 600 Hz. If you don’t hear the sound, the evaluator may increase the “loudness level” (dB HL) to see what how loud the input needs to be in order for you to respond to that sound. Thus, if you hear the sound at 40 decibels, then you may have mild-moderate hearing loss because it makes extra “volume” for you to hear that sound at that particular frequency.
So you may hear most frequencies in the normal range, but you start to dip at 6000 Hz and at that level 40 dB HL is needed for you to respond to that sound. You would then describe your hearing by saying you have a mild-moderate hearing loss at 6000 Hz. Hearing loss is typically described as severities (e.g., mild, moderate, severe, etc.) for each sound frequency tested. It is not described as a percentage.
Things to keep in mind- normal hearing ranges vary for children and adults. The information here is an over simplification of how hearing is tested. Ask your audiologist or doctor if you have additional questions about the results of your (or your child’s) hearing test
Here is a picture of a “speech banana.” It shows the different frequency ranges of various sounds on the x-axis. The “loudness level” (dB HL) is shown on the y-axis along with pictures that show objects that make sounds with that same “loudness level.” For example, 120 dB HL is about as loud as an airplane. If a 120 dB HL (about as loud as an airplane) is needed for you to hear a sound, that constitutes a significant hearing loss.