Maximum Output and Low-Frequency Limitations of B71 and B81 Clinical Bone Vibrators: Implications for Vestibular Evoked Potentials.

Abstract

Bone-conducted vestibular evoked myogenic potentials (VEMPs) are tuned to have their maximum amplitude in response to tone bursts at or below 250 Hz. The low-frequency limitations of clinical bone vibrators have not been established for transient, tone burst stimuli at frequencies that are optimal for eliciting VEMPs. Tone bursts with frequencies of 250 to 2000 Hz were delivered to B71 and B81 bone vibrators and their output was examined using an artificial mastoid. The lower-frequency limit of the transducers was evaluated by examining the spectral output of the bone vibrators. Maximum output levels were evaluated by measuring input-output functions across a range of stimulus levels. Both the B71 and B81 could produce transient tone bursts with frequency as low as 400 Hz. However, tone bursts with frequencies of 250 and 315 Hz resulted in output with peak spectral energy at approximately 400 Hz. From 500 to 2000 Hz, maximum output levels within the linear range were between 120 and 128 dB peak force level. The newer B81 bone vibrator had a maximum output approximately 5 dB higher than the B71 at several frequencies. These findings demonstrate that both transducers can reach levels appropriate to elicit bone-conducted VEMPs, but the low-frequency limitations of these clinical bone vibrators limit tone burst frequency to approximately 400 Hz when attempting to stimulate the otolith organs via tone bursts.