Audiometry

Audiologist, 2015

Audiometry is the science of measuring hearing acuity for variations in sound intensity and pitch and for distinguishing between sound sources. This measurement is not a simple process of how well a person can hear, but rather a detailed assessment of an individual's hearing capacity, often resulting in a detailed audiogram. Audiometry is crucial in diagnosing and treating hearing loss, understanding speech perception, and occupational health.

Types of Audiometry

There are several types of audiometry tests, each designed to measure different aspects of hearing. The most common include:

• Pure Tone Audiometry (PTA): This test measures an individual's ability to hear sounds of varying pitches (frequencies) and intensities (loudness). The results are plotted on an audiogram, which is a graph displaying the softest sounds a person can hear at different frequencies.
• Speech Audiometry: This assesses the ability to recognize speech, including speech reception threshold (SRT) tests and speech discrimination tests. It helps in understanding how well a person can understand speech in quiet and noisy environments.
• Impedance Audiometry: Also known as tympanometry, this test measures the movement of the eardrum and the conduction bones in the middle ear. It is useful in identifying issues related to middle ear pressure, fluid, and ear bone chain problems.
• Otoacoustic Emissions (OAEs): This test measures sounds given off by the inner ear when responding to a sound. OAEs are often used in newborn hearing screening programs to detect congenital hearing loss.

Clinical Applications

Audiometry is used in various clinical settings, including:

• Diagnosis of Hearing Loss: Audiometry is the cornerstone in diagnosing different types and degrees of hearing loss, from mild to profound.
• Hearing Aid Fitting: Audiograms provide essential information for the selection and fitting of hearing aids.
• Monitoring of Hearing Loss: Regular audiometric tests can monitor the progression of hearing loss in patients.
• Occupational Health: Audiometry is used to assess the impact of noise exposure in the workplace and to implement hearing conservation programs.

Procedure

During an audiometry test, the patient is exposed to a range of sounds through headphones or earplugs connected to an audiometer. The audiologist adjusts the pitch and loudness of the sounds, and the patient indicates when they can hear them. The results are then charted on an audiogram.

Audiogram Interpretation

The audiogram is a graph that plots an individual's hearing sensitivity across various frequencies. The vertical axis represents the intensity (loudness) of sound measured in decibels (dB), and the horizontal axis represents frequency (pitch) measured in hertz (Hz). Thresholds of hearing are marked for each ear, indicating the softest sound that can be heard at each frequency.

Challenges and Limitations

While audiometry is a powerful tool in assessing hearing, it has its limitations. The accuracy of the results can be affected by the patient's ability to understand the test instructions, their response time, and the presence of tinnitus or other auditory phenomena. Additionally, audiometry primarily assesses peripheral hearing function and may not fully capture central auditory processing disorders.

Conclusion

Audiometry is a fundamental tool in the field of audiology, providing invaluable information for the diagnosis and management of hearing loss. Its application spans clinical settings, occupational health, and research, making it an essential component of auditory health services.