Terfenol-D tooth phone performance characterization and optimization

Abstract

A Terfenol-D transducer has been developed for use as a tooth phone with both sensing and actuating capabilities by Audiodontics, Inc. This research focuses on characterizing the sensitivity of the tooth phone’s magnetostrictive Terfenol-D rod performance in both sensor and actuator modes to changes in the initial prestress of the device. A test apparatus was designed to allow prestress variability while operating the transducer as either a sensor or an actuator. To assess the sensor-mode performance, a force-feedback loop control system was used to excite the tooth phone with a constant force from a mechanical shaker at the tooth–tooth phone interface surface while measuring the voltage generated in the transducer’s coil. The shaker was driven with a 200Hzto7kHz swept sine at various dynamics force loadings for prestresses ranging from 0.25to3.5ksi. The results indicate a prestress of 2ksi offers the best sensor-mode performance. To assess the actuator performance, a accelerometer was attached to the tooth–tooth phone interface surface and output acceleration was recorded while sweeping the tooth phone excitation frequency from 200Hzto7kHz with zero-to-peak voltages of 0.1, 0.3, and 0.5V. The prestress settings were varied from 0.3to3.25ksi. As an actuator, no prestress offered a significant broadband performance advantage. Finally, comparisons were made of the tooth phone and an accelerometer for measuring tooth vibrations induced during humming. They perform similarly and capture much of the frequency content found in concurrently recorded microphone data.