Research leading to a significant improvement in the signal-to-noise sensitivity of wideband acoustic/ultrasonic contact displacement sensors for wood and polymers is described. Design principles for such high-sensitivity sensors are reviewed. Comparisons of response between ceramic and polymer piezoelectric elements are made on low modulus specimens, A new, practical high-sensitivity sensor is characterized and its signal-to-noise sensitivity is compared to that of an existing commercial wide band displacement sensor. The comparisons were made for polymer, maple, and redwood samples. Optimization of the piezoelectric element in the new sensor is considered. The typical increased sensitivity of the new sensor is about 30 dB over the existing commercial sensor
