Week 9 - Lifelong Hearing Flashcards
Scope of Practice - Hearing
Screening tests of hearing and middle ear function
Interpretation of audiograms
Troubleshooting hearing aids and other devices
Information provision and advocacy (helping clients access info and services)
Sound Definition
Movement of a disturbance through an elastic medium without permanent displacement of the particle
Soundwave definition
Physical disturbance in air pressure, arising from a vibrating source
Air molecules compress and rarefy in a pattern, depending on the nature of the source vibrations
Air Conduction
Vibrations travel through the middle ear to the cochlea via air
Bone Conduction
Vibrations travel to the cochlea via the skull bones
Air Conduction - Process
Outer ear:
- Pinna catches sound and funnels it to the EAM
- EAM conducts sound waves to tympanic membrane
Middle ear:
- Tympanic membrane vibrates in response to sound
- Ossicles conduct vibrations to oval window
Bone Conduction - Process
Inner ear:
- Sound vibrates skull bones (usually temporal bone)
- Vibrations of fluid in the inner ear create electric potential to transduce sound waves into neural impulses
Afferent Pathways
Cochlear and vestibular branches of CN VIII join at the internal auditory canal
Afferent impulses travel up to CN VIII, through brainstem to the auditory cortex
- Decussation of impulses at cochlear nucleus
- Direct left-right communication also occurs at superior olivary nucleus (brainstem) and inferior colliculus (midbrain)
CNS Control of the Hearing Process - Auditory Cortex
Superior temporal gyrus
Binaural hearing results from decussation
Primary auditory cortex processes temporal order of sounds, frequency combinations
Secondary and tertiary auditory cortices process language, motor production of language and processing of syntax in Broca’s area, Wernicke’s area processes speech perception
Disabling Hearing Loss in Adults
> 40dB in the better ear
Disabling Hearing Loss in Children
Loss of >30dB in better ear
Grades of Hearing Impairment
No Impairment Slight Impairment Moderate Impairment Severe Impairment Profound Impairment
Grades of Impairment - No Impairment
25dB or better (in better ear)
No/very slight hearing problems
Able to hear whispers
Grades of Impairment - Slight Impairment
26-40dB (in better ear) Able to ear and repeat words spoken in normal voice at 1m Recommendations: - Counselling - Hearing aids may be needed
Grades of Impairment - Moderate Impairment
41-80dB (in better ear)
Able to hear and repeat words spoken in raised voice at 1m
Recommendations:
- Hearing aids used regularly
