The Tuning Fork Examination: Are You Performing It Correctly?

Abstract

Objectives: The tuning fork remains a useful diagnostic tool in modern otolaryngology practice. Two important variables help describe the sound generated by the tuning fork: frequency and amplitude. We sought to determine whether the manner in which a tuning fork is activated affects its vibrational response. Methods: A Polytec OFV-5000 single point laser Doppler vibrometer was used to obtain direct velocity measurements after activation of 256 Hz, 512 Hz, and 1024 Hz tuning forks with several striking methods: striking the parietal bone, striking the pisiform bone, striking a wood table, and striking a metal surface. Each method was tested using three separate subjective intensities: softly, medium force, and significant force. Data were analyzed using the Polytec Vibrometer Software to produce a velocity spectrum and measurements of frequency and velocity amplitude. Results: The predominant frequency of motion of all tuning forks was their expected fundamental frequency. Additional nonharmonic frequencies were recorded when striking the 256 Hz and the 512 Hz tuning forks against metal or wood. The aberrant frequencies were of lower intensity relative to the fundamental frequency of the tuning fork. Conclusions: No additional frequencies were seen with activation on the head or pisiform bone or with the 1024 Hz fork using any method. For the 256 Hz and 512 Hz tuning forks, striking a hard surface produced additional and potentially misleading frequencies. As some providers use this test to guide surgical candidacy decisions in stapes surgery, this could have significant impact in clinical decisions.