The name is absent

driven at different frequencies and amplitudes. ImageJ (rsb.info.nih.gov/ij) was used to
convert the observed displacement into physical distance.

As can be seen in Figure 3b, the displacement varied considerably with
frequency. However, at all frequencies measured (10Hz - 400Hz) the piezo bending
actuator's displacement was greater than 0.1mm if given sufficient voltage. The bending
actuators have several resonant frequencies relating to their length, width, thickness,
and electrical properties. Two resonance peaks can be seen in Fig. ЗА at 30 and 300 Hz.
The frequency of least displacement can be seen at 80 Hz.

Theacousticemissionsofthedeviceweremeasuredinasoundinsulatedroom
with a background noise of 37.3 dB (Fig. 3C). A BK Precision 732A Digital SPL meter
(www.bkprecision.com) was used to take the measurements. The SPL meter used the
IEC651 Type 2 standard, with slow time weighting and a period of 1 second. The bending
actuator was positioned one foot away from the SPL meter, with the flat side facing the
meter. All measurements were at IOOHz or higher, since lower frequencies did not
produce a SignificantSPL relative to the background SPL of the sound insulated room. In
the sound insulated room, the piezos were audible at higher frequencies. However in
the MR scanner subjects wear hearing protection (SPL in MR scanner >90 dB), and are
not able to hear the piezos.

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