Acoustic basis of tuning fork tests

Objectives: To obtain pilot data to determine the feasibility of supporting or refuting a theory regarding lateralization of sound in conductive heari ng loss and to describe the application of this theory to other tuning fork tests. Design: Controlled audiometric testing with and without a conductive hearin g loss. Setting: A tertiary medical centre. Methods: Sound pressure levels in external auditory canals were measured du ring presentation of 40- and 50-dB bone-conducted stimuli. Measurements wer e taken from five normal male subjects before and after inducing a conducti ve hearing loss. Outcome Measures: If sound intensity in the car canal was greater in the un obstructed ear canal than the obstructed car canal, the hypothesis was supp orted. The number of subjects required to provide definitive proof was calc ulated from the measured intensity difference with and without the conducti ve loss and the intrasubject variability of sound intensity measurements. T he applicability of the theory to other tuning fork tests and auditory phen omena was explored. Results and Conclusions: A total of 600 subjects would be required to provi de evidence to support our theory using this method. The acoustic impedance mismatch-reflected sound theory could be applied to other tuning fork test s, but until further proof is available, it must be considered only a theor y.