hearing tests

 
What to Expect at your First Hearing Test or Audiological Assessment
 
Case History

A case history is obtained in order for the audiologist to understand the history of the patient’s overall hearing health. Some questions on the intake might leave the patient questioning why the audiologist is interested in certain aspects of their overall health, such as whether or not a patient has diabetes. The questions are relevant as there are many medications and ailments that can affect one’s hearing or might have affected it in the past, which is why the audiologist collects this information. The audiologist will also likely try and obtain an understanding of how one feels they are hearing in different situations, and try and understand a patient’s lifestyle in case a hearing aid prescription is required.

Otoscopy

Otoscopy begins with an external inspection of the ear canal. The audiologist can often see some key landmarks on the ear drum, helping them understand the health of the ear canal, ear drum, and the middle ear. If the ear is clear and healthy, the audiologist may see some cursory wax, the long arm of malleus (one of the middle ear bones) and a bright light shining back at them, called the cone of light.

Middle Ear Testing-Tympanometry

Tympanometry allows the audiologist to test the function of the middle ear space and is an important part of the hearing test. A strong peak on the corresponding graph is seen if the ear canal and the middle ear space is clear. Tympanometry allows the audiologist to verify if there is impacting wax, a tear in the ear drum, or fluid behind the ear drum that might be clear and difficult to see upon inspection. While these issues can often be seen using otoscopy, this objective test allows for confirmation.

Pure Tone Audiometry

The pure tone audiometry portion of the hearing test involves the audiologist finding both air conduction and bone conduction thresholds.

Air Conduction

This part of the hearing test is known as the classic beep test. The goal behind it is to find the softest sounds one can hear between 250-8000 kHz. A beep will be played, and the patient will be asked to indicate whether or not the beep was heard, usually by saying ‘yes’ or by pushing a button. The beeps will start off audible and will become very soft as the hearing test progresses. One might think they are falsely hearing the beeps during the hearing test and many patients will feel unsure about their responses. However, the scientific methodology behind the hearing test follows a psychometric function which yields near perfect accuracy within 5dB of the threshold, meaning the test is very accurate and does a good job of measuring hearing (Ref. 1). Obtaining air conduction thresholds helps the clinician understand the softest sounds a patient can hear, as well as lets the audiologist know how the patient hears naturally as sound passes through the ear canal and middle ear space.

Bone Conduction

The second part of the pure tone hearing test involves placing a metal headband with a bone oscillator attached, on the patient’s head. The testing method is the same as the air conduction test; however, the outer and middle ear are being bypassed, and the inner ear, or the cochlea is being stimulated directly with sound. This part of the hearing test informs the audiologist what type of hearing loss (if any) is present. If the cochlea hears better than the outer ear, it could be due to something as simple as wax impaction or fluid in the ear. Another reason could also be related to the ossicles or bones of the middle ear space. This part of the hearing test, combined with tympanometry will let the audiologist know if the hearing loss is reversible with medical intervention. However, if the bone and air line match, this means the hearing loss is not reversible and must be treated with hearing aids.

Speech Testing

Speech testing is used to verify the results of the air and bone conduction tests, or the beep tests, as well as to help the audiologist understand the integrity of the auditory nerve. Speech testing involves the patient hearing words, either through live voice or a recorded audio track, and repeating them back to the audiologist. Two common tests are used: Speech Reception Threshold (SRT) and Word Recognition Scores (WRS). SRTs allow the audiologist to understand the softest level a patient can accurately repeat back speech and helps validate the pure tone hearing test. WRS involves the patient repeating the last word in a sentence back to the audiologist. The words are played at a comfortable volume for the patient. If a patient obtains a score that does not correspond with their hearing test thresholds, this could indicate that the hearing loss involves the inner hair cells or is beyond the cochlea (retrocochlear).

Masking

During speech testing or during the beep tests, the audiologist might play some static sounds in the patient’s ear. The patient will still be instructed to indicate when they’ve heard a beep or will be asked to repeat a word back in the presence of the static noise. Masking is used if one ear hears better than the other, or if the inner ear hears better than the middle ear. The masking sounds are calculated and help keep the ‘better ear’ busy so the audiologist can obtain information for the other ear, or help indicate if the hearing loss has any relation to middle ear function.

Audiogram

All the tests described above help the audiologist create a graph which summarizes the hearing test information discussed. It provides anyone who is reading the graph of the hearing test results an excellent idea of the integrity of the auditory system. The graph shows the softest sounds the patient can hear at all the different frequencies using air and bone conduction thresholds, which are ear specific. The audiogram also shows a summary of the speech scores, otoscopy and middle ear results.