The Occlusion Effect and Ear Canal Sound Pressure Level

Area of Science:

• Audiology
• Hearing Science
• Bioacoustics

Background:

• The occlusion effect describes the change in bone-conduction hearing sensitivity when the ear canal is covered.
• Understanding the relationship between external auditory canal sound pressure and bone-conduction audibility is crucial for audiological assessments.

Purpose of the Study:

• To compare changes in bone-conduction audibility with variations in external auditory canal sound pressure during ear occlusion.
• To investigate the influence of stimulation site (mastoid vs. frontal bone) on the occlusion effect.

Main Methods:

• Fifteen participants with normal middle ear function were tested.
• Pure tones (250, 500, 1000 Hz) were delivered via bone-conduction oscillator on the mastoid and frontal bone.
• Sound pressure levels in the external auditory canal were measured in occluded and unoccluded conditions.

Main Results:

• Ear canal sound pressure levels were significantly higher with ear occlusion across all tested frequencies and stimulation sites.
• Bone-conduction hearing thresholds improved (lower intensity needed for detection) in the occluded condition.
• The occlusion effect was slightly attenuated when bone-conduction stimulation was applied to the frontal bone compared to the mastoid.

Conclusions:

• Ear canal occlusion enhances bone-conduction audibility, likely due to increased sound pressure within the occluded canal.
• The location of bone-conduction stimulation influences the magnitude of the occlusion effect, with frontal bone stimulation showing a reduced effect.