High precision oscillators for absolute sound speed measurements in the laboratory and in the free ocean

This paper deals with Kroebel's method of measuring the sound velocity in liquids particularly in water and seawater, a so called frequency method, using an oscillator with continuous waves. It is a short report on the work that has been carried out mainly with the aim to develop new high precision instrumentation to improve standard tables of sound velocity data and to get better knowledge about phenomena in the sea causing the build up of fine structured layers and regions of different sound velocities. The accuracy of the values from the absolute sound velocity measuring device in the laboratory has proved to be1cm/s to1,5cm/s. The sensor developed for free field applications in the ocean using also Kroebel's method has shown a reproducibility of data of about 4 cm/s.