Occlusion effect in bone conduction pure tone and speech audiometry.

Two experiments were conducted to determine the occlusion effect (OE) for pure tone and spondee stimuli. Results of experiment I using mastoid placement and unilateral occlusion yielded a mean OE for bone conduction speech reception thresholds of 4.67 dB, which was in agreement with the average OEs of 0.50, 1.0 and 2.0 kHz, or simply the same as the OE for 1.0 kHz. However, the magnitude of the observed OEs for test frequencies of 0.25 to 4.0 kHz was considerably less than the OEs reported in previous investigations. In an attempt to explain this discrepancy, experiment II used unilateral and bilateral occlusion with mastoid and forehead placement for pure tone stimuli. Significant differences (p less than 0.05) were found between OEs obtained with mastoid versus forehead placement and for unilateral versus bilateral occlusion.