Speed of sound in bubble-free ice.

The speed of sound in a large volume of bubble-free ice was measured with high accuracy using a linear array of six piezoceramic lead zirconium titanate (PZT) receivers. This array was deployed in an approximately 3 m(3) water tank, which was cooled down to -20 degrees C. The freezing process was performed inside a cooling container. Bubble-free ice was obtained using a freeze control unit, which filters and degases the water during the freezing process. A dedicated geometry was used to position PZT receivers and an emitter such that systematic errors were minimized. With this setup the longitudinal and the transverse components of the speed of sound were measured at temperatures between 17 and 0 degrees C in water and between 0 and -20 degrees C in ice with an uncertainty of approximately 0.3%.