Diagnostic Hearing Evaluations
Tympanometry is a test conducted by audiologists to check how well the middle ear system is working. A soft flexible probe is placed into the ear canal and measures the eardrum’s overall responsiveness to sound. Tympanometry is not a hearing test; instead, it measures how sound travels through the middle ear.
Tympanometry is an excellent way to determine if hearing loss is due to nerve damage or inner ear problems. A person’s tympanogram can tell a lot about their ability the health of their middle ear.
Common problems that can be diagnosed with tympanometry include a blockage of the Eustachian tube, eardrum perforation, myringosclerosis, otosclerosis or ossicular chain discontinuity, among others.
The cochlea is the sensory organ in the inner ear that converts sound waves into nerve impulses that can be recognized by the brain as sound. The cochlea also does something rather interesting in people with healthy hearing; it makes a soft sound of its own when it is functioning properly. An audiologist can detect this sound through a process called otoacoustic emissions testing.
These emissions can be painlessly measured through a tiny microphone placed directly into the ear canal. The audiologist presents a tone to the eardrum and attempts to detect the cochlea’s response. If the client has moderate to severe hearing loss, the cochlea will not produce otoacoustic emissions.
Otoacoustic emissions testing is an excellent tool for determining how well a newborn baby can hear, since it does not require any communication. The presence of otoacoustic emissions indicates that the cochlea’s hair cells are responding to sound (i.e., they are working). It is also useful for diagnosing “nerve deafness.”
Pure Tone Testing
Pure tone testing for hearing loss is the gold standard for establishing the exact range of hearing ability or hearing loss. Pure tone testing determines hearing acuity, or the quietest sound a person can hear.
The client is presented with sounds in the right, left, or both ears through earphones. When the client hears a tone, he or she signals when the audiologist. Only one tone is presented at a time, with fading levels of volume at each successive presentation until the client can no longer hear the tone.
A person’s hearing acuity may be better or worse at different frequencies. For example, a person may be able to hear high frequency sounds at low volumes, but is unable to hear low frequency sounds at moderate volumes. Pure tone testing accurately measures hearing across the frequencies of human hearing.
Speech in Noise Testing
People with sensorineural hearing loss (“nerve deafness”) often lose the ability to discriminate human speech from background noise. Speech in noise testing is a way to evaluate how well someone can understand simple words or numbers presented in the midst of varying levels of noise. Since understanding speech over noisy backgrounds mimics circumstances commonly experienced in real life, it is more “realistic” than pure tone testing. For this reason, most audiologists recommend speech in noise testing as part of routine hearing aid evaluation testing protocols.
Speech in noise testing is non-invasive. The client is presented with pre-recorded sentences or phrases within different levels and types of background noise, such as other voices, environmental noise, or machine-generated noise. The more spoken words someone can correctly identify, the better her speech in noise hearing is.
Word Recognition Testing
Word recognition testing determines a client’s ability to recognize words that sound alike (i.e., phonemes). It tests the client’s best ability to recognize speech under ideal conditions.
In word recognition testing, the client is presented with recorded audio containing single syllable words, which she attempts to identify. The test takes place in an audiologist’s office in less than 10 minutes.
Before a person receives a hearing aid, word recognition testing determines the best, unassisted speech recognition a person can achieve. After a hearing aid is placed and fitted, the test is repeated so that adjustments can be made to the hearing device, ensuring optimal performance.