The MPL sound velocimeter: An instrument for in situ sound velocity measurements in the deep ocean Journal Article uri icon



  • A sound velocimeter designed to measure sound speed to a precision of 1 part in 105 has recently been tested at sea. The device was used in conjunction with a CTD to check agreement with sound speeds computed from popular empirical equations [C.-T. Chen and F. J. Millero, J. Acoust. Soc. Am. 62, 1129–1135 (1977); V. A. DelGrosso, J. Acoust. Soc. Am. 56, 1084–1091 (1974)]. Disagreements will be discussed. High-precision travel-time measurement is achieved through use of a phase-comparison technique. For this purpose, the device determines the number of cycles of the acoustic signal between the transmitted pulse and received echo, adjusting the frequency until the echo and transmitted pulse are in phase. The travel time is the product of the signal period and the number of cycles between the outgoing and incoming pulses. The velocimeter’s capability of measuring travel time at several different frequencies near 4 MHz serves as a check on the timing consistency, since the travel time should be independent of frequency over this narrow range. The total distance traveled by the pulse is about 8.6 cm. With proper calibration, this pathlength can be known to a precision of 1 part in 105.

publication date

  • November 1, 1997

has restriction

  • closed

Date in CU Experts

  • June 3, 2021 10:36 AM

Full Author List

  • Sweeney AD; Spiess FN; Boegeman DE; Jabson DM; Zimmerman R

author count

  • 5

Other Profiles

International Standard Serial Number (ISSN)

  • 0001-4966

Additional Document Info

start page

  • 3119

end page

  • 3119


  • 102


  • 5_Supplement