The dynamic range of TMJ sounds.

Area of Science:

• Biomedical Engineering
• Otolaryngology
• Dentistry

Background:

• Temporomandibular joint (TMJ) sounds, such as clicks, are clinically significant indicators of joint dysfunction.
• Accurate measurement of TMJ sound amplitudes is essential for diagnosis and monitoring.
• Previous recording methods may be limited by ambient noise and insufficient dynamic range.

Purpose of the Study:

• To investigate the effect of sealing the ear canal on the sound pressure level (SPL) of TMJ sounds.
• To test the hypothesis that sealing the meatus improves the recording of TMJ clickings.
• To assess the suitability of 24-bit analog-to-digital (A/D) conversion for capturing the dynamic range of TMJ sounds.

Main Methods:

• Bilateral recordings of 249 TMJ clickings from three subjects.
• Utilized sampling rates of 48 or 96 kHz and 24-bit A/D conversion.
• Compared recordings with and without the ear canals sealed using silicone putty.

Main Results:

• The peak-to-peak equivalent sound pressure level (peSPL) was significantly higher (P < 0.001) when the ear canal was sealed.
• Mean differences in peSPL ranged from 8.3 to 24.9 dB.
• The signal-to-noise ratio improved without increasing electronic noise.
• The dynamic range of clicking sounds (62 dB) exceeded that of a 16-bit sound card.

Conclusions:

• Sealing the ear canal is an effective method for increasing the SPL and improving the signal-to-noise ratio of TMJ sound recordings.
• 24-bit A/D conversion is necessary to capture the full dynamic range of TMJ sounds, particularly in cases of disc displacement with reduction.
• Future research should establish normative peSPL values for clinical application.