Underwater hearing and sound localization with and without an air interface

Area of Science:

• Auditory science
• Underwater acoustics
• Human physiology

Background:

• Underwater hearing acuity and sound localization are reduced compared to terrestrial environments.
• Water in the ear canal lowers resonance frequency, and increased ambient pressure impedes middle ear function.
• Traditional underwater sound localization cues (interaural differences) are diminished due to increased sound velocity and loss of acoustic shadow.

Purpose of the Study:

• To investigate if maintaining an air interface in and around the ear improves underwater hearing sensitivity and sound localization.
• To test the hypothesis that an air interface enhances underwater auditory performance.

Main Methods:

• Ten scuba divers were tested at a 3m depth in open sea using standard or ProEar 2000 masks.
• Pure-tone hearing thresholds (PTHT) and sound localization were assessed using underwater speakers.
• Comparisons were made between dry (air-filled) and wet (water-filled) ear conditions.

Main Results:

• Underwater PTHT were significantly elevated across a wide frequency range (250-6000 Hz) compared to land thresholds.
• No significant differences in PTHT or sound localization error were observed between the regular and ProEar 2000 masks.
• Hearing sensitivity and sound localization did not improve with the presence of air in the ear canal.

Conclusions:

• The presence of air around the pinnae and in the ear canal does not enhance underwater hearing sensitivity or sound localization.
• These findings suggest that bone conduction is the predominant mechanism for underwater hearing.
• The tested air-interface mask did not offer an advantage for underwater auditory perception.