In this article, we will explore the concept of audiometry, the different types of audiometry tests, their interpretation, and the professionals involved in conducting these tests.

Overview:

What Does Audiometry Test?

Audiometry is a comprehensive assessment of an individual's hearing abilities. It aims to measure the softest sounds a person can hear at different frequencies, known as pure tone audiometry, and assess their ability to understand speech, known as speech audiometry.

These tests provide valuable information about the degree, configuration, and type of hearing loss, helping healthcare professionals develop effective treatment plans.

What Are the Two Types of Audiometry?

There are two main types of audiometry, namely Pure Tone Audiometry and Speech Audiometry. 
1. Pure Tone Audiometry:
Pure tone audiometry measures an individual's hearing thresholds at various frequencies, typically ranging from 125 Hz to 8,000 Hz. Hearing thresholds for both air-conducted and bone-conducted sounds are obtained. 

Hearing via air conduction means that:
  • Sound waves travel through air and along the ear canal to vibrate the eardrum.
  • This vibration then moves the ossicles (link to article on The Ossicles), the three tiny bones in the air-filled middle ear cavity to vibrate the oval window (OW).
  • The vibration of the OW then transfers the sound through the fluid-filled inner ear and stimulates the hearing nerve. 

Hearing via bone conduction means that: 
  • Sound waves in the air hit the bones of the skull, stimulating the hearing nerve directly, bypassing the air-filled outer and middle ear.
Pure tone audiometry is widely used in both children and adults. It forms the foundation of any audiological evaluation and aids in diagnosing and managing various hearing disorders since it provides information about the degree and configuration of hearing loss.

A type of pure tone audiometry is Play audiometry. Conditioned play audiometry is specifically designed for young children who may not respond to conventional audiometry tests. It involves engaging the child in a game-like activity, where they are asked to perform a task each time they hear a sound. This approach helps assess hearing thresholds and provides valuable information for pediatric audiological evaluations.
2. Speech Audiometry:
Speech audiometry evaluates a person's ability to understand speech. It is used alongside pure tone audiometry to assess the patient's functional hearing abilities and determine the impact of hearing loss on speech perception.

It involves the presentation of recorded or live speech materials at varying volumes. The patient is asked to repeat words or sentences, and their responses are recorded.

Speech audiometry helps determine the patient's speech reception threshold (SRT) and word recognition score (WRS). SRT measures the lowest volume at which the individual can understand speech, while WRS assesses the percentage of correctly repeated words.

What is the Normal Audiometry Range?

The normal audiometry range is based on the hearing thresholds of individuals with typical hearing. In adults, normal hearing is defined as thresholds of 20 decibels (dB) or better across all frequencies tested.1

For children, the range may be slightly different due to developmental considerations. Any deviation from the normal range suggests the presence of hearing loss.
 
Figure ref: https://www.stgeorges.nhs.uk/wp-content/uploads/2019/03/How-To-Read-Your-Hearing-Test-Results.pdf

What's the Difference Between Audiometry and the Audiogram?

Audiometry and the audiogram are closely related but distinct concepts.

Audiometry refers to the overall process of assessing hearing, including both pure tone and speech tests. It involves the use of specialized equipment and standardized protocols to obtain accurate measurements.
An audiogram, on the other hand, is a graphical representation of the results obtained during the audiometry test. It plots the hearing thresholds at various frequencies on a chart, enabling easy visualization and interpretation of the patient's hearing abilities.1
 
Red = Right ear; Blue = Left ear

Figure ref: https://www.stgeorges.nhs.uk/wp-content/uploads/2019/03/How-To-Read-Your-Hearing-Test-Results.pdf

How to Do An Audiometry Test?

  1. Pure tone audiometry is conducted in a soundproof booth or a quiet room to eliminate ambient noise and ensure accurate measurements. 
  2. You will be seated comfortably and the audiologist will use an audiometer to present tones of different frequencies and varying intensities or loudness.
  3. You will be instructed to respond each time you hear a tone by raising your hand or pressing a button.
  4. First, you will do this while wearing over-the-ear headphones or insert earphones, which determines the softest sounds you can hear via air conduction.
  5. Next, your bone conduction thresholds will be measured via a vibrating transducer placed on the mastoid process, the bone behind your outer ear. 
  6. The test is repeated for each frequency, and the results are recorded on an audiogram. Most commonly, tones at the test frequency are presented at decreasing loudness levels (in 5 or 10 dB steps) until they become inaudible. The tones are then presented at increasing intensity until they become audible and you start responding again. This procedure is known as the Hughson-Westlake method.2

Audiometry Results Explained

Speech audiometry results provide insights into the patient's ability to understand speech at different volumes.

