Bone conduction audiometry Aim: To determine the type of hearing loss by testing the sensorineural mechanism. Bone conduction actually works through three mechanisms: Distortion of the skull bones Activity of the ossicles Movement of the air column in the outer ear canal.

Issues with bone conduction Placement: Mastoid or forehead? Which ear is being tested? Occlusion effect (Table 4.2, page 89) Tactile responses Procedure for testing similar to AC Record thresholds in audiogram using appropriate symbols.

Audiogram interpretation Based on AC and BC thresholds and relationship between them. Difference between AC and BC: Air-Bone Gap (ABG). Shows amount of conductive component If both AC and BC within normal limits: Normal hearing If AC thresholds elevated, BC normal: ? If both AC and BC elevated, but ABG less (≤10 dB): ? If both AC and BC elevated, but ABG high (>10 dB): ?

Cross-hearing Response by the non-test ear. Inter-aural attenuation (IA; Table 4.3, page 96/105) Cross-hearing for AC occurs when ACTE – IA ≥ BCNTE