High frequency audiometry

What Is High Frequency Audiometry?

A normal cochlea hears 20,000 frequencies. A standard audiogram will only test eight specific frequencies out of these! (250, 500, 1000, 2000, 4000, 6000 and 8000 Hertz). The ear is therefore infinitely more complex than what we can evaluate. However, we can increase the number of frequencies tested thanks to High Frequency Audiometry (HFA).

High Frequency Audiometry is a specialized hearing test that measures your ability to hear very high-pitched sounds, those in the range 8,000 to 20,000 Hertz. This type of audiometry is particularly useful because high-frequency hearing loss can be an early indicator of various conditions (occurs earlier than the lower frequency hearing loss) and can affect certain aspects of hearing, such as understanding speech in noisy environments.

The test is conducted similarly to regular audiometry: you will wear headphones and listen to a series of tones at different high frequencies and volumes, and you'll be asked to indicate when you can hear each tone. However, the tones used are higher-pitched than those in standard tests. 

Differences Between High Frequency Audiometry and Regular Audiograms

While both HFA and regular audiograms measure your hearing ability, they focus on different frequency ranges. A standard audiogram tests frequencies from 250 Hz to 8000 Hz, which covers the range of most everyday sounds, including speech. High Frequency Audiometry, on the other hand, extends this range to include frequencies in the range of 8,000 to 20,000 Hz.

The primary difference lies in the purpose and application: regular audiograms are used for general hearing assessments, while HFA is often used to detect early signs of hearing damage in various populations that are susceptible to hearing loss (patients undergoing chemotherapy, factory workers), and diagnose specific hearing conditions that might not be apparent at lower frequencies.

 

Why Your Clinician Might Recommend High Frequency Audiometry

High frequency audiometry is typically used either:

1) in patients who have normal results on a regular hearing test but report auditory symptoms nonetheless, or

2) in individuals at risk of hearing loss

Common situations would include: 

• Early detection of age-related hearing loss, known as presbycusis, which often starts at higher frequencies;
  
  
• Monitor the effects of ototoxic medications (medications toxic and damaging to the ear), such as certain chemotherapy drugs or antibiotics, that are known to affect high-frequency hearing;
  
  
• Evaluation of tinnitus (ringing in the ears) in someone with a normal hearing test or a tinnitus that involves high-pitched sounds;
  
  
• Early detection of noise-related hearing loss in individuals with history of noise exposure (musicians, factory workers, etc.);
  
  
• Musicians and individuals in certain professions might also undergo HFA to ensure their hearing remains optimal in the high-frequency range.

By testing the high-frequency range, your audiologist or ENT can identify early-stage hearing loss that might otherwise go unnoticed, allowing for timely interventions, like hearing protection or adjustments in medication, to prevent further damage. Essentially, we would like to catch hearing loss before it impacts lower pitches and speech perception

Interpreting High Frequency Audiometry Results

When interpreting a high frequency audiogram, the basic principles remain the same as with a standard audiogram (see this article here for more information), but we are focusing on frequencies above 8,000 Hz. On the graph, the horizontal axis (x-axis) still represents the frequency (or pitch) of sounds, but instead of lower to mid-range pitches, it will show higher pitches up to 20,000 Hz. The vertical axis (y-axis) represents the hearing threshold in decibels (dB): the lower the hearing levels, the worse the hearing. Normal hearing in the high-frequency range is typically between 0-25 dB, similar to standard audiometry.

A high frequency audiogram is considered abnormal if the threshold for detecting these high-pitched sounds shifts beyond 25 dB. A gradual downward slope in the high-frequency range (e.g., starting around 8,000 Hz or higher) may indicate early signs of noise-induced hearing loss, ototoxicity, or age-related hearing loss (presbycusis). In severe cases, the threshold might drop significantly (above 40 dB), indicating a more advanced stage of high-frequency hearing loss. 

Limitations of High Frequency Audiometry

Technical Challenges: High frequency audiometry faces technical difficulties in producing and measuring these higher frequencies between 16,000 and 20,000 Hz accurately. The equipment used for HFA lacks the standardization found in conventional audiometry equipment, leading to possible differences in results between various systems.

Lack of Normative Data: There is a limited amount of detailed baseline ("normative") data for high-frequency sounds, particularly when contrasted with the abundant data available for standard audiometry. This makes it challenging to interpret HFA results consistently across different populations and age groups.

Age-Related Factors: High frequency hearing naturally declines with age, making it difficult to establish consistent "normal values" for older populations. This further complicates the interpretation of HFA results.

Frequently Asked Questions About High Frequency Audiometry

Q: How long does the test take?
A: The duration of the test can vary, but it usually adds about 10 minutes to a regular hearing test.

Q: Can I prepare for the test?

A: There's no special preparation needed for HFA. However, it's a good idea to avoid exposure to loud noises before the test (noise rest), as this could temporarily affect your hearing and the test results.