Interpreting pure tone audiometry results requires analyzing the audiogram and considering the patient's responses.

The audiogram provides information about the patient's hearing thresholds at various frequencies, measured in decibels (dB). The lower the threshold, the better the hearing sensitivity.

The configuration or shape of the audiogram (e.g. flat, sloping, or steeply sloping) indicates the type of hearing loss.
In the case of a hearing loss, the difference between the air conduction and bone conduction thresholds on the audiogram provides information about the site of lesion, or where the problem may lie. For example:
Sensorineural Hearing Loss (SNHL):
If air conduction and bone conduction thresholds lie within 5-10 dB of each other on the audiogram, then the hearing loss is considered Sensorineural.
This type of hearing loss is usually permanent and originates in the cochlea or ‘inner ear’.

There are many causes of this type of hearing loss, such as genetics, illness before birth or during childhood, certain medications, damage to the inner ear from an accident or noise damage.2 
Conductive Hearing Loss (CHL):
If the air-bone gap at any frequency is greater than 15 dB, where the bone conduction thresholds are within the normal range but the air conduction thresholds are reduced, this is considered a CHL. This occurs when there is abnormal transmission of sound through the outer or middle ear without damage to the inner ear.

CHL may occur due to wax impaction, otitis media (link to article on Otitis Media), eardrum perforation, ossicular disruption (link to article on the Ossicles), and a foreign body in the ear, among other causes.2
Mixed Hearing Loss:
This is a combination of SNHL and CHL, meaning there is a problem with sound conduction in the outer and/or middle ear and damage to the inner ear structures. This type of hearing loss presents as an air-bone gap, and both air conduction and bone conduction thresholds are reduced below the normal range.

Mixed hearing loss results from many different pathologies, including otosclerosis, a disease in which both the ossicles (CHL) and the inner ear (SNHL) are affected due to abnormal bone growth.2

Screening Audiometry vs. Diagnostic Audiometry

Screening audiometry and diagnostic audiometry serve different purposes. Screening audiometry aims to quickly identify individuals with potential hearing loss and determine if further evaluation is necessary. It is often used in schools, workplaces, primary care settings or online. Click here to take our quick online hearing screening test.

Diagnostic audiometry, on the other hand, involves a comprehensive evaluation of an individual's hearing abilities. It provides detailed information about the type, degree, and configuration of hearing loss, facilitating appropriate management and intervention.

Where to Get an Audiogram?

Audiometry tests are conducted by licensed audiologists or hearing healthcare professionals trained in audiology. These professionals have in-depth knowledge of the auditory system, hearing disorders, and appropriate testing protocols. They possess the expertise to accurately administer the tests, interpret the results, and provide appropriate recommendations for further evaluation or intervention. 

Click here to locate your nearest hearing center.

Summary

Audiometry plays a vital role in diagnosing hearing impairments, determining the type and degree of hearing loss, and guiding appropriate interventions. By conducting pure tone and speech audiometry, audiologists can obtain a comprehensive understanding of an individual's hearing abilities. Understanding the results and interpreting the audiogram provides valuable information for treatment planning and improving the quality of life for those with hearing loss.

Reference:

  1. How to Read Your Hearing Test Results (2019). St Georges Hospital. Retrieved from https://www.stgeorges.nhs.uk/wp-content/uploads/2019/03/How-To-Read-Your-Hearing-Test-Results.pdf on 28 June 2023.
  2. Salmon, M. et al. (2023). Audiogram Interpretation. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK578179/ on 28 June 2023.
The information contained in this article is for educational and informational purposes only. You should not use the information as a substitute for, nor should it replace, professional medical advice. If you have any questions about your health, you should always consult with a physician or other health-care professional.