Types of Hearing Loss

2014 / 08 / 15  |  
Prevent hearing loss

If you discover that you may have a hearing loss, Erdo’s hearing test provides you with an audiogram to further understand the cause of your hearing loss. Different audiogram configurations represent different types of hearing loss.

An audiogram may seem fairly complicated at first glance, but it's not hard to figure it out. To put it simply, what you see on your audiogram indicates how loud the sound needs to be for you to hear it at frequencies ranging from 500-8,000 Hz, and it's referred to as your “hearing threshold” (the minimum sound level you can hear). The greater the spread is from your hearing threshold to 20 db HL, the more severe your hearing loss is at that frequency.

On each of Erdo's audiogram, the colored area represents the sounds you can hear. The larger the colored area is, the greater your hearing is. The edge of the colored area is your hearing threshold.

Indicated by this audiogram, we can see that the person's hearing threshold at each frequency tested exceeds 20 dB HL. It means that he/she is having a hearing loss at each frequency, especially at high frequencies.

Based on audiogram configurations, there are mainly three types of hearing loss: falling, rising, and flat. Although other types of configurations do appear occasionally, you should still be extra careful about the possibility of having special diseases when your audiogram shows either of the following configurations: asymmetric loss, cookie-bite loss (where the curve is higher at both ends and lower in the middle), and reverse cookie-bite loss (where the curve is lower at both ends and higher in the middle).

(1) The falling configuration:When the curve is higher on the left and lower on the right, it means the hearing loss mostly occurs at higher frequencies. Possible causes include presbycusis, noise-induced hearing loss, and so on.

(2) The rising configuration:When the curve is lower on the left and higher on the right, it means the hearing loss mostly occurs at lower frequencies. Such an audiogram could come from people suffering from impacted cerumen or Ménière's disease.

(3) The flat configuration:It occurs when the hearing loss is roughly the same at both low and high frequencies.

(4) The asymmetric hearing loss:It occurs when both ears have unequal hearing. In addition, the difference between the hearing thresholds of the ears at any frequency is larger than 15 dB.

(5) The high frequency and low frequency hearing loss:The configuration looks like a hill where the hearing loss is much severe at low and high frequencies. The spread from the hearing threshold at low and high frequencies to that at mid frequencies could be more than 20 dB.

(6) The mid frequency hearing loss:The configuration looks like a valley where the hearing loss is much severe at mid frequencies. The spread from the hearing threshold at low and high frequencies to that at mid frequencies could be more than 20 dB.

Based on the impacted area of ears, hearing loss is also classified into three main types : conductive, sensorineural, and mixed hearing loss.

(1) The conductive hearing loss. (Sounds can only be heard at a higher volume.)

It occurs when disorders of the outer or middle ear decrease the sound transmission efficiency. Such disorders include impacted cerumen, tympanosclerosis, otitis media with effusion, and so on. With adequate sound volume, patients normally can hear the sounds clearly because the inner hair cells and the auditory nerve still function well. Some conductive hearing loss such as perforations of the tympanic membrane and otosclerosis can be treated with surgery.

(2) The sensorineural hearing loss. (The intelligibility of sounds is affected even despite the higher volume.)

The inability to transfer sounds to neural signals and the neuron's failure to transmit messages to the brain could be the results of affected inner hair cells or impaired auditory nerve. Even with enough sound volume, the sound intelligibility in the patient can still be compromised.

Sensorineural hearing loss can be further categorized as sensory hearing loss and neural hearing loss. Sensory hearing loss is the result of impaired hair cells. The different hair cells inside the cochlea either regulate sounds or transfer sounds to neural signals. However, hair cells are easily damaged by ear-related disorders, noises, drug use, cardiovascular diseases, aging, and so on. Neural hearing loss occurs when the nerve transmitting neural signals is damaged, resulting in the poor transmission of neural signals. Under such circumstances, patients may often hear sounds but in an unclear manner.

(3) The mixed hearing loss. (It occurs concurrently at the outer ear or the middle ear, and inner ear or auditory nerve.)

Simply put, mixed hearing loss is a combination of conductive hearing loss and sensorineural hearing loss.

Now that you know the types of hearing loss, are you curious about what your audiogram looks like? You can find out more about your hearing if you check out the audiogram configurations and diseases in “Disease 101” and go through the “Hearing-Related Diseases.”

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