Audiogram

Description:

The audiologic evaluation is a behavioral hearing assessment that can be broken down into three primary components: Pure Tone testing (air and bone conduction), Speech Reception Thresholds (SRT), and Speech Discrimination testing.  All tests should be done by an Audiologist in a sound chamber, which meets or exceeds ANSI 1969 standards.

Pure Tone Testing
This test involves presenting pure tone stimuli to the patient while first wearing head phones, and later utilizing a bone vibrator.  Frequencies tested include half octave intervals from 250-8KHz.  Stimulus intensity is varied in 5dB increments, and the patient determines the threshold by identifying the presence of the stimulus two out of three presentations at a given level.

Speech Reception Thresholds
Spondaic words (e.g. hotdog, baseball, cowboy, etc.) are presented at varying intensity levels, until the patient is able to repeat only 50% of the words presented. If the patient understands the test process, and is cooperating with the procedure, SRTs will approximate the average of pure tone results for the frequencies 500, 1000, and 2000 Hz.

Speech Discrimination Testing
Measures the speech recognition or understanding.  Phonetically balanced and single syllable words (approximating phoneme representation in the native language) are presented at a subjectively comfortable level, which is typically 40dB above the measured SRT.  A percent correct is calculated from the patient’s responses.   Although this test implies an estimate of speech understanding, its primary utility is in test re-test comparisons.  Changes of 12% or more are considered significant and should be investigated.

Indications:

Any patient at risk for hearing loss, or presenting symptoms of tinnitus, vertigo, or aural fullness should be assessed.  In addition, any patient with a history of noise exposure (military, industrial, or recreational), middle ear pathology, or familial hearing loss.

Significant Findings:

Normal Hearing is defined as pure tone thresholds of 25dBHL or better for the frequencies 250-8000Hz with normal speech discrimination ability.

Sensorineural Hearing Loss is defined as pure tone thresholds below 25dBHL for one or more frequencies, where air conduction and bone conduction thresholds are consistent.  The specific site of lesion is typically cochlear or retrocochlear. This category represents approximately 97% of adult hearing impairment.  The impact of the hearing problem is dependent upon degree of loss, number of frequencies affected, and speech discrimination ability. Hearing losses of this nature are typically not medically treatable, and depending on configuration, may require rehabilitation in the form of hearing instruments.  Please consult with the Audiologist regarding specific patient needs.

Conductive Hearing Loss is defined as air conduction pure tone thresholds below 25dBHL for one or more frequencies, where bone conduction thresholds remain within the normal range.  The specific site of lesion is typically lateral to the cochlea (e.g. otosclerosis, Otitis media, middle ear effusion, congenital atresia, etc.).  When detected, an otologic evaluation is indicated to evaluate etiology and potential medical or surgical intervention.

Mixed Hearing Loss is defined as a combination of both conductive and sensorineural hearing loss.

Suggestions:

As with vision or dental, prevention and early intervention is the best approach toward detecting and treating hearing problems.  We recommend universal screening of newborns, and annual hearing tests for adults over the age of 40.  Many physicians are also incorporating hearing screening or inventories into their routine physical examinations.  If you would like more information about these options, please contact one of our audiologists today at 425-899-5050.