Bone-conducted auditory brainstem-evoked responses and skull vibratory velocity measurement in rats at frequencies of 0.5–30 kHz with a new giant magnetostrictive bone conduction transducer

Abstract

Conclusions. A new giant magnetostrictive bone conduction transducer (GMT) measuring 8 mm (length) by 2 mm (diameter) is capable of outputting sounds over a wider range of frequencies than conventional electromagnetic transducers (EMTs). The GMT can vibrate the rat skull about 3–100 times faster than the EMT, especially above 2 kHz. Objectives. Since the GMT can generate high sound quality and output sounds above 10 kHz, we investigated the width of the frequency response of the GMT and evaluated its mechanical performance. Materials and methods. We chose Wistar rats to estimate the GMT performance by measuring the bone-conducted ABR and the skull vibratory velocity because their hearing frequency range extends from 0.15 kHz to 67 kHz. We also measured the bone-conducted auditory brainstem responses (ABRs) and the skull vibratory velocity of rats with the EMT. Skull vibratory velocity was measured with a laser Doppler vibrometer (LDV). Results. The skull vibratory velocity at the ABR threshold obtained with each transducer was within the −35 to −50 dB range (0 dB re 1 mm/s). When 1 Vpp was applied to each transducer, the GMT had a higher velocity at frequencies of 2–30 kHz, and the EMT at frequencies of 0.5–1 kHz.