How do you test for air conduction and bone conduction hearing?

From the Guidelines

Testing for air conduction and bone conduction hearing should be done using pure-tone audiometry (PTA), which is considered the gold standard for detecting hearing loss, as it measures hearing sensitivity through both bone conduction and air conduction pathways 1.

Key Components of Testing

• PTA is a widely used and reliable tool that establishes the pattern of hearing loss at various frequencies, differentiates the degree of hearing loss, and configuration of the hearing loss.
• Comprehensive diagnostic testing should include the measurement of pure tone thresholds, speech audiometry, tympanometry, and acoustic reflex testing.
• Air conduction thresholds should be measured at 250 to 8000 Hz, and bone conduction thresholds should be measured at 250 to 4000 Hz 1.

Bedside Tests

• Tuning fork tests, such as the Weber and Rinne tests, can be used as a preliminary assessment to distinguish between conductive and sensorineural hearing loss.
• For the Weber test, place a vibrating 512 Hz tuning fork in the middle of the patient's forehead or on top of their head, and ask where they hear the sound.
• For the Rinne test, place a vibrating tuning fork against the mastoid bone, then move it in front of the ear canal, and ask if the sound is heard better via air conduction or bone conduction 1.
• However, it is essential to note that these bedside tests do not supplant formal audiometric testing, and PTA should be performed to obtain accurate and reliable results.

Importance of Accurate Testing

• Accurate audiometric evaluations are essential for proper management of patients with suspected hearing loss.
• PTA can be repeated and compared to previous testing to monitor for changes in hearing loss, and it informs a diagnosis, symptom etiology or pathophysiology, and direction for appropriate treatment 1.

From the Research

Testing for Air Conduction and Bone Conduction Hearing

To test for air conduction and bone conduction hearing, the following methods can be employed:

• Air conduction (AC) testing: This involves measuring the thresholds of sound that can be detected through earphones, typically using pure-tone audiometry 2, 3, 4, 5.
• Bone conduction (BC) testing: This involves measuring the thresholds of sound that can be detected through a bone oscillator, typically placed on the forehead or mastoid bone 2, 3, 4.

Methods for Testing Air Conduction Hearing

Some methods for testing air conduction hearing include:

• Pure-tone audiometry: This involves presenting pure tones of different frequencies through earphones and measuring the threshold of sound that can be detected 2, 3, 4, 5.
• Digits-in-noise (DIN) test: This involves presenting digits in a noisy environment and measuring the ability to detect the digits 6.
• Tone-in-noise detection task: This involves presenting a tone in a noisy environment and measuring the ability to detect the tone 5.

Methods for Testing Bone Conduction Hearing

Some methods for testing bone conduction hearing include:

• Pure-tone bone conduction audiometry: This involves presenting pure tones of different frequencies through a bone oscillator and measuring the threshold of sound that can be detected 2, 3, 4.
• Octave-band filtered sound effect stimuli: This involves presenting sound effects that are spectrally limited to an octave bandwidth centered at specific frequencies and measuring the threshold of sound that can be detected 4.

Considerations for Testing

When testing for air conduction and bone conduction hearing, the following considerations should be taken into account:

• The use of a sound-treated environment is not always necessary, as diagnostic pure-tone audiometry can be performed in natural school environments with sufficient earphone attenuation and real-time monitoring of environmental noise 3.
• The presence of an air-bone gap (ABG) can be predicted with a reasonably high degree of accuracy using AC tests alone, particularly when using a combination of automatically administered pure-tone audiometry and a tone-in-noise detection task 5.
• The size of the ABG, test frequency, and results from multiple test frequencies can affect the sensitivity and specificity of the test battery 5.