GENERAL:

Audiograms are used to diagnose and monitor hear loss.Audiograms are produced by plot the thresholds in ~ which a patient have the right to hear various frequencies.Hearing loss have the right to be divided into two categories: conductive or sensorineural. The outcomes of an audiogram can assist direct medical and also surgical interventions to enhance and/or preserve hearing function.

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BACKGROUND INFORMATION:

INTENSITY: 

Intensity of sound is measured in decibels (dB) which deserve to be believed of together the ‘loudness" the the sound.The decibel range is logarithmic (based ~ above a factor of 10):An boost of 10 dB means a 10-fold rise in sound intensity.An boost of 20 dB method the sound is 100-fold an ext intense.Standard audiograms test between 0 and also 110dB.For reference, typical conversation is roughly 60 dB

Common sounds and their intensity (dB)

Near-total silence

0 dB

Lawnmower

90 dB

Whispering

15 dB

Car Horn

110 dB

Refrigerator Hum

40 dB

Jackhammer

120 dB

Normal Conversation

60 dB

Gun shoot or Firework

140 dB

Vacuum Cleaner

70 dB

Jet Takeoff

150 dB

FREQUENCY:

Frequency is measure in Hertz (Hz), i beg your pardon is frequently thought of as the “pitch” of the sound.The mean human have the right to hear in between 20 and also 20,000 Hz Audiograms commonly test frequencies in between 250Hz and also 8000Hz.Human speech usually falls in between 250Hz and also 6000Hz.

AUDIOMETRIC TESTING: 

During testing, the audiometer delivers assorted “pure tone” sound at specific frequencies and also intensities, from short to high.The patient’s capacity to hear these tones is plotted top top a graph to create an audiogram.In kids testing different according to age:Evoked otoacoustic emissions (EOAE): test duty of outer hair cells, often used as a child hearing screenAuditory brainstem an answer (ABR): use electrodes come monitor mind activity solution to sound stimulus, can be excellent at any type of age yet will often need to it is in sedated after 6moBehavioral observation audiometry (BOA)(0 come 5 mo): observes child an answer to sound stimulus. Does not assess lateralityVisual combine audiometry (VRA) (6mo to 2yo): son turns to intuitive cue in response to sound stimulusConditioned beat audiometry (CPA)(2yo come 5yo): boy interacts with toy or object in solution to sound stimulus. Can assess laterality.Conventional pure-tone audiometry (5yo+): increasing hand in response to sound stimulus.

DEGREES OF hearing LOSS

Degree of hearing Loss

Thresholds (dB)

Description 

Normal

0-25 Adult (0-15 infant)

Normal Hearing

Mild

20-40

Unable to hear soft sounds. Can hear conversations in a quiet setting but mine have an obstacle in noisy environments

Moderate

41-55

Has an obstacle hearing part quieter conversations.

Moderate Severe

56-70

Has difficulty hearing a typical conversation. Might lip-read or use hearing aids to help with communication

Severe

71-90

Can recognize speech only if the speaker is in close proximity

Profound

>90

Generally, cannot understand speech. Unable to hear "loud" stimuli such together lawn mowers or pass cars

TYPES OF hearing LOSS:

Hearing loss have the right to be split into 2 types: conductivesensorineuralConductive and sensorineural hearing losses can happen alone or in combination.A combination of conductive and also sensorineural hearing loss is referred to as a “mixed hearing loss.”

CONDUCTIVE hear LOSS (CHL):

