Threshold of hearing by bone conduction. A contribution to international standardization

Area of Science:

• Audiology
• Bioacoustics
• Hearing Science

Background:

• Bone vibrator thresholds are crucial for hearing assessment.
• Understanding vibrator placement effects is vital for accurate bone conduction thresholds.
• Standardized measurements ensure reliable audiological evaluations.

Purpose of the Study:

• To determine equivalent threshold force levels using a specific bone vibrator (Präcitronic KH 70).
• To compare vibrator performance when applied to the mastoid versus the forehead.
• To analyze threshold force levels across a wide frequency range (125 Hz to 8000 Hz).

Main Methods:

• Threshold measurements were conducted on 25 otologically normal young adults (50 ears).
• The Präcitronic KH 70 bone vibrator was applied to both the mastoid and forehead.
• Equivalent threshold force levels were measured using an artificial mastoid (B & K 4930) with masking of the non-test ear.

Main Results:

• For mastoid placement, threshold force levels decreased from 125 Hz to 2000 Hz, then increased and stabilized from 4000 Hz to 8000 Hz.
• Forehead application consistently yielded higher equivalent threshold force levels by approximately 11 dB across the tested frequencies.
• A notable decrease of about 13.5 dB/octave was observed between 125 Hz and 2000 Hz for mastoid placement.

Conclusions:

• Placement site significantly impacts bone vibrator threshold force levels.
• Forehead application requires higher force levels compared to mastoid placement for equivalent audiological results.
• These findings contribute to understanding bone conduction measurement variability and optimizing audiological testing protocols.