Pinna hardness and vibrator placement: Their effects on bone conduction through the pinna

Abstract

This study explores the impact of pinna hardness and vibrator placement on the efficacy of bone conduction through the pinna. Hearing thresholds of twelve participants, all without abnormal pinna conditions, were assessed across frequencies ranging from 250 Hz to 8 kHz, with vibrators positioned at three distinct locations—the front of the ear canal, the earlobe, and behind the cymba concha. Additionally, with a focus on consistent variable manipulation in a controlled experimental scenario, four silicone ear models with Shore hardness values from 0A to 45A were utilized to examine vibrational energy transmission via an accelerometer fixed behind the ear canal. The results indicated that vibrator placement significantly influenced hearing thresholds, a pattern that was also observed in the silicone models. However, the anticipated correlation between pinna hardness and hearing thresholds was not significant within the human sample. This could be attributed to less variability in natural pinna hardness than expected. While it is recognized that pinna hardness varies among individuals, our study reveals a less dramatic variation in pinna hardness among individuals, suggesting that its influence on bone conduction may be less critical than other anatomical factors.