Introduction to Air Conduction (AC) and Bone Conduction (BC)

Air conduction (AC) and bone conduction (BC) are two essential techniques utilized in audiological assessments to evaluate various aspects of hearing functionality. AC involves sound waves traveling through the air, while BC bypasses the outer and middle ear, directly transmitting sound through bone vibrations.

Understanding Air Conduction (AC)

Timing and Mechanism

AC begins with sound waves entering the outer ear and moving through the middle ear, ultimately reaching the inner ear and cochlea. This pathway is fundamental for the majority of individuals with normal hearing.

Evaluation and Effectiveness

For individuals with normal hearing, AC thresholds tend to be lower in intensity because the entire auditory system is functioning effectively. AC is generally more effective for overall hearing assessment due to its comprehensive evaluation.

Understanding Bone Conduction (BC)

Method and Mechanism

BC involves transmitting sound through the skull, bypassing the outer and middle ear. This technique is often employed using a tuning fork placed on the mastoid bone or forehead. BC provides direct stimulation of the cochlea via bone vibrations.

Intensity and Sensitivity

BC often requires less intensity than AC during pure tone audiometry. This is because it directly stimulates the cochlea, making it more sensitive to vibrations, particularly in cases of conductive hearing loss where sound transmission is impaired.

Why Air Conduction (AC) is Superior

AC is better for overall hearing assessment as it evaluates the entire auditory pathway. This comprehensive evaluation allows for better sound amplification and amplification clarity, making it the preferred method for a full hearing assessment.

Why Bone Conduction (BC) Requires Less Intensity

BC requires less intensity because it bypasses potential issues in the outer and middle ear, directly stimulating the inner ear. This direct stimulation can be more easily detected by the ear, making it useful for assessing inner ear and auditory nerve function.

Applications in Clinical Practice

Both AC and BC are crucial for differentiating between types of hearing loss—conductive versus sensorineural—and providing a comprehensive understanding of a person's hearing abilities. They work together to offer a complete picture of auditory function.

Comparisons and Clinical Implications

The Rinne test and pure tone audiometry each target different aspects of hearing. The Rinne test, an uncalibrated method, finds that AC sound is typically perceived longer than BC vibrations. Pure tone audiometry, on the other hand, reveals that BC can be equal to or better than AC, depending on the context and calibration.

In a normal hearing individual