This is the second part in my series of posts which will be/is about hearing loss in general, but also my hearing loss in particular. In my last post, I mentioned a Youtube video which explains several things people with mild hearing loss deal with on a daily basis. If you want to know more about that, see the first post in this series, “Hearing Loss Part 1”.
Most of us know that deaf and hard of hearing people exist. You may have met a deaf person before, and it’s highly possible that you’ve met a hard of hearing person– this person may be related to you, such as a grandparent, an uncle, or even a brother or sister. However, that doesn’t mean we know the different terms that go along with audiology (the study of hearing, balance, etc… basically, stuff that has to do with the ears), and it doesn’t mean we really understand what it means to be deaf or HOH. In this part of the series, I want to explain some things about hearing loss. It’s too much to cover in one singular post. If you have a hearing loss and are reading this, and you see something that is incorrect, feel free to correct me. I don’t want to be sharing inaccurate info.
First of all, there is the level of hearing loss a person has. There are 6 different main hearing levels for adults: normal, mild loss, moderate loss, moderately-severe loss, severe loss, and profound. There is one more level for young children, slight loss. It is included because of possible effects on language development. This level does not count for adults because they are no longer in the “I’m just learning to talk” stage of their lives.
When someone has a full hearing exam (not a hearing screening, that’s much simpler than a full hearing check), the level of sound they are able to hear is graphed on an audiogram. On the left side of the audiogram are the decibel numbers, going from the top down. These numbers show how loud the sounds are. So, a sound that is 28 decibels is a lot louder than a sound that is 5 decibels. A whisper is said to be at somewhere around 20-30 decibels, general conversation is between 55 and 65 decibels, and sounds start to be dangerous to hearing at around 85 or 90 decibels. Along the top of the audiogram are the frequency numbers, which are measured in hertz. These indicate how high or low the sound is, whether it’s really high pitched like a fire alarm, flute, or bird chirping– or if it’s lower pitched like a tuba or a bass singer.
I could go into detail and make this part really complicated, but I’d rather give the basic explanation. When you take the hearing test, you put on either a pair of headphones or a pair of something similar to earbuds (three of the four times I’ve gone, it’s been a pair of headphones). Then, specific tones are played into each ear at different frequencies (such as 250 Hz and 4000 Hz), one ear at a time, and you respond if you hear something. Whenever I’ve gone for a hearing test, they generally start out nice and loud, and then make it quieter and quieter until I can’t hear the tone anymore. Most of the hearing test involves different variations of what I just described– for example, sometimes they will play static into one ear while testing beeps in the other, or they’ll test your bone conduction instead of air conduction (which I may or may not discuss in a later post). Then they take the quietest sounds you heard, and graph them on the audiogram. This shows your hearing threshold, or the softest sound you were able to hear at each frequency. I know even this may sound complicated, but believe me, it’s a lot simpler than explaining in full what is done in the hearing test and why. Going back to the levels of hearing loss, the main categories are described as follows:
- Normal hearing goes from -10 dB (10 decibels above the zero, which is better than average hearing) to 15 dB (decibels) below the zero
- Slight hearing loss-which generally applies to children- is from 16 dB to 24 dB
- Mild hearing loss is 25 dB to 39 or dB
- Moderate loss is 40 or 41 dB to 55 dB
- Moderately-severe is 56 dB to 69 dB
- Severe is 70 to 89 dB
- Profound is anything 90 decibels and above.
Now, it’s all fine and dandy that I’ve given you a bunch of numbers, but what do they actually mean?
When a person hears a sound at a certain decibel level and that sound increases by 10 decibels, the person perceives the sound to be twice as loud; if it increases by 20 dB, then it sounds four times as loud to that person. There is a difference between the actual strength of the sound versus the perception of the strength of the sound, but I don’t know how all that works, so I’m not going to even try to go into that. But basically, a sound at 15 dB sounds twice as loud as if it were 5 dB, and a sound at 25 dB sounds 4 times louder than a sound at 5 dB. Simple, right?
*I make no claim to being a professional audiologist who officially knows all this stuff. The next two paragraphs are purely speculation based on my interpretation of what I have learned about this kind of thing. Please look these things up yourself, and don’t automatically assume that I am correct.*
For a person with perfect hearing, the quietest sound audible is 0 dB (zero decibels just means it’s the quietest sound that’s typically audible to the human ear. There are quieter sounds out there). For a person with a 30 decibel hearing loss to whom the softest sound audible (the hearing threshold) is 30 dB, a sound that is at 40 dB is perceived to be the same loudness as a person with perfect hearing perceives a 10dB sound.
Now, if Person A has hearing thresholds between 5 and 10 dB all across the audiogram (which is considered normal hearing), but Person B has a mild hearing loss and his hearing thresholds are between 25 and 30 dB all across the board. Both of these people listen to Person C, who is talking to them at a normal conversation level, between 55 and 60 dB. Both of them can hear him, but there is a full 20 dB difference in their hearing ability– A hears C speak 4 times louder than Person B hears. This is ignoring the fact that several sounds made in the English language become difficult to hear or even inaudible once this level of hearing loss is reached, i.e. the “v” and “z” sounds in the lower frequencies, and the “s”, “th”, and “sh” sounds in the higher frequencies. This loss of consonants makes speech even harder to understand. That is why even a mild hearing loss can have a strong effect on a person’s ability to understand speech, and why audiologists are concerned when a child who is still developing speech is found to have a hearing loss.
If you made it this far, thanks for taking the time to read the whole post. It took forever to write. Please leave a comment below, and have a great day! God bless!