A conductive hearing ns occurs as soon as sound native the atmosphere is can not to be ‘conducted’ come the frameworks of the within ear.Differential diagnosis includes:Cerumen impaction,Perforated tympanic membraneFluid in the middle ear spaceOtosclerosisConductive hearing losses are more likely to be correctable through surgical treatment than sensorineural losses. Air conduction describes conduction with the whole outer ear mechanism: including auricle, outside ear canal, tympanic membrane and ossicles/middle ear. Bone conduction describes soudn vibration transmitted come the inside ear through the skull.Conductive loss have the right to be assessed v the Rinne and also Weber testWeber: location the tuning fork in the midline and also determine which ear its heard louder. Normal: heard equally according to in both ears (also equal in symmetric bilateral hear loss). Unilateral conductive hearing loss: lateralize to affected ear. Unilateral sensorineural hear loss: lateralize come contralateral ear.Rinne: location the tuning fork in prior of the ear and over the mastoid and determine in which place it is heard louder. Normal: wait conduction > bone conduction (positive Rinne). Conductive listening loss: bone conduction > wait conduction (negative Rinne). Sensorineural hearing loss: air conduction > bone conduction (positive Rinne).A flipped 256 Hz fork synchronizes to a 15 dB hear loss. Whispered voice is around 20 dB and normal spoken voice is 50 come 60 dB.

SENSORINEURAL HEARING lose (SNHL): 

Sensorineural hearing ns occurs as soon as there is damage to the structures of the inside ear or concerned pathways in between the ear and also brain SNHL is the many common type of irreversible hearing loss. The many common cause of SNHL in the United says is chronic noise exposure. SNHL is frequently not together amenable to surgical intervention contrasted to conductive listening loss.Differential Diagnosis because that SNHL:Infectious: meningitis, mumps, measles, syphilis, etc. AutoimmuneOtotoxic Medications: aminoglycosides, platinum chemotherapeutics, methotrexate, furosemide, aspirin, etc. Familial PresbycusisHead trauma: temporal bone fracturesCongenital malformations the the within ear structures Noise-induced listening loss Neoplastic: acoustic neuroma or meningioma

AUDIOGRAM:

The hear test outcomes are plotted on a graph v the y-axis representing listening threshold and the x-axis representing frequency.The best ear is usually plotted v a O and the left ear through a X.Bone conduction is likewise plotted (to permit for differentiation of conductive and also SNHL). The appropriate ear is plotted as .Common measures:Threshold = the shortest level that sound that have the right to be heard 50% of the time.Speech reception threshold (SRT) = Softest strongness bisyllabic spondee (balanced syllable) words can be recurring 50% the the timeWord acknowledgment score = % of native discerned in ~ thresholdSpeech discrimination = % single syllabic native identified and also repeated in ~ suprathreshold levels (generally 30 dB over SRT)Acoustic reflex = muscle convulsion in center ear in response to high intensity economic stimulation (contralateral and also ipsilateral reflexes tested)Tympanometry = assessing exterior auditory canal volume and also tympanic membrane mobility v air pressure.Type A: normalType B “flat”: limited mobility, fluid or TM damageType C: an unfavorable pressure native retractionPatients will frequently ask what their “percentage of listening loss” is. Over there is no evidence-based formula to transform the logarithmic dB range to a percentage of hearing loss with any kind of meaning.There IS a formula to calculation percent handicap for handicap pension eligibility:Take the thresholds for four frequencies (500,1000,2000,3000) for each ear and also average themIncrease through 1.5% because that each dB over 25dB because that each earMultiply the better ear through 5 (to weight it more heavily). Include that number through the worse ear and also divide through 6 to acquire your listening handicap.This formula has plenty of problems and is not the percent listening loss

CHRONIC NOISE EXPOSURE: 

Noise-Induced Hearing loss (NIHL) typically demonstrates a “knoch” on the audiogram at 4000k.Sounds about 85 dB for prolonged periods that time can reason hearing lossIf you need to raise her voice to it is in heard, (normal conversation is roughly 60dB) you space most likely in an environment with at least 80 dB of noise. 

REFERENCES/SUGGESTED READING:

How to review an Audiogram and Determine degrees of hearing Loss. The national Hearing Test. Http://www.nationalhearingtest.org/wordpress/?p=786. Accessed in march 13, 2019.

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Walker JJ, Cleveland LM, Davis JL, Seales JS. Audiometry Screening and Interpretation. American household Physician. Https://www.aafp.org/afp/2013/0101/p41.html. Published January 1, 2013. Accessed march 13, 2019.