Types of Hearing Loss
- Conductive Hearing Loss: Conductive hearing loss occurs when sound is not conducted efficiently through the outer ear canal to the eardrum and the tiny bones (ossicles) of the middle ear. Conductive hearing loss usually involves a reduction in sound level or the ability to hear faint sounds. This type of hearing loss can often (but not always) be corrected medically or surgically. Possible causes of conductive hearing loss may include: fluid in the middle ear from colds/congestion; ear infection (otitis media, otitis externa, Swimmer’s Ear); allergies; poor eustachian tube function; perforated eardrum; impacted earwax (cerumen); presence of a foreign body; absence or malformation of the outer ear, ear canal, or middle ear bones (ossicles); benign tumor.
- Sensorineural Hearing Loss (SNHL):
Sensorineural hearing loss occurs when there is damage to the inner ear (cochlea), or the nerve pathways from the inner ear to the brain. Most of the time, SNHL cannot be medically or surgically corrected. This is the most common type of permanent hearing loss. SNHL reduces the ability to hear sound. Even when speech is loud enough to hear, it may still be unclear or sound muffled. Possible causes of SNHL include: illnesses, genetic syndromes, drugs that are toxic to the ears; hereditary/genetic hearing loss; aging; head trauma; absence or malformation of the inner ear structures or auditory nerve; exposure to loud noise.
- Mixed Hearing Loss: Mixed hearing loss refers to when a conductive hearing loss and sensorineural hearing loss occur simultaneously. For example, there may be damage to the outer or middle ear as well as the inner ear (cochlea) or auditory nerve.
- Auditory Neuropathy Spectrum Disorder (ANSD): Auditory Neuropathy Spectrum Disorder is an auditory disorder in which the neurons in the hearing nerve and brain stem do not "fire" together in an appropriate manner. As a result, a person with with ANSD may have difficulty distinguishing one sound from another and/or trouble understanding speech clearly. In some cases, ANSD causes only mild hearing difficulties and/or is only a problem in noisy situations. However, in many cases, there are significant hearing difficulties and amplification of some type is required. The causes of ANSD are unknown, however children who are born prematurely, require extended oxygen support, or have a family history of the condition are at a higher risk. Symptoms can develop at any age, however most children with ANSD are born with it and are diagnosed within the first few months of life.
- Auditory Processing difficulties can impact language development, speech, learning, reading, and success in school. The effects vary based on the amount of auditory processing difficulty and whether problems other than auditory processing are present. Auditory processing problems can exist when no hearing loss is present, or exist along with hearing loss (conductive, sensorineural, or mixed). When hearing loss is present, it may not be possible to determine which difficulties are caused by auditory processing disorder and which are caused by the hearing loss or other factors. A comprehensive auditory processing evaluation is required to determine if a child has an auditory processing disorder.
Degrees of Hearing Loss
The outcome of a hearing evaluation is graphed on a chart called an audiogram, which records the softest sounds your child heard in each ear and/or in a soundfield during the behavioral hearing test (hearing thresholds). Loudness is measured in decibels hearing level (dBHL) and is represented on the vertical axis of the audiogram, from 0 dBHL (very soft) to 110 dBHL (very loud). Frequency (or pitch) is measured in Hertz (Hz.) and is represented on the horizontal axis of the audiogram, from 250Hz (very low, e.g. fog horn) to 8000 Hz (very high, e.g. whistle). Hearing test results are not typically given in percentage, but instead in degrees. The degree of hearing loss is based on the recorded audiometric thresholds, and ranges in severity from mild to profound.
Mild Hearing Loss:
Thresholds between 25-40 dBHL
. Difficulty will often occur for soft speech and listening in background noise; in quiet, a mild hearing loss may be manageable for adults, however children can still experience impacted language development.
Moderate Hearing Loss:
Thresholds between 41-55 dBHL
. Difficulty hearing conversations, especially while in background noise. Speech must be loud to be understood. The TV, radio, etc., often needs to be turned to higher volume levels to be heard clearly. For children, speech, language, vocabulary and comprehension are likely to be affected.
Moderately-severe Hearing Loss:
Thresholds between 56-70 dBHL
. Speech must be loud to be understood. Volume and clarity of speech is significantly reduced and the most difficulty will occur in groups. For children, speech, language, vocabulary and comprehension are likely to be affected.
Severe Hearing Loss:
Thresholds between 71-90 dB
. Normal conversation is not audible, and loud speech is difficult to hear or understand. May be able to identify environmental sounds, and may be able to discriminate vowels, but not consonants. Speech, language, vocabulary and comprehension are significantly impacted. Visual imput such as sign language is beneficial, even if amplification is used.
Profound Hearing Loss:
Thresholds 91 dB
and higher. Only very loud sounds may be heard, and even amplified speech may be soft and may not be understood. Speech, language, vocabulary and comprehension are significantly impacted. Visual input such as sign language is often relied upon, even if amplification is used.
The Speech Banana Audiogram
The audiogram below is is a tool that can be used to understand what we are hearing or not hearing (based on different pitches within the environment). The sounds that we use to produce speech in conversation have frequencies and decibels. The most typical frequency and decibel for each speech sound is graphed on the audiogram below to provide information about what sounds can be heard at specific degrees of hearing loss. A child that can hear the sounds of speech will have a much easier time imitating, understanding and learning spoken language when compared to that of a child who can not hear all of the sounds of speech.
The “Speech Banana” is a term used to describe the area where the phonemes, or sounds of human speech, appear on an audiogram. When the phonemes are plotted out on the audiogram they take the shape of a banana, therefore audiologists and other speech professionals refer to that area as the speech banana. While many other sounds fall outside of the speech banana, audiologists are most concerned with the frequencies within the speech banana because a hearing loss in those frequencies can affect a child's ability to learn language.
back to top