Hearing Aids

Bernycia Askew

Who they’re for Hearing Aids are usually best for people who have a mild-

moderate hearing loss.

They are often benefit those who have contracted noise induced hearing loss with age and have a high frequency loss

While those who can be considered legally deaf can acquire hearing aids, the will usually suffer from a extreme sensori-neural hearing loss and would benefit more from a cochlear implant.

Often recommended to people when there is noticeable difficulty understanding speech.

Pure Tone Testing Air Conduction- used to measure the ability of hearing

from the outer and middle ear. Done with headphones

place over Outer Ear or inserted into the ear canal.

Bone conduction- Measure of inner ear through bone

conduction. Tone sent directly through temporal bone to

the inner ear.

Hearing Testing Some of the basic measurements when fitting a person for a hearing aid

Puretone Average (PTA)-After pure tone air conduction responses have been recorded for

each ear, the responses at 500 Hz, 1000Hz and 2000 Hz are averaged and recorded in the

summary chart of the audiogram. Measured in decibels (dB).

Most Comfortable Listening Level

Uncomfortable Listening Level

Speech Recognition Threshold (SRT)- The Speech Recognition Threshold (SRT) is

measured in decibels (dB), Two-syllable words, called Spondee Words, are presented to the

client. The SRT is defined as the lowest hearing threshold level at which 50% of a list of

Spondee Words is correctly identified for each ear.

Word Discrimination score (WD)- is based on the percentage of words correctly understood

when presented at MCL or at a normal conversational speech level (40dB-60dB).

Types of Hearing loss Conductive- mechanical issues in outer or middle ear

Sensorineural hearing loss- Damage to the cochlea or

auditory nerve, permanent.

Mixed Hearing loss- a combination of conductive and

Sensorineural hearing loss.

Hearing Aid Parts Microphone- picks up sound from the environment

and converts it into an electrical signal, which it sends

to the amplifier

An Amplifier- increases the volume of the sound and

sends it to the receiver.

A receiver/speaker- changes the electrical signal back

into sound and sends it into the ear. Then those

impulses are sent to the brain.

A battery-provides power to the hearing aid.

Digital vs. Analog

Analog hearing aids amplify sounds -- the trouble is

they amplify all sounds equally. Conversational speech

is obstructed by other “back ground noise” (like the

television, or a vaccumm cleaner) Some analog

hearing aids are programmable, meaning that they can

hold separate settings for different listening situations.

You can "change the channel" to adjust certain sounds

louder or softer, depending on your preferences and

hearing loss. They aren't as sensitive as digital hearing

aids.

Styles Behind the Ear

In the Ear

In the canal

Completely in the canal

Hearing aid size can correlate to the amount of loss a person has. Smaller hearing aids have smaller batteries, and are better for those with a mild/moderate loss whereas bigger aids are for more severe cases because they have more power to amplify sound.

Bone conduction HA External bone-conduction hearing aids function by transmitting sound waves through the bone

to the ossicles of the middle ear. New technology have also allowed for the BAHA Implants that

Allow vibrations to go directly to the Inner ear.

Air-conduction hearing aids require the use of ear molds, which may be problematic in patients

with chronic middle ear and ear canal infections or an ear canal that cannot accommodate an

ear mold. bone-conduction hearing aids may be an alternative.

A titanium post is surgically attached to a bone behind the ear. The sound processor attaches to

the post and transmits sound vibrations through external abutment to the titanium implant. The

implant vibrates in the skull and inner ear, stimulating the nerve fibers of the inner ear and

allowing the individual to hear.

Some issues…. Feedback- a squealing/whistling caused by sound

(particularly high frequency sound) leaking and being

amplified again, may be a problem for severe hearing

losses.

To High of a Gain- The ideal Gain for a person is ½ to

1/3. If the fitting of the hearing aid doesn’t suit the

hearing loss, or if there is too much amplification, the

hearing aid can actually cause noise induced hearing

loss.