Audiology

Audiology is the science of hearing, balance, and related disorders.
Audiologists are healthcare professionals who provide patient-centered care in the prevention, identification, diagnosis, and evidence-based treatment of hearing, balance, and other auditory disorders for people of all ages.
The ear can be divided into three parts leading up to the brain – the outer ear, middle ear and the inner ear.
  • The outer ear consists of the ear canal and eardrum. Sound travels down the ear canal, striking the eardrum and causing it to vibrate.
  • The middle ear is a space behind the eardrum that contains three small bones called ossicles. This chain of tiny bones is connected to the eardrum at one end and to an opening to the inner ear at the other end. Vibrations from the eardrum cause the ossicles to vibrate which, in turn, creates movement of the fluid in the inner ear.
  • Movement of the fluid in the inner ear, or cochlea, causes changes in tiny structures called hair cells. This movement of the hair cells sends electric signals from the inner ear up the auditory nerve (also known as the hearing nerve) to the brain.
  • The brain then interprets these electrical signals as sound.


    Compiled from www.asha.org, “About Audiology”
    There are broadly 3 types of hearing losses

    Conductive - A conductive hearing loss happens when sounds cannot get through the outer and middle ear.
    A conductive hearing loss can be caused by the following:

    • Fluid in your middle ear from colds or allergies.
    • Ear infection.
    • Poor Eustachian tube function.
    • A hole in your eardrum.
    • Deformed pinna or ear canal or a problem with the bones in their middle ear

    Sensorineural – A Sensorineural hearing loss happens from inner ear damage (cochear) or if there is a problem in the nerve pathways leading from the inner ear to the brain (retrocochlear) or if there is a problem in the auditory areas in the brain (central).

    A sensorineural hearing loss can be caused by the following:

    • Illnesses.
    • Medicines/drugs that are toxic to hearing.
    • Aging.
    • Head injury.
    • Malformation of the inner ear (cochlea).
    • Exposure to loud noises or explosions.
    • Tumor of the auditory nerve.

    Mixed - Sometimes, a conductive hearing loss happens at the same time as a sensorineural hearing loss. This means that there may be damage in the outer or middle ear and in the inner ear or nerve pathway to the brain. This is a mixed hearing loss.

    Other terms describing a hearing loss:

    • High-frequency versus low-frequency. Whether high-pitched or low-pitched sounds are heard better.
    • Bilateral versus unilateral. Bilateral means hearing loss in both ears. Unilateral means hearing loss in one ear.
    • Symmetrical versus asymmetrical. Symmetrical means the severity and shape of hearing loss are the same in each ear. Asymmetrical means each ear has a different severity and shape.
    • Progressive versus sudden hearing loss. Progressive means that hearing loss becomes worse over time. Sudden means hearing loss that happens quickly. You should see your doctor right away if you have a sudden hearing loss.
    • Fluctuating versus stable hearing loss. Fluctuating means hearing loss that changes over time. It sometimes gets better, sometimes gets worse. Stable means that your hearing loss has stayed the same.

    Complied from www.asha.org “configurations of hearing loss”
    Degree of hearing loss is measured in dBHL and it tells us how loud sounds need to be for a person to hear them.
    Degree of Hearing Loss
    Hearing loss range (dBHL)
    Normal
    -10 to 15
    Minimal
    16 to 25
    Mild
    26 to 40
    Moderate
    41 to 55
    Moderately-Severe
    56 to 70
    Severe
    71 to 90
    Profound
    91+
    Hearing aids
    A hearing aid is a small battery-powered electronic device designed to improve hearing for individuals who have a hearing loss. They can be worn in the ear or behind the ear. They help the individual hear better in quiet as well as noisy environments.

    BAHA
    Bone-anchored hearing aid (BAHA) is a type of hearing aid primarily suited for people who have a conductive hearing losses, unilateral hearing loss, and people with mixed hearing losses who cannot otherwise wear 'in the ear' or 'behind the ear' hearing aids. Their placement involves invasive surgery. BAHA stimulates the cochlea by transmitting the sound waves through the bones of the skull, thereby bypassing the outer and middle ear. Once the cochlea receives the sound signals, the information is converted into neural signals and transferred to the brain, where it is perceived as sound.

    Cochlear implants
    A cochlear implant (CI) is a surgically implanted electronic device that replaces the function of the damaged inner ear. Cochlear implants do the work of damaged parts of the inner ear (cochlea) to provide sound signals to the brain.
    A cochlear implant can help to provide a sense of sound to a person who is profoundly deaf or severely hard-of-hearing. The implant consists of an external portion that sits behind the ear and a second portion that is surgically placed under the skin. The implant picks up sound and digitizes it, and then converts that digitized sound into electrical signals, which are transmitted to electrodes embedded in the cochlea. The electrodes electrically stimulate the cochlear nerve, causing it to send signals to the brain.